Hearing impairment among adult foreign-born and Swedish-born individuals: A national Swedish study.

OBJECTIVES: To analyze the risk of hearing impairment in adult first-generation immigrants, i.e., foreign-born individuals as compared to Swedish-born individuals. STUDY
DESIGN: A register-based study follow-up study.
METHODS: A nationwide study of individuals 25 years of age and older (N = 5 464 245; 2 627 364 men and 2 836 881 women) in Sweden. Hearing impairment was defined as at least one registered diagnosis in the National Patient Register between January 1st, 1998 and December 31st, 2015. Cox regression analysis was used to estimate the relative risk (hazard ratios (HR) with 95% confidence intervals (CI)) of incident hearing impairment in foreign-born compared to Swedish-born individuals. Cox regression models were stratified by sex and adjusted for age, comorbidities, and socioeconomic status.
RESULTS: A total of 244 171 cases (124 349 men and 119 822 women) of hearing impairment were registered. Hearing impairment risk expressed as fully adjusted HRs (99% CI) was somewhat lower among immigrant men 0.95 (0.92-97) but not among immigrant women 0.97 (0.95-1.00), with significantly higher fully adjusted HRs among men and women from Asia, and Eastern Europe, and women from Africa.
CONCLUSIONS: We observed a somewhat lower risk of hearing impairment among foreign-born men, but there was a higher risk among men and women from some regions.

1. Introduction

Globally, hearing loss is estimated to be “the fourth most leading contributor to years lived with disability” [1]. The causes of deafness and hearing impairment differ by world region. Furthermore, the risk of hearing impairment also varies in different regions of the world, with the lowest risks found in high income countries, i.e. mostly Western and Northern Europe and Northern America [2]. By contrast, higher risks are found in Central and Eastern Europe, Sub-Saharan Africa, Latin America, and Asian regions, mostly south Asia. Globally, half a billion people are estimated to exhibit a disabling hearing loss, i.e. around 7% of the world’s population [1, 2]. An American study found that the prevalence of deafness or serious difficulty hearing was approximately 6% [3].

Several comorbidities have been associated with hearing loss including visual impairment, mobility restrictions, psychosocial health problems, diabetes, cardiovascular diseases, stroke, arthritis, cancer [4], dementia, depression, and falls [5]. Lower socioeconomic status is often associated with a higher risk of several diseases, both at the individual [6] and neighborhood level [7]. Lower socioeconomic status has also been found to be associated with hearing impairment [3]. Aside from lower socioeconomic status, not being married is also a risk factor for several morbidities and higher mortality, especially among men [8], and may therefore also be associated with hearing loss.

As regards immigrants, hearing impairment may be challenging when learning the language and culture of a new country, which calls for attention and motivated us to conduct this study. Identifying hearing impairment is also important as correction with hearing aids and rehabilitative services have been shown to increase well-being and quality of life [9]. An American study found differences between Asian groups of elderly foreign-born people, with a higher risk of deafness among Hawaiians/Pacific Islanders, Filipinos, and non-Hispanic whites than among Chinese immigrants [10]. Sweden is a country with a high proportion of both first- and second-generation immigrants but we have not been able to find any previous Swedish studies on hearing impairment among foreign-born individuals (i.e., first-generation immigrants) that were conducted in the country. We have previously shown that, among second-generation immigrants, boys with parents from Asia have a higher risk of extended sensorineural hearing impairment [11].

The aim of this study was to compare the risk of hearing impairment in immigrant men and women with Swedish-born men and women. Based on earlier findings [2], we hypothesized that some immigrant groups, including non-Western regions and Central and Eastern Europe, may have an increased risk of hearing impairment, which is important to investigate as it may affect immigrants’ integration in Sweden.

2. Methods

2.1 Design

We used the Swedish Total Population Register and the National Patient Register (NPR) for the study. The Total Population Register, which is based on unique personal identification numbers, includes data on all individuals registered in Sweden, [12, 13]. Individuals aged 25 years of age and older were included to compare foreign-born individuals to Swedish-born. The follow-up period ran from January 1st, 1998 until hospitalization/out-patient treatment of a diagnosis of hearing impairment, death, emigration, or the end of the study period on December 31st, 2015, whichever, came first. Nationwide out-patient diagnoses were included from 2001 onwards from specialist open care but not primary health care as these diagnoses are not included in the NPR. The unique pseudonymized serial number for each individual was used to avoid double-counting.

2.2 Outcome variable

Hearing loss based on ICD-10 codes included the following conditions: Conductive and sensorineural hearing loss (H90), other hearing loss (H91), and noise-induced hearing loss (H83.3). In a categorization of different diagnoses of hearing loss we included the following subgroups: “Conductive hearing impairment” (H90.0-H90.2); “Extended sensorineural hearing impairment” (H90.3-H90.5), also including ototoxic hearing loss (H91.0), presbycusis (H91.1); “Noise-induced hearing impairment” (H83.3); and finally “Other hearing impairment” (H91.2-H91.9), also including mixed etiology (H90.6-H90.8).

2.3 Comorbidities

We identified the following comorbidities (with ICD-10 codes) based on the existing literature [4, 14]: Tinnitus (H93.1); Intracranial trauma (S06); Malignant brain tumor (D32, D33, C70, C71); Stroke (I60-I69); Hypertension (I10-I19); Coronary Heart Disease (CHD; I20-I25); Chronic Obstructive Pulmonary Disease (COPD; J40-J47); Cancer (C00-C97, with C70 and C71 excluded, and categorized into the brain tumor group); Diabetes (E10-E14); Arthropathies (M00-M25, also including Arthrosis M15-M19); Dementia (F00-F03, F10.7A, G30, G31.8A); Depression (F32-F33); and Visual impairment (H54).

2.4 Demographic and socioeconomic variables

Age was used as a continuous variable in the analysis.

Marital status was defined as married or not.

Educational attainment was categorized as ≤9 years (partial or complete compulsory schooling), 10–12 years (partial or complete secondary schooling) and >12 years (attendance at college and/or university).

Geographic region of residence was included in order to adjust for possible regional differences in health care access and was categorized as (1) large cities with surrounding regions, (2) southern Sweden (southern and middle part of Sweden) and (3) northern Sweden (the five most northern counties). Regarding regions in Sweden, the urbanicity differs with many sparsely populated parts in northern Sweden with, in many cases, long transportation routes and also poorer access to ophthalmologists. Large cities were defined as municipalities with a population of >200,000 and comprised the three largest cities in Sweden: Stockholm, Gothenburg and Malmö.

The analyses were stratified by sex because men and women experience different types of environments, including those related to occupation, and also have different health care seeking patterns [15].

2.5 Neighborhood deprivation

Neighborhood socioeconomic status (NSES) has been shown to be an important socioeconomic factor for several health outcomes. The NSES was derived from Small Area Market Statistics (SAMS). The neighborhoods were derived from Small Area Market Statistics (SAMS), which were originally created for commercial purposes and pertain to small geographic areas with boundaries defined by homogenous types of buildings. The average population in each SAMS neighborhood is approximately 2000 people for Stockholm and 1000 for the rest of Sweden. A summary index was calculated to characterize neighborhood-level deprivation. The neighborhood index was based on information about female and male residents, aged 20 to 64 years of age, because this age group represents those who are among the most socioeconomically active in the population (i.e. a group that has a stronger impact on the socioeconomic structure in the neighborhood compared to children, younger women and men, and retirees). The index was based on the following four variables: low educational status (<10 years of formal education); income from all sources, including interest and dividends, that is (<50% of the median individual income); unemployment (excluding full-time students, those completing military service, and early retirees); and receipt of social welfare [6, 7]. This index was categorized into four groups: more than one standard deviation (SD) below the mean (low deprivation level or high SES), more than one SD above the mean (high deprivation level or low SES), and within one SD of the mean (moderate SES or moderate deprivation level) used as the reference group, and also unknown neighborhood SES.

2.6 Statistical analysis

Baseline data are presented with continuous variables as mean and standard deviations and categorical variables as counts and percentages. We used Cox regression analysis to estimate the relative risk (hazard ratios (HR) with 95% confidence intervals (CI)) of incident hearing impairment in separate groups of foreign-born individuals compared to the control group, i.e. Swedish-born, during the follow-up time. We used an open cohort design and as Cox regression was used in the statistical analysis, only the first event was registered. Risk time was calculated until the event and those who died or emigrated were censored. All analyses were stratified by sex. Three models were used: Model 1 with adjustment for age and region of residence; Model 2 with adjustment for age, region of residence, educational level, marital status and neighborhood SES; this was to examine to what extent SES explained the association between country of birth and incident hearing impairment; and Model 3 as Model 2 but with the inclusion also of relevant comorbidities (tinnitus, intracranial trauma, malignant brain tumor, stroke, CHD, COPD, cancer, diabetes, arthropathies, dementia, depression, and visual impairment); this was to examine if other diagnoses explained the association between country of birth and hearing impairment.

We also sub-divided into groups of hearing impairment, i.e. into “Conductive hearing impairment”, “Extended sensorineural hearing impairment”, “Noise-induced hearing impairment”, and “Other hearing impairment”.

In a sensitivity analysis, we adjusted for time in Sweden for immigrants. In addition, we also analyzed the number of separate diagnoses for men and women.

2.7 Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent was not applicable, as the study was based on pseudonymized data from registers.

The study was approved by the Regional Ethical Review Board in Lund.

The authors are not allowed to share the used data from the data sources being used due to legal restrictions in Sweden.

3. Results

3.1 Main results

In total (Table 1), 5 464 245 individuals were included (2 627 364 men and 2 836 881 women), of which 244 171 individuals had a registered diagnosis of hearing impairment (124 349 men and 119 822 women).

Table 1

Study population and number of cases with hearing impairment categorized by sex.

	Men				Women
	Whole Population		Hearing impairment		Whole Population		Hearing impairment
	No.	%	No	%	No.	%	No	%
Total population	2627364		124349		2836881		119822
Age (years)
25–39	811202	30.9	16929	13.6	836038	29.5	16449	13.7
40–49	513920	19.6	23376	18.8	527349	18.6	21001	17.5
50–59	532459	20.3	38405	30.9	535011	18.9	31143	26.0
≥ 60	769783	29.3	45639	36.7	938483	33.1	51229	42.8
Educational level
≤ 9	887937	33.8	41982	33.8	991397	34.9	41592	34.7
10–12	712203	27.1	33223	26.7	815714	28.8	38872	32.4
> 12	1027224	39.1	49144	39.5	1029770	36.3	39358	32.8
Region of residence
Large cities	864284	32.9	38724	31.1	960205	33.8	41418	34.6
Southern Sweden	1104889	42.1	58902	47.4	1213259	42.8	55323	46.2
Northern Sweden	658191	25.1	26723	21.5	663417	23.4	23081	19.3
Marital status
Married	1576047	60.0	89548	72.0	2535098	89.4	107755	89.9
Not married	1051317	40.0	34801	28.0	301783	10.6	12067	10.1
Neighborhood deprivation
Low	366266	13.9	20069	16.1	392916	13.9	18558	15.5
Middle	1249190	47.5	64509	51.9	1390177	49.0	61238	51.1
High	296743	11.3	13660	11.0	329470	11.6	13270	11.1
Unknown	715165	27.2	26111	21.0	724318	25.5	26756	22.3
Hospital diagnoses:
Tinnitus	36126	1.4	21854	17.6	35658	1.3	17920	15.0
Intracranial trauma	70954	2.7	4986	4.0	63075	2.2	4075	3.4
Brain tumor	15322	0.6	2049	1.6	21491	0.8	2490	2.1
Stroke	257571	9.8	16311	13.1	252308	8.9	13408	11.2
Hypertension	477208	18.2	37544	30.2	524806	18.5	36384	30.4
CHD	352757	13.4	26508	21.3	250013	8.8	16496	13.8
COPD	150019	5.7	10169	8.2	190049	6.7	11492	9.6
Cancer (except brain tumors)	459133	17.5	33370	26.8	464865	16.4	27245	22.7
Diabetes	222195	8.5	14890	12.0	181279	6.4	10719	8.9
Arthropathy	481502	18.3	35438	28.5	620217	21.9	40378	33.7
Dementia	70809	2.7	4576	3.7	102585	3.6	5221	4.4
Depression	86003	3.3	5571	4.5	138001	4.9	7786	6.5
Visual impairment	6248	0.2	632	0.5	7880	0.3	725	0.6

CHD: Coronary heart disease; COPD: Chronic obstructive pulmonary disease.

Of the included 2 627 364 men, 2 193 544 were Swedish-born, of which 108 788 men had hearing impairment (mean age 64.1 years, SD 12.8). Among the 433 820 foreign-born men, 15 561 had hearing impairment (mean age 59.0 years, SD 13.0; S1a Table in S1 File). Among the women, 2 409 298 were Swedish-born, of which 105 260 had hearing impairment (mean age 65.7 years, SD 14.1), and 427 583 were foreign-born of which 14 562 had hearing impairment (mean age 60.7 years, SD 14.2; S1b Table in S1 File). The incidence rate was higher among foreign-born persons up to 60 years of age, and higher among Swedish-born individuals 60 years of age and above (data not shown). Of the included comorbid conditions, most were associated with a higher risk of hearing impairment (S2a and S2b Tables in S1 File). The most common comorbidities are shown in Table 1. Regarding sociodemographic factors, a higher educational level was associated with a slightly higher risk especially among foreign-born persons (S2a and S2b Tables in S1 File). Being married was also associated with a higher risk among men and among Swedish-born women, while neighborhood socioeconomic status showed no significantly different risk or was only marginally different (except for unknown level with a lower risk among Swedish-born men and women). Mean time to event was for men 14.2 years (SD 4.9) and women 14.5 years (SD 4.7); for Swedish-born men 14.3 years (SD 4.9) and foreign-born men 13.6 years (SD 5.3); and for Swedish-born women 14.5 years (SD 4.7) and foreign-born women 14.3 years (SD 4.8).

3.2 Differences between foreign-born and Swedish-born individuals

The results for foreign-born men and women compared to Swedish-born men and women (with the number of included individuals and cases in S3 Table in S1 File), respectively, are shown in Table 2, with slightly lower risks among foreign-born men but not among foreign-born women in the fully adjusted models. The risk was consistently higher in men and women from Asia, and also higher in models 2 and 3 in men and women from Eastern Europe, and women from Africa (Table 2). Results for specific countries (S4a and S4b Tables in S1 File) showed, for Asian countries, a consistently higher risk that was observed for both men and women from Turkey, Lebanon, Iran, and Iraq, and also, in models 2 and 3, in men and women from other Asian countries. For European countries, a consistently higher risk was found in men from Bosnia, and, in models 2 and 3, in women from Bosnia and former Yugoslavia. Lower risks were consistently found for men and women from all the Nordic countries (Denmark, Finland, Iceland, and Norway), and for most Southern European countries (i.e. for men from Greece, Italy and Spain, and women from France, Greece, and Italy), and also among men and women from UK and Ireland, and men from Hungary. In a sensitivity analysis, we also adjusted for time in Sweden (S5 Table in S1 File), with only minor differences from the earlier shown results, i.e. results were non-significant for men from Eastern Europe (HR 0.97, 99% CI 0.91–1.04), but significantly lower for men from Africa (HR 0.84, 99% CI 0.74–0.95) and Latin America (HR 0.87, 99% CI 0.87–0.99).

Table 2

Relative risk of hearing impairment in foreign-born men and women with Swedish-born men and women as referents, respectively, expressed as hazard ratios (HR) with 99% confidence intervals (99% CI).

		Model 1			Model 2			Model 3
	Obs.	HR	99% CI		HR	99% CI		HR	99% CI
Men
Sweden	108788	1			1			1
All foreign-born men	15 561	0.83	0.81	0.85	0.94	0.92	0.97	0.95	0.92	0.97
Nordic countries	4745	0.68	0.65	0.71	0.79	0.75	0.82	0.82	0.79	0.86
Southern Europe	637	0.53	0.47	0.59	0.64	0.57	0.72	0.68	0.60	0.76
Western Europe	1288	0.73	0.67	0.79	0.81	0.74	0.87	0.84	0.78	0.91
Eastern Europe	2204	1.01	0.95	1.07	1.14	1.07	1.21	1.08	1.01	1.15
Baltic countries	242	0.91	0.76	1.10	0.95	0.79	1.14	0.98	0.82	1.18
Central Europe	763	0.81	0.73	0.90	0.83	0.75	0.92	0.84	0.76	0.93
Africa	590	0.76	0.68	0.86	0.93	0.83	1.05	0.93	0.83	1.05
Northern America	224	0.58	0.48	0.70	0.69	0.57	0.83	0.76	0.63	0.92
Latin America	532	0.82	0.73	0.93	0.95	0.84	1.08	0.97	0.86	1.10
Asia	4169	1.26	1.20	1.31	1.45	1.39	1.52	1.33	1.27	1.39
Russia	111	0.74	0.57	0.97	0.85	0.65	1.11	0.86	0.66	1.13
Women
Sweden	105260	1			1			1
All foreign-born women	14 562	0.89	0.87	0.91	1.00	0.97	1.03	0.97	0.95	1.00
Nordic countries	6203	0.81	0.78	0.84	0.90	0.86	0.93	0.91	0.87	0.94
Southern Europe	311	0.48	0.40	0.56	0.58	0.49	0.68	0.62	0.52	0.72
Western Europe	1248	0.89	0.82	0.97	0.94	0.86	1.02	0.93	0.86	1.01
Eastern Europe	1488	0.95	0.88	1.02	1.13	1.05	1.22	1.13	1.05	1.22
Baltic countries	241	0.85	0.70	1.02	0.85	0.71	1.02	0.85	0.71	1.03
Central Europe	919	0.93	0.84	1.02	0.94	0.86	1.04	0.94	0.85	1.03
Africa	379	1.04	0.89	1.20	1.32	1.14	1.53	1.32	1.14	1.53
Northern America	172	0.58	0.47	0.72	0.67	0.54	0.83	0.68	0.55	0.85
Latin America	498	0.95	0.84	1.08	1.07	0.94	1.22	1.08	0.95	1.22
Asia	2874	1.27	1.20	1.34	1.55	1.47	1.64	1.53	1.44	1.62
Russia	177	0.84	0.68	1.04	0.96	0.77	1.19	0.96	0.78	1.19

Model 1: adjusted for age and region of residence in Sweden; model 2: adjusted for age, region of residence in Sweden, educational level, and marital status, and neighborhood deprivation; model 3: model 2 + comorbidities (tinnitus, intracranial trauma, malignant brain tumor, stroke, CHD, COPD, cancer, diabetes, arthropathies, dementia, depression, and visual impairment).

Bold values are statistically significant.

Categorization into different types of hearing impairment is shown in Table 3. Compared to Swedish-born individuals, the risk of conductive hearing impairment was higher in men and women from Eastern Europe, Africa and Asia, the risk of extended sensorineural hearing impairment was higher in men and women from Asia, the risk of noise-induced hearing impairment was higher in women from Eastern Europe (although the cases were few), and, finally, the risk of other types of hearing impairment was higher in men and women from Eastern Europe and Asia, and also in women from Africa and Russia.

Table 3

Relative risks of conductive hearing loss and other types of hearing loss in foreign-born men and women with Swedish-born men and women as referents, respectively, expressed as hazard ratios (HR) with 99% confidence intervals (99% CI)*.

	Conductive hearing impairment				Extended sensorineural hearing impairment				Noise-induced hearing impairment				Other hearing impairment
	Obs.	HR	99% CI		Obs.	HR	99% CI		Obs.	HR	99% CI		Obs.	HR	99% CI
Men
Sweden	4669	1			85335	1			3289	1			15495	1
Nordic countries	255	1.02	0.84	1.22	3617	0.81	0.77	0.85	156	0.94	0.74	1.19	717	0.86	0.77	0.96
Southern Europe	38	0.94	0.59	1.49	459	0.63	0.55	0.72	14	0.54	0.25	1.16	126	0.90	0.70	1.16
Western Europe	47	0.73	0.48	1.12	996	0.83	0.76	0.91	20	0.56	0.29	1.05	225	0.99	0.81	1.20
Eastern Europe	205	1.91	1.54	2.37	1494	0.95	0.88	1.03	74	1.29	0.92	1.82	431	1.46	1.27	1.68
Baltic countries	4	0.54	0.13	2.26	190	0.96	0.78	1.19	4	0.88	0.21	3.67	44	1.17	0.76	1.79
Central Europe	38	1.00	0.63	1.59	551	0.78	0.69	0.88	13	0.58	0.26	1.29	161	1.15	0.92	1.45
Africa	99	2.46	1.83	3.32	359	0.75	0.65	0.87	11	0.57	0.24	1.36	121	1.25	0.96	1.63
North America	7	0.50	0.17	1.47	164	0.72	0.57	0.89	10	1.44	0.58	3.57	43	0.98	0.63	1.51
Latin America	45	1.49	0.97	2.29	374	0.91	0.78	1.05	12	0.68	0.30	1.55	101	1.19	0.89	1.58
Asia	480	2.61	2.24	3.03	2795	1.17	1.11	1.24	103	0.99	0.73	1.33	791	1.75	1.56	1.95
Russia	4	0.67	0.16	2.78	78	0.77	0.56	1.07	2	0.70	0.09	5.22	27	1.43	0.83	2.48
Women
Sweden	6436	1			81018	1			332	1			17474	1
Nordic countries	415	1.01	0.87	1.17	4580	0.86	0.82	0.90	11	0.62	0.26	1.49	1197	1.02	0.93	1.11
Southern Europe	33	1.03	0.63	1.70	201	0.54	0.44	0.65	1	0.83	0.05	14.50	76	0.86	0.62	1.19
Western Europe	64	0.93	0.65	1.34	964	0.93	0.85	1.02	6	2.13	0.65	6.92	214	0.97	0.79	1.18
Eastern Europe	202	1.78	1.44	2.19	938	0.93	0.84	1.02	13	2.97	1.29	6.86	335	1.38	1.17	1.62
Baltic countries	10	0.88	0.36	2.17	191	0.85	0.69	1.05	0				40	0.87	0.55	1.36
Central Europe	87	1.31	0.96	1.78	642	0.82	0.73	0.92	3	0.96	0.18	5.03	187	1.02	0.83	1.26
Africa	78	2.41	1.73	3.36	201	0.93	0.76	1.14	1	0.83	0.05	14.55	99	1.76	1.32	2.36
North America	10	0.68	0.27	1.67	134	0.74	0.58	0.94	1	1.72	0.10	30.05	27	0.67	0.39	1.17
Latin America	58	1.42	0.97	2.07	330	0.91	0.78	1.07	5	2.60	0.71	9.48	105	1.16	0.87	1.53
Asia	473	2.40	2.07	2.78	1719	1.14	1.06	1.23	12	1.38	0.58	3.29	670	1.80	1.60	2.02
Russia	16	1.17	0.57	2.39	113	0.79	0.61	1.04	0				48	1.51	1.00	2.28

*: Fully adjusted.

Bold values are statistically significant.

3.3 Sensitivity analyses

We analyzed the number of all diagnoses of hearing impairments in men and women, respectively (S6a and S6b Tables in S1 File). The most common diagnoses were bilateral sensorineural hearing loss (ICD-10 code H90.3), which was found among men (38.9%) and among women (36.6%), and unspecified sensorineural hearing loss (ICD-10 code H90.5), among men 25.0% and among women 23.9%. Presbyacusis (H91.1) was registered only among 6.05 among men and 7.8% among women.

4. Discussion

The main results of this study were that the overall risk of hearing impairment among immigrant men in Sweden was somewhat lower than among Swedish-born men. This was, however, not the case among immigrant women. However, several immigrant subgroups showed a higher risk, especially men and women from Asia and women from Africa, and also, to a moderate extent, men and women from Eastern Europe. This was partly in-line with our hypothesis, i.e., that there is an increased risk of hearing impairment among certain immigrant groups to Sweden. For the different subgroups of hearing impairment, the pattern with a higher risk in immigrants from Eastern Europe, Africa and Asia seemed to be strongest for conductive hearing impairment.

The lower risk in many immigrant groups, i.e. those from North America and many European countries, except for immigrants from Eastern Europe, might to some extent represent a “healthy migrant effect”, meaning that migrating individuals tend to have particularly good health compared to individuals living in the same country of origin [16]. However, we have no detailed information to support this hypothesis, and an earlier Danish study recommended using this theory of “healthy migrant effect with caution” [17]. Another potential explanation for the lower rates may be that immigrants with poor health and hearing loss may move back, to a higher degree, to their home countries, than Swedish-born individuals with the same health problems, a phenomenon called salmon bias.

The increased risk for hearing impairment found in men and women from some regions, i.e. Asia, and in women from Africa, was found for both conductive hearing loss and other types of hearing impairment. These findings would need further studies of potential differences in risk factors between different ethnic groups, such as differences in genetic risk factors and relevant environmental exposures, e.g., noise. In an earlier study conducted by our group, we found than an increased risk in boys with parents from Asia could indicate that hereditary factors could be of importance [11]. The finding of an increased risk among men and women from Bosnia is also of interest. Regarding immigrants from Bosnia, they are refugees to a higher extent than other immigrants, as also immigrants from Iran and Iraq are [18], and this is also of interest to study further. However, the risk was also higher among men and women from Lebanon and Turkey. Our findings are also in contrast to earlier findings with lower risks of hearing impairment in Middle Eastern countries [19]. There may be a higher risk among refugees from war-torn countries where individuals may have been exposed to noise from gunfire and bombing. Untreated infections due to poorer health care in the country of origin, problems obtaining proper health care during the migration process, and differences in noise exposure in different countries may also explain the differences.

Regarding sex patterns, we found a slightly higher incidence for men compared to women, i.e. 4.7 vs 4.2%, which is in-line with findings in the rest of the world [2]. However, the excess risk among men was lower than that in other studies, e.g., as shown in an American study including adults aged ≥18 years of age that found a 60% higher risk of hearing loss among men than what was found in women [3]. We also found that being married was associated with a higher risk for hearing impairment among men. Married men could be more prone to seek health care and be diagnosed with a hearing impairment, as their medical problems could be noticed by their spouses. For example, we have previously noticed a lower risk of being diagnosed with dementia in unmarried and widowed men with atrial fibrillation in contrast to what could be expected, which could be interpreted that the disease is diagnosed at later stages [20]. Women have been found to seek health care more often than men [21].

Among socioeconomic factors, we found that a higher educational level was associated with a higher risk of hearing impairment, which is in contrast to an earlier American study [3]. One explanation behind these findings could be that health care seeking patterns might differ between different socioeconomic groups, where highly educated individuals may be more likely to seek care for their health problems than individuals with low education. However, a review of access to rehabilitation services, including hearing rehabilitation, concluded that no clear patterns could be seen as regards different factors including socioeconomic status, mostly owing to a lack of studies [22], although hearing loss is often underdiagnosed in the general population [23].

The co-morbidity patterns did not differ much between Swedish-born and foreign-born individuals, most likely owing to the fact that many of the foreign-born individuals are of European origin, with similar disease patterns as in Sweden. Tinnitus is of special interest, as it is highly associated with hearing impairment [24] and could be worthwhile to analyze separately. The higher risk of having both hearing and visual impairment, even if the excess risk was small, is also of special interest, i.e., the so-called dual-sensory impairment [4]. In individuals with the dual-sensory impairment, their health is even more affected [25] and also associated with a higher risk of early mortality [26, 27]. One study, which was conducted among individuals aged 55 years and older, found a higher risk of falls among individuals with dual-sensory impairment. However, that disappeared when also adjusting for cognitive impairment [28]. As regards falls, we included intracranial trauma as an indicator of more serious falls. Some other causes of hearing impairment, such as infections and ototoxicity from certain drugs, are difficult to capture in registers [29] and beyond the scope of the present study. In women, dementia was associated with a lower risk of hearing impairment. This might be due to hearing loss being underdiagnosed in individuals with dementia, due to difficulties in performing hearing tests and difficulties trying out, learning to use, and managing a hearing aid.

Identifying hearing impairment is important as correction with hearing aids and rehabilitative services, such as auditory and communication training, have been shown to increase well-being and quality of life [9], especially among immigrants, who otherwise will have even greater difficulties learning a new language.

There are some limitations of this study. We used data from the NPR, where cases of deafness are likely to be identified, whereas other degrees of hearing impairment could be missed. Systemic errors could be problematic when using registry databases, and it is difficult to check the accuracy of the diagnoses. In addition, since primary health care data were not used, it is possible that some individuals with hearing impairment could have been missed. The number of cases diagnosed as presbycusis was low, most likely to be underestimated. Furthermore, the number of cases of hearing loss was low in some immigrant groups, especially when categorized into subgroups of hearing impairment. The care seeking patterns could differ between different groups of immigrants and also between immigrants and Swedish-born individuals, which also could have affected our results. Other individual characteristics, that may differ between immigrant groups and Swedish-born individuals, such as trust in physicians and chronic conditions not included in our data registers, could have influenced our results [15].

Finally, we did not have access to more specific data on the levels of hearing impairment among the individuals in Sweden.

There are also certain strengths of the present study. For example, the overall quality of the Swedish registers is regarded to be high, both as regards the Total National Population Register [12], and the NPR [30]. Furthermore, as used in the present study, the Swedish personal identification number allows for linkages between different Swedish registers [13]. All data were analyzed using pseudonymized serial numbers to secure all individuals’ integrity.

In conclusion, we found an overall somewhat lower risk of hearing impairment in immigrant men but not in immigrant women. The findings of higher risks in some immigrant groups may need further attention because hearing loss may affect learning of the Swedish language and other aspects of successful integration. This suggests a need of an increased clinical awareness of potential hearing impairment when encountering patients belonging to certain immigrant groups.

(DOCX)

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14 Mar 2022

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Reviewer #1: Partly

Reviewer #2: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

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Reviewer #1: Yes

Reviewer #2: No

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Regarding the revision to the manuscript.

One concern is about using a measure of hearing impairment that is based on having a registered diagnosis. In the discussion you allude to the fact that there are not likely nativity differences in seeking behaviors, but there is no evidence or citation provided. Are the foreign born in Sweden less likely to have a routine source of care or to seek care when it is needed? How might language ability inform who receives a registered diagnosis?

Please clarify the timing of receiving a hearing impairment diagnosis in the text. After reading the paper, it is clear that the diagnosis happens in Sweden. Could immigrants who received a diagnosis, in their home country, prior to migrating be missed in the NPR? Is everyone in the NPR evaluated for a hearing impairment?

What is the substantive or analytic value at analyzing hearing impairments separately by types? You mention small number of cases for some types of hearing impairments, how small? In Table 2 are all hearing impairments combined together? When you refer to hearing impairment generally in the discussion when summarizing results, what type or types of impairments are included?

What if any are the limitations of not having patient diagnoses of hearing impairments from primary health care?

Did you try models with just 2001 data and beyond from outpatient diagnoses? Are there differences between hospital and outpatient diagnoses?

Is it possible to include other co morbidities such as physical limitations?

Do you have other immigration related measures?

Here I am specifically thinking about factors like duration of residence in Sweden or age at arrival in Sweden? Cohort of arrival?

In addition to education, can you control for their language ability?

Do you know the age at which they were diagnosed with a hearing impairment?

The inclusion of the neighborhood SES is not clear. It is not theorized about in the front end of the paper. What is the importance on including? The models are set up in a way to examine whether/how SES explains some of the country of birth and hearing impairment association but again this is not theorized in the front end.

The conclusion needs revisions/expansion. Specifically, why does understanding hearing impairment by nativity matter in Sweden? Expand on this conclusion point about hearing difficulty and learning a language. What are the implications for integration for themselves or their children? Or for policy?

Reviewer #2: Thank you for allowing me to review this paper. While this study was conducted rather comprehensively, there are several major concerns with the justification for the study and written methodology/analytic approach.

The justification to conduct this study needs to be expanded upon- why is it important to better understand differences in risk between foreign-born and Swedish-born adults? Please consider highlighting this earlier in the introduction and expanding on the decision to present only sex stratified results and the benefits for this approach. The discussion would also benefit from expanding on the implications of study findings for the target population.

The relevance of associations with comorbidities is unclear throughout the manuscript. How were these factors chosen (e.g., via existing literature and/or by evaluating confounding in the data; this needs to be expanded upon in introduction & methods and more citations are needed that are specific to hearing loss)? It is not clear why region is divided into urban, northern, and southern Sweden- does urbanicity vary across northern/southern Sweden? The NSES is built with both an education status variable and a geographical variable, although different measures of education and geography were already adjusted for. This introduces substantial concerns of collinearity of the covariates included in Models 2 and 3.

A strength of this study is that it uses longitudinal data to evaluate relative risk of hearing impairment. However, there is a lack of detail on the timeline of the study period which makes it difficult to interpret results. When were baseline characteristics measured, was it before Jan 1, 1998? Please provide more information of longitudinal follow up in this sample and how different times to the event were handled. How were patients treated that died or emigrated prior to the end of the study period? What was the average time to event?

Methods 2.1 states that codes were assigned when treated. Is this true, or were codes assigned when treated or diagnosed? The division of types of hearing loss (i.e., conductive, sensorineural, other) described in the methods section does not match how data are presented in Table 3. What does ‘other’ refer to in the methods?

What was the motivation for stratifying to categories conductive and ‘other’ (Table 3)? The ‘other’ category in Table 3 appears to include several types of hearing loss (i.e., sensorineural, mixed, ototoxic, other causes; this also needs to be labeled on the table) that would likely have different etiologies, and for which the risk would vary across foreign- and Swedish-born for several different reasons. The broad categorization of the ‘other’ category may also mask relevant associations. Is adjustment for the covariates in Model 3 relevant for these different types of hearing loss given their different etiologies?

The discussion highlights that risk of hearing impairment in foreign-born men is lower than Swedish-born men. Please highlight that the risk is low (HR = 0.97) and discuss why the overall HR is low (although HRs appear substantially different after further stratification).

The limitations section should mention systematic errors present in registry databases. For example, the methods states that codes are only available from specialists, not primary care – please discuss how that would impact study results. Hearing loss is often underdiagnosed despite it being present – please discuss how this limitation of using registry data impacts results. The strengths section states there are no anticipated differences in foreign and Swedish individuals in health care seeking because access is good. Access and health care seeking are different concepts and health care seeking can be motivated by several factors that are not related to only access. Please clarify. Please expand on factors that were potentially uncontrolled for in these analyses.

Lastly, there are numerous grammatical errors and incorrect word choices throughout the manuscript. It is recommended that authors carefully proofread the manuscript prior to resubmission.

Specific comments:

Introduction:

P1, sentence 2: please rephrase. Etiologies and risk should be 2 separate concepts.

P1, last sentence: what was the age range of the study reporting 6% hearing loss prevalence? That study is from 1992, there are numerous cohort studies with more recent data.

P5: unclear what ‘non-Western regions’ refers to. Most of the earlier text focuses on risk differences in Western Europe/United states vs Asian regions but the hypothesis states there will be anticipated differences also in Central/Eastern Europe. Please clarify.

There are several places where the word ‘cause’ is used in reference to comorbidities. Please reword. It is not biologically plausible that some of these comorbidities (e.g., visual impairment) cause hearing impairment.

Please avoid single-sentence paragraphs.

Results:

-Methods state that age is used continuously in models, but age is presented categorically in tables. Please also provide mean / SD / range of age in text.

-Please consider reorganizing the results section to include headers on the topic being presented. Please consider including %s rather than only numerators/denominators in the text and tables. In several sections of the results, it is unclear which table is being referred to (e.g., ‘incidence rate’ in >60 and <=60 yrs).

-Considering commenting on protective HR for dementia association in women.

-Please consider reformatting tables to make it clearer when subcategories exist (e.g., Table 2: could indent regions under ‘all foreign born’ categories). Authors may also consider creating a header for ‘hospital diagnosis of…’ then listing conditions underneath.

-Table 1: please consider statistically evaluating differences in baseline characteristics between men and women.

-Prevalence of visual impairment seems to be very low. Please discuss why and potential implications for interpretations of results given that hearing and visual impairment often co-occur in aging.

-Please provide more detailed footnotes on adjustment for tables (e.g., Table 3, Supplementary tables)

Discussion:

-authors compare results to a prevalence study [3] showing 60% higher odds (not risk) of hearing loss in men vs women. Cross-sectional results from that study, presented as OR, cannot be directly compared to these longitudinal study results, presented as HR.

-It is not clear how the male-female health-survival paradox fits with study findings – please clarify. Citations are needed for statements on sex and socioeconomic differences in health care seeking.

-what does ‘disease patterns’ refer to? Please clarify.

-why would healthy migrant effects only apply to immigrants from certain regions?

**********

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27 May 2022

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Our response: The ethics statement is now included in the Methods section.

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Thank you for selecting this journal for your manuscript submission. Your paper has received very thorough and constructive evaluations that indicate that it would require major revisions before being accepted for publication. Should you decide to submit a revised manuscript, please include a point-by-point response to the reviewers' concerns.

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

________________________________________

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

________________________________________

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

________________________________________

4. Is the manuscript presented in an intelligible fashion and written in standard English?

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Reviewer #2: Yes

________________________________________

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Regarding the revision to the manuscript.

One concern is about using a measure of hearing impairment that is based on having a registered diagnosis. In the discussion you allude to the fact that there are not likely nativity differences in seeking behaviors, but there is no evidence or citation provided. Are the foreign born in Sweden less likely to have a routine source of care or to seek care when it is needed? How might language ability inform who receives a registered diagnosis?

Our response: There are only a few studies regarding the context of equal care. The available studies have been undertaken on other patient groups with different diseases or diagnoses. In a study of second myocardial infarctions, low socioeconomic status was a risk factor for a less routine source of care, which remained after adjustments for immigrant status. Immigrants do not seem less likely to have a routine source of care. Language problems might of course affect the understanding of what a specific diagnosis means in practice and daily life, but we have not found studies to support that claim. If requested, we could delete that statement from the discussion section.

Please clarify the timing of receiving a hearing impairment diagnosis in the text. After reading the paper, it is clear that the diagnosis happens in Sweden. Could immigrants who received a diagnosis, in their home country, prior to migrating be missed in the NPR? Is everyone in the NPR evaluated for a hearing impairment?

Our response: Surely an immigrant could have received a diagnosis for hearing impairment in the country of origin. However, to get access to hearing aids, which are subsidized in Sweden, a visit to the Swedish healthcare system is needed, hence why we expect that the risk of being missed in the NPR should be small. Everyone will not be evaluated as the NPR is based upon a diagnosis after a clinical visit.

What is the substantive or analytic value at analyzing hearing impairments separately by types? You mention small number of cases for some types of hearing impairments, how small? In Table 2 are all hearing impairments combined together? When you refer to hearing impairment generally in the discussion when summarizing results, what type or types of impairments are included?

Our response: We have separated hearing impairments by types as the causes behind them may vary. We have now added the numbers of the specific diagnoses for men and women (see the new Supplementary Tables 6a and 6b).

What if any are the limitations of not having patient diagnoses of hearing impairments from primary health care?

Our response: Hearing impairment, although often suspected in primary care, should normally be diagnosed in secondary care, hence why we could expect that the limitations of not having primary care diagnoses should be limited.

Did you try models with just 2001 data and beyond from outpatient diagnoses? Are there differences between hospital and outpatient diagnoses?

Our response: We have not performed such analyses as we believed that the main question is that the diagnoses are captured, whether in inpatients or outpatients. However, if this is requested we are willing to conduct such analyses.

Is it possible to include other co morbidities such as physical limitations?

Our response: We included important diagnoses, such as stroke and arthropathy, in order to capture physical limitations. Otherwise, it may be difficult to catch other conditions leading to physical limitations as many of these conditions are cared for in primary care.

Do you have other immigration related measures?

Here I am specifically thinking about factors like duration of residence in Sweden or age at arrival in Sweden? Cohort of arrival?

Our response: We have now added a sensitivity analysis with adjustment for duration of residence in Sweden/time in Sweden (see the new Supplementary Table 5).

In addition to education, can you control for their language ability?

Our response: No, we have no data on this.

Do you know the age at which they were diagnosed with a hearing impairment?

Our response: Yes, we have the first event and age registered.

The inclusion of the neighborhood SES is not clear. It is not theorized about in the front end of the paper. What is the importance on including? The models are set up in a way to examine whether/how SES explains some of the country of birth and hearing impairment association but again this is not theorized in the front end.

Our response: Neighborhood SES has been shown to be an important socioeconomic factor for several health outcomes and we have added a sentence to justify its inclusion (inserted on p. 6).

The conclusion needs revisions/expansion. Specifically, why does understanding hearing impairment by nativity matter in Sweden? Expand on this conclusion point about hearing difficulty and learning a language. What are the implications for integration for themselves or their children? Or for policy?

Our response: For planning actions in the health care system and society, it is important to know patterns of hearing impairment in different immigrant groups. Furthermore, hearing impairment may affect integration in Sweden as it potentially will increase the language barriers.

Reviewer #2: Thank you for allowing me to review this paper. While this study was conducted rather comprehensively, there are several major concerns with the justification for the study and written methodology/analytic approach.

The justification to conduct this study needs to be expanded upon- why is it important to better understand differences in risk between foreign-born and Swedish-born adults? Please consider highlighting this earlier in the introduction and expanding on the decision to present only sex stratified results and the benefits for this approach. The discussion would also benefit from expanding on the implications of study findings for the target population.

Our response: To know patterns of hearing impairment in different immigrant groups is of importance for both the health care system and to society in general; this is for planning actions and to identify hearing impairment early on after migration in order to Sweden to give immigrants the best possible opportunity to learn Swedish and to get integrated in Sweden. Investigating potential differences by sex is also important as men and women have different life circumstances worldwide.

The relevance of associations with comorbidities is unclear throughout the manuscript. How were these factors chosen (e.g., via existing literature and/or by evaluating confounding in the data; this needs to be expanded upon in introduction & methods and more citations are needed that are specific to hearing loss)? It is not clear why region is divided into urban, northern, and southern Sweden- does urbanicity vary across northern/southern Sweden? The NSES is built with both an education status variable and a geographical variable, although different measures of education and geography were already adjusted for. This introduces substantial concerns of collinearity of the covariates included in Models 2 and 3.

Our response: We included the selected comorbidities as several of them are related to physical limitations which often are seen together with hearing impairment. The rough geographical pattern was chosen to adjust for possible differences in health care between the more densely populated areas in the larger cities and southern Sweden, and the less densely populated areas in northern Sweden. The neighborhood SES includes different factors, where low educational status is only one. It is true that there is some overlapping between the different covariates. However, we don’t entirely agree that large problems with collinearity exist as the different SES factors reflect different assessments at different levels. We have previously shown, for example, that neighborhood SES is a risk factor for appropriate prescribed medications, stroke and myocardial infarction that is independent of individual education level and migration status.

A strength of this study is that it uses longitudinal data to evaluate relative risk of hearing impairment. However, there is a lack of detail on the timeline of the study period which makes it difficult to interpret results. When were baseline characteristics measured, was it before Jan 1, 1998? Please provide more information of longitudinal follow up in this sample and how different times to the event were handled. How were patients treated that died or emigrated prior to the end of the study period? What was the average time to event?

Our response: We used an open cohort design and as Cox regression was used in the statistical analysis, only the first event was registered. Risk time was calculated until the event and those who died or emigrated were censored (these sentences are now included on pp. 6-7). We have now clarified this in the methods section. We have now also included mean time to event (Results, p. 8).

Methods 2.1 states that codes were assigned when treated. Is this true, or were codes assigned when treated or diagnosed? The division of types of hearing loss (i.e., conductive, sensorineural, other) described in the methods section does not match how data are presented in Table 3. What does ‘other’ refer to in the methods?

Our response: The codes refer to clinical diagnoses and the codes were given on the first occasion. We chose to stratify into the categories “Conductive and sensorineural hearing loss” and “Other hearing loss”, and have clarified this in the methods. Thus, the texts in Methods and Table 3 are now congruent. We have included the specific diagnoses and codes in supplementary Table 6a. Data on treatment are not included in the present manuscript.

What was the motivation for stratifying to categories conductive and ‘other’ (Table 3)? The ‘other’ category in Table 3 appears to include several types of hearing loss (i.e., sensorineural, mixed, ototoxic, other causes; this also needs to be labeled on the table) that would likely have different etiologies, and for which the risk would vary across foreign- and Swedish-born for several different reasons. The broad categorization of the ‘other’ category may also mask relevant associations. Is adjustment for the covariates in Model 3 relevant for these different types of hearing loss given their different etiologies?

Our response: We chose to stratify into the categories “Conductive and sensorineural hearing loss” and “Other hearing loss”, and have clarified this in the methods. Thus, the texts in Methods and Table 3 are now congruent. We have included all diagnoses in Supplementary Table 6a. We agree that the choice of covariates could be questioned, but the adjustment for co-morbidities only changed the HRs marginally.

The discussion highlights that risk of hearing impairment in foreign-born men is lower than Swedish-born men. Please highlight that the risk is low (HR = 0.97) and discuss why the overall HR is low (although HRs appear substantially different after further stratification).

Our response: We have extended the discussion; several groups showed a lower risk, i.e. men and women from the Nordic countries, Southern Europe, and North America. Individuals from the Nordic countries constitute a large group in Sweden, and the lower risk in the mentioned groups explains why the risk is somewhat lower overall. In addition, there is the possibility of healthy migrant effects, i.e. that individuals with poorer health, including hearing impairment, are less likely to migrate.

The limitations section should mention systematic errors present in registry databases. For example, the methods states that codes are only available from specialists, not primary care – please discuss how that would impact study results. Hearing loss is often underdiagnosed despite it being present – please discuss how this limitation of using registry data impacts results. The strengths section states there are no anticipated differences in foreign and Swedish individuals in health care seeking because access is good. Access and health care seeking are different concepts and health care seeking can be motivated by several factors that are not related to only access. Please clarify. Please expand on factors that were potentially uncontrolled for in these analyses.

Our response: We have extended the discussion, accordingly.

Lastly, there are numerous grammatical errors and incorrect word choices throughout the manuscript. It is recommended that authors carefully proofread the manuscript prior to resubmission.

Our response: The manuscript has now been proofread by a native English-speaking science editor.

Specific comments:

Introduction:

P1, sentence 2: please rephrase. Etiologies and risk should be 2 separate concepts.

Our response: We have now reworded the sentence and divided it into two sentences.

P1, last sentence: what was the age range of the study reporting 6% hearing loss prevalence? That study is from 1992, there are numerous cohort studies with more recent data.

Our response: Reference article 3 by Li et al was published in 2018, and describes two surveys from 2014 and 2016, respectively, and the sub-studies include individuals 18 years of age and above. The article from 1992 was authored by Winkleby et al concerning socioeconomic status.

P5: unclear what ‘non-Western regions’ refers to. Most of the earlier text focuses on risk differences in Western Europe/United states vs Asian regions but the hypothesis states there will be anticipated differences also in Central/Eastern Europe. Please clarify.

Our response: We agree that the wording of “Western” and “non-Western” regions is often vague and have omitted these categories in the manuscript.

There are several places where the word ‘cause’ is used in reference to comorbidities. Please reword. It is not biologically plausible that some of these comorbidities (e.g., visual impairment) cause hearing impairment.

Our response: We agree and have changed the wording as suggested.

Please avoid single-sentence paragraphs.

Our response: We have avoided this now.

Results:

-Methods state that age is used continuously in models, but age is presented categorically in tables. Please also provide mean / SD / range of age in text.

Our response: We have now added mean age + SD in the text.

-Please consider reorganizing the results section to include headers on the topic being presented.

Our response: We have now included headers.

Please consider including %s rather than only numerators/denominators in the text and tables. In several sections of the results, it is unclear which table is being referred to (e.g., ‘incidence rate’ in >60 and <=60 yrs).

Our response: We have now tried to specify better which tables are being referred to. We prefer to keep both numbers and percentages in Table 1 and the Supplementary Tables 1a and 1b, but could change this if it is requested.

-Considering commenting on protective HR for dementia association in women.

Our response: We have now added a sentence on this.

Discussion, p. 12: “In women, dementia was associated with a lower risk of hearing impairment. This might be due to hearing loss being underdiagnosed in individuals with dementia, due to difficulties in performing hearing tests and difficulties trying out, learning to use, and managing a hearing aid.”

-Please consider reformatting tables to make it clearer when subcategories exist (e.g., Table 2: could indent regions under ‘all foreign born’ categories). Authors may also consider creating a header for ‘hospital diagnosis of…’ then listing conditions underneath.

-Table 1: please consider statistically evaluating differences in baseline characteristics between men and women.

Our response: We have changed the comorbidity sections in Table 2 and included “hospital diagnosis” as a header. Regarding the differences between men and women in general we prefer not to evaluate the differences, as the main theme is difference between foreign-born and Swedish-born individuals. We do believe that the difference in percentages between men and women could easily be found for the interested reader.

-Prevalence of visual impairment seems to be very low. Please discuss why and potential implications for interpretations of results given that hearing and visual impairment often co-occur in aging.

Our response: We have no confident explanation for this. One possible explanation is that low or moderate degrees of visual impairment among elderly individuals are not noticed and registered.

-Please provide more detailed footnotes on adjustment for tables (e.g., Table 3, Supplementary tables)

Our response: We have done so.

Discussion:

-authors compare results to a prevalence study [3] showing 60% higher odds (not risk) of hearing loss in men vs women. Cross-sectional results from that study, presented as OR, cannot be directly compared to these longitudinal study results, presented as HR.

Our response: The results in that study present weighted prevalence and adjusted prevalence rates (PRs), hence why we think that the wording is correct. We have, however, added a sentence that these results may not be directly comparable with ours.

-It is not clear how the male-female health-survival paradox fits with study findings – please clarify.

Our response: This has mostly been discussed in relation to heart diseases, and we agree that it is difficult to discuss this term here, hence why we have omitted it.

Citations are needed for statements on sex and socioeconomic differences in health care seeking.

Our response: We have included a systematic review on access to rehabilitation services, where the conclusion is that “no clear patterns were seen in access by equity measures such as age, locality, socioeconomic status, or country income group”, which is due to a low number of studies. Seeking patterns could be more complex, however, and it is difficult to generalize. In some studies, we have previously found some results that could be because some factors could be associated with earlier care seeking behaviors, mostly for married people whereas unmarried individuals without a partner seem to react later, e.g. for dementia or heart failure. However, we have no data supporting this on hearing impairment.

-what does ‘disease patterns’ refer to? Please clarify.

Our response: We agree that this is vaguely expressed and have changed the wording accordingly.

-why would healthy migrant effects only apply to immigrants from certain regions?

Our response: As regards to the healthy migrant effect there is no detailed information on this for different groups; an earlier Danish study recommended to use this theory with caution. However, in some of the immigrant groups with lower risk than among Swedish-born individuals, we could have expected a similar rather than a lower risk and this could be related to a healthy migrant effect.

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Reviewer #2: No

1 Jul 2022

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Additional Editor Comments:

Further revision is required before the manuscript can be considered for publication. The authors should revise the manuscript in response to the comments from Reviewer #2.

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Comments to the Author

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Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

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Reviewer #1: Yes

Reviewer #2: Partly

**********

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Reviewer #1: Yes

Reviewer #2: Yes

**********

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Reviewer #1: (No Response)

Reviewer #2: No

**********

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: Thank you for allowing me to review the revised draft of this paper. Below are comments based on these revisions. There are several points that remain unaddressed in the paper. The most important remaining concern is how hearing loss is classified and presented in Table 3.

Previous comment: The justification to conduct this study needs to be expanded upon- why is it important to better understand differences in risk between foreign-born and Swedish-born adults? Please consider highlighting this earlier in the introduction and expanding on the decision to present only sex stratified results and the benefits for this approach. The discussion would also benefit from expanding on the implications of study findings for the target population. ****Authors chose not to modify the text although these minor revisions may be helpful to the reader. Please reconsider.

Previous comment: The relevance of associations with comorbidities is unclear throughout the manuscript. How were these factors chosen (e.g., via existing literature and/or by evaluating confounding in the data; this needs to be expanded upon in introduction & methods and more citations are needed that are specific to hearing loss)? It is not clear why region is divided into urban, northern, and southern Sweden- does urbanicity vary across northern/southern Sweden? ****Authors chose not to modify the text although these minor revisions may be helpful to the reader. Please reconsider.

There remains a substantial issue (highlighted in previous comments) regarding how hearing loss is classified in Table 3. It is not clear why sensorineural hearing loss and conductive hearing loss are grouped together. Furthermore, diagnoses that present as sensorineural hearing loss (e.g., presbycusis, most types of ototoxic hearing loss) are misclassified in the ‘other’ category. Again, sensorineural and conductive hearing losses often have drastically different etiologies and there are regional differences in these etiologies. For example, permanent conductive hearing loss could more likely be influenced by differences in health care across countries (e.g., untreated ear infections) and is more highly prevalent in countries with lower income. Permanent sensorineural hearing loss is more likely due to aging/related processes and environmental and health-related risk factors. Again, there are different distributions of relevant exposures/risk factors across different regions/countries. I would strongly urge authors to re consider how these groups are defined. The line added to the discussion about presbycusis being underdiagnosed may not be true, as presbycusis may instead be diagnosed as sensorineural hearing loss. It is known that hearing loss, in general, is often underdiagnosed given patients’ underreporting of hearing difficulties and because many providers do not prioritize detection of hearing loss or appropriate referrals until hearing loss is more severe. This point, mentioned previously, also remains unaddressed in this revision.

Previous comment: The limitations section should mention systematic errors present in registry databases. For example, the methods states that codes are only available from specialists, not primary care – please discuss how that would impact study results. Hearing loss is often underdiagnosed despite it being present – please discuss how this limitation of using registry data impacts results. The strengths section states there are no anticipated differences in foreign and Swedish individuals in health care seeking because access is good. Access and health care seeking are different concepts and health care seeking can be motivated by several factors that are not related to only access. Please clarify. Please expand on factors that were potentially uncontrolled for in these analyses. ****Most of these points remain unaddressed. Please reconsider.

Previous comment: P1, last sentence: what was the age range of the study reporting 6% hearing loss prevalence? ****Information on the age range used to determine prevalence should be included in the text. Please reconsider.

Previous comment: In several sections of the results, it is unclear which table is being referred to (e.g., ‘incidence rate’ in >60 and <=60 yrs). ****No changes to address this are seen in the manuscript. Please reconsider.

Previous comment: what does ‘disease patterns’ refer to? Please clarify. ****Authors say the wording has been changed but it remains in the manuscript. Please reconsider.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

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4 Aug 2022

Additional Editor Comments:

Further revision is required before the manuscript can be considered for publication. The authors should revise the manuscript in response to the comments from Reviewer #2.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

________________________________________

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

________________________________________

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

________________________________________

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: No

________________________________________

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

________________________________________

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Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: Thank you for allowing me to review the revised draft of this paper. Below are comments based on these revisions. There are several points that remain unaddressed in the paper. The most important remaining concern is how hearing loss is classified and presented in Table 3.

Previous comment: The justification to conduct this study needs to be expanded upon- why is it important to better understand differences in risk between foreign-born and Swedish-born adults? Please consider highlighting this earlier in the introduction and expanding on the decision to present only sex stratified results and the benefits for this approach. The discussion would also benefit from expanding on the implications of study findings for the target population. ****Authors chose not to modify the text although these minor revisions may be helpful to the reader. Please reconsider.

Our response: Thank you for mentioning these issues again. We have now expanded on the justification to conduct this study. The acculturation (e.g., learning the new language) into the new homeland for foreign-born citizens is certainly depending on good hearing. Hearing impairment is therefore an important issue to study in order to provide help with correction, if possible. We have revised the following part of the introduction:

Introduction, p. 3: “As regards immigrants, hearing impairment may be challenging when learning the language and culture of a new country, which calls for attention and motivated us to conduct this study. Identifying hearing impairment is also important as correction with hearing aids and rehabilitative services have been shown to increase well-being and quality of life.”

We have also added the following new text in the methods section to justify the stratification by sex:

“The analyses were stratified by sex because men and women experience different types of environments, including those related to occupation, and also have different health care-seeking patterns. https://bmcprimcare.biomedcentral.com/articles/10.1186/s12875-016-0440-0”

Please also note that there were differences in the results based on sex. The discussion mentions these findings in the first two sentences.

The following new sentence has also been added as a last sentence to the discussion section in order to better reflect the implications of the study:

“This suggests a need of an increased clinical awareness of potential hearing impairment when encountering patients belonging to certain immigrant groups.”

In addition, the following text can be found in the discussion section, just before the limitations:

“Identifying hearing impairment is important as correction with hearing aids and rehabilitative services, such as auditory and communication training, have been shown to increase well-being and quality of life [9], especially among immigrants, who otherwise will have even greater difficulties learning a new language.”

Previous comment: The relevance of associations with comorbidities is unclear throughout the manuscript. How were these factors chosen (e.g., via existing literature and/or by evaluating confounding in the data; this needs to be expanded upon in introduction & methods and more citations are needed that are specific to hearing loss)? It is not clear why region is divided into urban, northern, and southern Sweden- does urbanicity vary across northern/southern Sweden? ****Authors chose not to modify the text although these minor revisions may be helpful to the reader. Please reconsider.

Our response: The chosen co-morbidities were based on existing literature and we have now added this information, together with references, in the methods section. Regarding regions in Sweden, we have added the following new text in the methods section:

“Regarding regions in Sweden, the urbanicity differs with many sparsely populated parts in northern Sweden with, in many cases, long transportation routes and also poorer access to ophthalmologists.”

There remains a substantial issue (highlighted in previous comments) regarding how hearing loss is classified in Table 3. It is not clear why sensorineural hearing loss and conductive hearing loss are grouped together. Furthermore, diagnoses that present as sensorineural hearing loss (e.g., presbycusis, most types of ototoxic hearing loss) are misclassified in the ‘other’ category. Again, sensorineural and conductive hearing losses often have drastically different etiologies and there are regional differences in these etiologies. For example, permanent conductive hearing loss could more likely be influenced by differences in health care across countries (e.g., untreated ear infections) and is more highly prevalent in countries with lower income. Permanent sensorineural hearing loss is more likely due to aging/related processes and environmental and health-related risk factors. Again, there are different distributions of relevant exposures/risk factors across different regions/countries. I would strongly urge authors to re consider how these groups are defined. The line added to the discussion about presbycusis being underdiagnosed may not be true, as presbycusis may instead be diagnosed as sensorineural hearing loss. It is known that hearing loss, in general, is often underdiagnosed given patients’ underreporting of hearing difficulties and because many providers do not prioritize detection of hearing loss or appropriate referrals until hearing loss is more severe. This point, mentioned previously, also remains unaddressed in this revision.

Our response: We agree with this comment and have now performed a new categorization of the diagnoses of hearing impairment, accordingly; we believe that the new classification is more accurate than the earlier, and the new results are shown in the new Table 3. In addition, we added the following new text to the last sentence in the fifth paragraph of the discussion:

“…although hearing loss is often underdiagnosed in the general population https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2769843.”

Previous comment: The limitations section should mention systematic errors present in registry databases. For example, the methods states that codes are only available from specialists, not primary care – please discuss how that would impact study results. Hearing loss is often underdiagnosed despite it being present – please discuss how this limitation of using registry data impacts results. The strengths section states there are no anticipated differences in foreign and Swedish individuals in health care seeking because access is good. Access and health care seeking are different concepts and health care seeking can be motivated by several factors that are not related to only access. Please clarify. Please expand on factors that were potentially uncontrolled for in these analyses. ****Most of these points remain unaddressed. Please reconsider.

Our response: We agree that the mentioned factors are important to be expanded in the limitations section and have done so:

Discussion, p. 13:

“Systemic errors could be problematic when using registry databases, and it is difficult to check the accuracy of the diagnoses. In addition, since primary health care data were not used, it is possible that some individuals with hearing impairment could have been missed.”

“The care seeking patterns could differ between different groups of immigrants and also between immigrants and Swedish-born individuals, which also could have affected our results. Other individual characteristics, that may differ between immigrant groups and Swedish-born individuals, such as trust in physicians and chronic conditions not included in our data registers, could have influenced our results (https://bmcprimcare.biomedcentral.com/articles/10.1186/s12875-016-0440-0).”

We have deleted the sentence that states that we do not expect any major differences in health care seeking patterns between immigrants and Swedish-born individuals.

Previous comment: P1, last sentence: what was the age range of the study reporting 6% hearing loss prevalence? ****Information on the age range used to determine prevalence should be included in the text. Please reconsider.

Our response: The age range in the US article by Li et al was adults aged ≥ 18 years. This is now mentioned in the text.

Previous comment: In several sections of the results, it is unclear which table is being referred to (e.g., ‘incidence rate’ in >60 and <=60 yrs). ****No changes to address this are seen in the manuscript. Please reconsider.

Our response: We apologize for being unclear. We have now added the text “data not shown” in parenthesis for the specific example. As we already have several Supplementary Tables, we did not include the specific results from this example. We also added information on which table(s) we refer to in other locations in the results section.

Previous comment: what does ‘disease patterns’ refer to? Please clarify. ****Authors say the wording has been changed but it remains in the manuscript. Please reconsider.

Our response: We agree and have changed the wording to “co-morbidity patterns” in the beginning of that sentence:

“The co-morbidity patterns did not differ much between Swedish-born and foreign-born individuals, most likely owing to the fact that many of the foreign-born individuals are of European origin, with similar disease patterns as in Sweden.”

________________________________________

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #2: No

________________________________________

9 Aug 2022

Hearing impairment among adult foreign-born and Swedish-born individuals: a national Swedish study

PONE-D-22-03415R2

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11 Aug 2022

PONE-D-22-03415R2

Hearing impairment among adult foreign-born and Swedish-born individuals: a national Swedish study

Dear Dr. Carlsson:

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