The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults.

BACKGROUND: Health is one of the most important factors that affect happiness. This study aimed to assess the association between happiness and self-rated health among the Iranian adult population.
METHODS: This cross-sectional study was conducted on a sample of adults aged 18-65 In Iran in 2020. Demographic information, the Oxford Happiness Questionnaire, and a single item on self-rated health were used to collect the data. The relationship between happiness with demographic variables and self-rated health was examined by performing logistic regression analyses.
RESULTS: In all, 19499 were studied (9845 males and 9654 females). The mean age of participants was 36.38± 8.17 years. The mean happiness score was 4.1± 0.57 (out of 6) and this for self-rated health was 3.66±1.2 (out of 5). The results obtained from logistic regression analysis showed that very poor health status (OR: 5.114, 95% CI, P = 4.490-5.824, p <0.001), poor or very poor income status (OR: 1.553, 95% CI, P = 1.406-1.716, p <0.001), unemployment (OR: 1.704, 95% CI, P = 1.432-2.029, p <0.001), being aged 25-34 years (OR: 1.190, 95% CI, P = 1.088-1.302, p <0.001), and years of education (OR for 10-12 years of education: 1.271, 95% CI = 1.174-1.377, p< 0.001) were significant contributing factors to a lower happiness.
CONCLUSION: The results showed that self-rated health was the most significant factor that affected happiness even after adjustment for socioeconomic variables, including age, income, employment, and education. Indeed, improving population health might be an effective measure to improve happiness among Iranians.

Introduction

The World Health Organization emphasizes that happiness is an essential factor in the concept of health [1,2] and is one of the main components of life satisfaction [3]. People who consider themselves happy have better physical health than people who think themselves unhappy [4]. Veenhoven defines happiness as ‘the degree to which an individual judges the overall quality of his or her life-as-a-whole favorably’; in other words, ‘how much one likes the life one lives’ [5].

According to the world happiness report (2017–2019), the highest and lowest happiness scores were for Finland and Afghanistan, respectively. The Islamic Republic of Iran ranked 118th among 153countries. Although happiness score in Iran was lower than some countries in the Eastern Mediterranean Region (EMRO), such as Saudi Arabia, Pakistan, Morocco, but was higher than some other countries including Jordan, Tunisia, and Egypt [6].

One of the most frequently used measures of self-reported health status is a single question asking individuals to rate their overall health on a scale from excellent to very poor. There is widespread agreement that this simple global question provides a useful summary of how individuals perceive their overall health status [7]. The results of a cross-national study that compared health in Egypt, Iran, Jordan, and the United States showed that means and standard deviations of self-rated health by country was (2.79±0.85), (2.99±0.81), (3.06±0.83), and (3.23±0.78), respectively [8].

The association between happiness and health or association between happiness and some health-related behaviors are well documented. For instance, a review on subjective well-being (popularly referred to as happiness or life satisfaction) reported that higher subjective well-being was associated with good health and longevity, better social relationships, work performance, and creativity [9]. Also, a recent study from 15 European countries reported that compared to inactive people, there was a positive dose-response association between physical activity volume and happiness [10]. A review including longitudinal and experimental studies, have found strong associations between happiness and health outcomes [11] such as death, coronary heart disease (CHD) [12,13], stroke [14], type 2 diabetes [15] and life expectancy [16]. As such, it is argued that impaired happiness might be a consequence of ill-health but also could potentially contributor to the risk of several diseases since happiness includes affective well-being (feelings of joy and pleasure), eudemonic well-being (sense of meaning and purpose in life), and evaluative well-being (life satisfaction) [17].

Although an association between health status and happiness depends on how health is measured [18], a study showed that the relationship between happiness and self-rated health is somewhat more robust than the correlations between happiness and medical examinations [19]. Self-rated health is a widespread health measure that is based on personal perception of one’s about their own health. It is a reliable measure, especially when objective data are insufficient to reflect disease severity or in patients with the undiagnosed disease [20].

Although there are several many Iranian studies on happiness [21], it seems that the relationship between happiness and health is overlooked. There is no national study in Iran, unlike other countries [22-26]. Thus to fill the gap, this national study aimed to investigate the relationship between happiness and health in Iran to contribute public health, health policy, and the existing knowledge on the topic.

Materials and methods

Design and participants

This was a national cross-sectional study conducted from 10 January to 20 January 2020 throughout all provinces in Iran. Currently Iran has 32 provinces with over 80 million populations. The inclusion criteria were aged 18–65, Iranian nationality, able to respond to the study questionnaires. No other restrictions were implemented.

Sample size and sampling

The following formula was used to estimate the sample size:

To estimate the sample size, according to a national study [27], and based on population density, the country was classified into five categories. Then, samples were selected based on multi-stage sampling from each category. In doing so, one province was randomly selected from each category. Then two cities and two rural settings were randomly selected in each province. Every household within the city and rural areas had the same probability of being sampled. The households to be sampled were selected using systematic sampling within each census section. Finally, sampling units (the individuals) were selected randomly from all eligible persons living in the same household. Informed consent was obtained from each individual after the purpose of the study was explained. Considering the effect size of 1.4, the sample size of 20320 was estimated. However, in practice, 19499 Iranian adults were entered into the study.

Measures

1. The Oxford standard Happiness Questionnaire (OHQ): The overall happiness score could be derived from some of the items scores divided by 29, giving a score range from 1 to 6(strongly disagree = 1, moderately disagree = 2, slightly disagree = 3, slightly agree = 4, moderately agree = 5, strongly agree = 6). The scores are interpreted as follows: Unhappy (1 to <2); moderately unhappy (2 to < 3); not very happy/unhappy (3 to <4); somewhat happy/moderately happy (4); rather happy/pretty happy (4 to <5); very happy (5 to <6); too happy (6) [28]. Psychometric properties of the Iranian version of questionnaire are well documented. Cronbach’s alpha coefficient (measure of internal consistency) and interclass correlation coefficient (measure of stability) were 0.90 and 0.79, respectively. The convergent and divergent validity of the questionnaire were high and acceptable [29].

2. Self-rated health: Self-rated health was assessed by a single item asking people to rate their general health status at present. Respondents self-rated their health status on a 5-point Likert scale as follows: very poor = 1, poor = 2, fair = 3, good = 4, very good = 5. The validity of self-rated health measures has been proven in several studies [30-32]. Validity and reliability of self-rated health measure among Iranian showed acceptable results. The criterion validity showed that the self-rated health and the WHO-5 well-being had positive correlation as expected (r = 0.5, p< 0.001). Additionally, the reliability of the self-rated health, using interclass correlation coefficient (ICC), was found to be 0.83; 95% CI (0.72 to 0.90) [32].

Statistical analysis

Data were explored using descriptive statistics, including frequency, percentage, mean and standard deviation. The missing data were replaced with each item series mean. Logistic regression analyses were performed to assess the relationship between happiness and independent variables, including participants’ health status. However, since some eminent scholars [33] believe that there is an auto-correlation between item 28 and the self-rated health, we did calculate, and reanalyze the data while item 28 (I do not feel particularly healthy) was excluded from the Oxford happiness score. As such for both with and without item 28 of the Oxford questionnaire, happiness as dependent variables were categorized into: ‘happy’ (scores ranging from 4 to 6) and ‘unhappy’ (scores ranging from 1 to 3). The results expressed as odds ratio and 95% confidence intervals. A significant level was set at P< 0.05. Since this questionnaire covers broader matters than happiness [33], we calculated correlations for the few items on life satisfaction with self-rated health separately.

Ethics statement

The National Institutes for Medical Research Development (NIMAD), Tehran, Iran. ethics committee approved the study (IR.NIMAD.REC.l398.228). Due to the study design and all participants gave their verbal consent.

Results

A total of 19499 Iranian adults participated in the study (9845 males and 9654 females). The mean age of participants was 36.38 ± 8.17 years and the mean years of education were 10.51±4.43. Demographic details of the participants are presented in Table 1.

Table 1

Frequency distributions of the participants’ demographic characteristics.

	Female (n = 9845)	Male) n = 9654)	Total) n = 19499)
	No. (%)	No. (%)	No. (%)
Age(year)
18–24	982(10.0)	278(2.9)	1260(6.5)
25–34	3914(39.8)	3190(33.0)	7104(36.4)
35–44	3614(36.7)	3846(39.8)	7460(38.3)
45–65	1335(13.6)	2340(24.2)	3675(18.8)
Education (year)
1–5	2062(20.9)	1353(14.0)	3415(17.5)
6–9	2163(22.0)	2211(22.9)	4374(22.4)
10–12	3304(33.6)	3109(32.2)	6413(32.9)
13≤	2316(23.5)	2981(30.9)	5297(27.2)
Employment status
Employed	1150(11.7)	8478(87.8)	9628(49.4)
Housewife	8470(86.0)	0(0.0)	8470(43.4)
Retired	39(0.4)	389(4.0)	428 (2.2)
Student	180(1.8)	151(1.6)	331(1.7)
Unemployed	6(0.1)	636(6.6)	642(3.3)
Income (self-reported)
Very good/ good	2323(23.6)	2007(20.8)	4330(22.2)
Intermediate	5962(60.6)	5862(60.7)	11824(60.6)
Very poor/poor	1560(15.8)	1785(18.5)	3345(17.2)

The results showed that the mean happiness score was 4.1 ± 0.57 (out of 6), and this was 3.66±1.2 (out of 5) for self-rated health. Overall, 51.6% of the respondents scored more than four and less than 5, indicating a rather happy/pretty happy condition (4> to <5). The findings also showed that 34.8% of the participants reported their health status as very good, and %6.9 reported their health status as very poor. The detailed results are shown in Table 2. In addition, the results obtained from correlation between few items on life satisfaction and self-rated health in are presented in Table 3. Overall the findings showed a relatively low correlation (r = 0.15).

Table 2

Overall distribution of Oxford happiness scores and self-rated health scores (n = 19499).

	Frequency	Percent
Happiness (score range)
Unhappy (1 to < 2)	11	0.1
Moderately unhappy (2 to < 3)	474	2.4
Not very happy/unhappy (3 to <4)	7600	39.0
Somewhat happy/moderately happy (4)	329	1.7
Rather happy/pretty happy (4> to <5)	10059	51.6
Very happy (5 to <6)	1022	5.2
Too happy (6)	4	0.0
Mean (SD)	4.10 (0.57)
Happiness without item 28
Mean (SD)	4.09 (0.57)
Self-rated health
Very poor	1348	6.9
Poor	2349	12.0
Fair	4494	23.0
Good	4530	23.2
Very good	6778	34.8
Mean (SD)	3.66 (1.2)	-

Table 3

Correlation between the oxford happiness questionnaire few items on life satisfaction and self-rated health.

	Correlation coefficient
I don’t feel particularly pleased with the way I am(R)	0.08
I feel that life is very rewarding	0.12
Life is good	0.13
I do not think that the world is a good place (R)	0.11
I am well satisfied about everything in my life	0.11
Total	0.15

The results obtained from logistic regression analysis showed that people with very poor health status (OR: 5.114, 95% CI, P = 4.490–5.824, p <0.001), people with poor or very poor income level (OR: 1.553, 95% CI, P = 1.406–1.716, p <0.001), unemployed (OR: 1.704, 95% CI, P = 1.432–2.029, p <0.001), aged (OR: 1.190, 95% CI, P = 1.088–1.302, p <0.001), and people with 10–12 years of education (OR:1.271, 95% CI, P = 1.174–1.377, p <0.001) were more likely to report a lower score for happiness. The results are shown in Table 4. In addition, the results obtained from the same analysis when items 28 was excluded are shown in Table 5. The results almost were very similar and no significant difference was observed from the previous analysis except age for 18–24 (OR:1.191, 95% CI, P = 1.038–1.367, p = 0.013) and 6–9 years of education (OR:1.118, 95% CI, P = 1.024–1.221, p = 0.013).

Table 4

Relationship between Oxford happiness scores, health status and demographic variables.

	Univariate regression		Multivariate p value regression
	OR(95% CI)	p value	OR(95% CI)	p value
Age (years)
45–65	1.00 (ref)	-	1.00(ref)	-
35–44	1.203 (1.109–1.305)	<0.001	1.161(1.064–1.268)	0.001
25–34	1.251 (1.152–1.357)	<0.001	1.190(1.088–1.302)	<0.001
18–24	1.274(1.118–1.405)	<0.001	1.136(0.987–1.307)	0.075
Gender
Male	1.00 (ref)	-	1.00(ref)	-
Female	1.117(1.055–1.183)	<0.001	1.021(0.899–1.160)	0.747
Education level (years)
13≤	1.00(ref)	-	1.00(ref)	-
10–12	1.334(1.238–1.437)	<0.001	1.271(1.174–1.377)	<0.001
6–9	1.130(1.041–1.227)	0.004	1.041(0.951–1.139)	0.387
1–5	1.284(1.176–1.401)	<0.001	1.129(1.024–1.245)	0.015
Employment
Employed	1.00(ref)	-	1.00(ref)	-
Housewife	1.231(1.160–1.306)	<0.001	1.231(1.079–1.403)	0.002
Retired	0.798(0.650–0.979)	0.031	0.877(0.703–1.093)	0.243
Student	1.333(1.070–1.662)	0.010	1.430(1.130–1.810)	0.003
Unemployed	2.261(1.922–2.660)	<0.001	1.704(1.432–2.029)	<0.001
Income status(self-reported)
Good/Very good	1.00(ref)	-	1.00(ref)	-
Intermediate	1.030(0.959–1.106)	0.418	0.997(0.925–1.075)	0.937
Poor/Very poor	1.708(1.559–1.871)	<0.001	1.553(1.406–1.716)	<0.001
Self-rated health
Very good	1.00(ref)	-	1.00(ref)	-
Good	1.147(1.060–1.242)	0.001	1.144(1.056–1.239)	0.001
Fair	1.419(1.312–1.534)	<0.001	1.417(1.310–1.534)	<0.001
Poor	3.062(2.779–3.373)	<0.001	3.085(2.798–3.403)	<0.001
Very Poor	5.073(4.461–5.768)	<0.001	5.114(4.490–5.824)	<0.001

Table 5

Relationship between Oxford happiness scores (without item 28), health status and demographic variables.

	Univariate regression		Multivariate p value regression
	OR(95% CI)	p value	OR(95% CI)	p value
Age (years)
45–65	1.00 (ref)	-	1.00(ref)	-
35–44	1.230 (1.136–1.332)	<0.001	1.200(1.102–1.307)	<0.001
25–34	1.254 (1.158–1.359)	<0.001	1.211(1.110–1.323)	<0.001
18–24	1.315(1.157–1.495)	<0.001	1.191(1.038–1.367)	0.013
Gender
Male	1.00 (ref)	-	1.00(ref)	-
Female	1.123(1.061–1.188)	<0.001	1.033(0.913–1.169)	0.609
Education level (years)
13≤	1.00(ref)	-	1.00(ref)	-
10–12	1.374(1.277–1.479)	<0.001	1.308(1.209–1.414)	<0.001
6–9	1.215(1.121–1.316)	<0.001	1.118(1.024–1.221)	0.013
1–5	1.326 (1.216–1.445)	<0.001	1.168(1.062–1.285)	0.001
Employment
Employed	1.00(ref)	-	1.00(ref)	-
Housewife	1.234(1.164–1.309)	<0.001	1.192(1.049–1.354)	0.007
Retired	0.815(0.669–0.993)	0.042	0.916(0.742–1.131)	0.417
Student	1.332(1.069–1.659)	0.010	1.415(1.121–1.787)	0.004
Unemployed	2.212(1.872–2.614)	<0.001	1.623(1.360–1.938)	<0.001
Income status(self-reported)
Good/Very good	1.00(ref)	-	1.00(ref)	-
Intermediate	1.069(0.996–1.146)	0.063	1.032(0.959–1.110)	0.400
Poor/Very poor	1.812(1.654–1.986)	<0.001	1.642(1.488–1.812)	<0.001
Self-rated health
Very good	1.00(ref)	-	1.00(ref)	-
Good	1.125(1.043–1.214)	0.002	1.123(1.040–1.213)	0.003
Fair	1.326(2.229–1.431)	<0.001	1.324(1.226–1.429)	<0.001
Poor	2.653(2.407–2.925)	<0.001	2.672(2.421–2.984)	<0.001
Very Poor	4.134(3.626–4.714)	<0.001	4.148(3.633–4.736)	<0.001

Discussion

This study investigated the relationship between happiness and self-rated health in 19499 adults aged 18 to 65 years in Iran. To the best of our knowledge, this is the first Iranian national study that investigates the relationship between happiness and self-rated health among adult populations in Iran, a country located in a conflict area, and faces several challenges, including economic sanctions. However, the data presented in the current study confirmed that happiness, to a large extent, is dependent on health and some socioeconomic factors related to income and employment. Specifically, although the findings add a little to knowledge, the main rationale for the study could be that this relation was explored in the Iranian context. In doing so it was suggested to examine the relationship between item 15 of the Oxford Happiness Questionnaire (I am very happy) and self-rated health and see how the correlation compares with similar findings among other nations. The result showed that the correlation between item 15 and self-rated health is about 0.12 well below findings from other countries (see S1 Appendix) [34].

Although 2020 coincided with the Covid-19 pandemic, and Covid-19 as a health-threatening factor can affect the level of happiness [35], we were fortunate to collect the data before the pandemic began in Iran. The first tow of deaths related to COVID-19 was reported on February 19, 2020, in Iran [36] while we collected the data in early January 2020.

The findings suggest that individuals who reported lower health status were more likely to report unhappiness even after controlling for various demographic and socioeconomic factors. This result is in good agreement with those of previous investigations where it has been reported that self-rated health is an important determinant of happiness, or quantitatively much more important than other demographic and economic characteristics [37,38]. Similar studies, showing that when people suffer from a severe illness or are in pain, their capacity for happiness is impaired. For example, chronic physical disease, mood, anxiety, and other mental disorders can significantly reduce happiness [39].

Also, the current study showed that employment status and income independently influenced happiness. Unemployed people are more likely to be unhappy than employed people, and people who reported lower income levels were more likely to be unhappy than those who had higher income. These results support a previous study that demonstrated that happy people were more likely to be employed and earn more than unhappy people [40]. The finding from another study that investigated the association between income and happiness in East and South Asia, including China, Singapore, Japan, India, Malaysia, Philippines, South Korea, Thailand, Taiwan, Hong Kong, showed that associations between income and happiness were strongly significant in some countries, including South Korea and Taiwan [41]. Thus policies aimed at increasing employment and reducing income disparities may increase happiness in individuals.

Strengths and limitations

The study benefited from relatively large sample size and included people living in rural and urban communities with different socio-economic backgrounds. Another notable strength was the precision of the data collection by the trained interviewers. However, one might consider the probability of a socially desirable response behavior in the direct contact between interviewers and respondents. Thus the interpretation of the results needs caution.

Multistage sampling can simplify data collection when we have large, geographically spread samples, and we can obtain a probability sample without a complete sampling frame. However, it can lead to unrepresentative samples because large sections of populations may not be selected for sampling. Since we used multistage sampling, the result might not be generalized to all Iranians.

One should bear in mind that the Oxford Happiness Questionnaire covers a wide range of traits rather than happiness in the sense of life satisfaction [33]. Perhaps in future studies, if we are going to measure happiness in the sense of life satisfaction, there is a need to use an appropriate measure. In addition, item 28 of the Oxford Happiness Questionnaire is about self-rated health, and thus it might cause autocorrelation with the self-rated health measure, although the item 28 and the measure of self-rated health are worded differently. The latter is negative (I do not feel particularly healthy) while the former is positive and askes people to rate their current health. However, as indicated in reanalysis of the data (Table 5), the findings did not show any major differences to our earlier analysis as shown in Table 4.

Conclusion

The results obtained from the current study confirmed that a strong relationship exists between health and happiness. Self-rated health was the most influencing factor affecting happiness even after adjusting for socioeconomic variables. It seems that adopting policies to improve public health and placing health on the public agenda could be an effective approach for increasing happiness.

The correlations between health and happiness in selected studies.

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1 Dec 2021

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Reviewer #1: This is an elementary report of a well-known relationship and is OK in itself. but adds little to knowledge.

The main rationale is to show this relation in Iranian context. In the context of that goal the authors should compare the strenghts of the correlations with similar studies conducted in other countries.

Doing so, they might consider to compare with correlations between happiness and health gathered in the World Database of Happiness, at https://worlddatabaseofhappiness.eur.nl/search-the-database/correlational-findings/#id=-1yD-HsBSlHDfFpgD2EY. This would require that they use item 15 from the OHQ rather than the full scale.

The use of the OHQ should be reconsidered anyway. A look at the items shows that it covers a wide range of positive traits rather than happiness in the sense of life-satisfaction. Item 28 is about self-rated health and causes autocorrelation.

In the discussion section the authos acknowledge that the correlation may be driven by an effect of happiness on health, but in the conclusion they attribute the correlation to the effects of health on happiness

Reviewer #2: The results of this paper are interesting, and can contribute to the literature on happiness and health among adults.

However, several revisions are required for this work to be accurately portrayed, received, and interpreted. Below, I have separated my comments into an overall comment.

- The first paragraph should include some comparative statistics on figures/statistics from EMRO region countries to provide the context for Iran being similar (in terms of happiness and health).

- The validity and reliability of the questionnaire (Oxford standard Happiness Questionnaire & Self-rated health) among the Iranian population should be justified in detail.

- In table 1; write the scale of Education & Income.

- More discussion about the justification of finding should be provided in this section. The discussion is disorganized and confusing. It is better to summarize your findings firstly and then discuss them separately.

- The conclusion is the repetition of what has been said in the text! And need a revision based on results.

- The manuscript needs a revision for grammar, typos, and English expressions to improve the readability.

**********

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Reviewer #1: Yes: Ruut Veenhoven

Reviewer #2: Yes: Vahid Rashedi

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17 Jan 2022

Forough Mortazavi

Academic Editor

PLOS ONE

12 January 2022

Dear Dr. Mortazavi,

PONE-D-21-28962

The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults

PLOS ONE

Thank you for your e-mail. We are grateful to both reviewers and found their comments very helpful. We have revised the manuscript and now very pleased to submit the revised version for your consideration. All changed are marked in blue and hope you find it satisfactory.

Wish you all the best.

Yours sincerely

Ali Montazeri

When submitting your revision, we need you to address these additional requirements.

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Thank you. Done.

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We will update your Data Availability statement to reflect the information you provide in your cover letter.

This following sentences add to the manuscript.

Data Availability

The datasets generated for this study are fully available without restriction.

3. Please include your full ethics statement in the ‘Methods’ section of your manuscript file. In your statement, please include the full name of the IRB or ethics committee who approved or waived your study, as well as whether or not you obtained informed written or verbal consent. If consent was waived for your study, please include this information in your statement as well.

Done.

Ethics statement

The National Institutes for Medical Research Development (NIMAD), Tehran, Iran. ethics committee approved the study (IR.NIMAD.REC.l398.228). Due to the study design and all participants gave their verbal consent.

Additional Editor Comments

Dear authors,

Thank you for submitting your manuscript to PLOS ONE. According to the reviewers’ comments and my evaluation, several points needs careful attention.

1. The abstract should be rewritten using a structured format.

Done.

2. In the methods section, the authors should describe the sampling method and the procedures for selecting the participants in detail.

The following sentences were added to the Methods as requested:

To estimate the sample size, according to a national study [30], and based on population density, the country was classified into five categories. Then, samples were selected based on multi-stage sampling from each category. In doing so, one province was randomly selected from each category. Then two cities and two rural settings were randomly selected in each province. Every household within the city and rural areas had the same probability of being sampled. The households to be sampled were selected using systematic sampling within each census section. Finally, sampling units (the individuals) were selected randomly from all eligible persons living in the same household. Informed consent was obtained from each individual after the purpose of the study was explained. Considering the effect size of 1.4, the sample size of 20320 was estimated. However, in practice, 19499 Iranian adults were entered into the study.

3. This study was performed during the covid-19 pandemic. This may have effected on the selection of the sample.

The study was carried out just before pandemic. To satisfy the reviewer’s comment we added the following sentences to the first paragraph of Discussion:

Although 2020 coincided with the Covid-19 pandemic, and Covid-19 as a health-threatening factor can affect the level of happiness [37], we were fortunate to collect the data before the pandemic began in Iran. The first tow of deaths related to COVID-19 was reported on February 19, 2020, in Iran [38] while we collected the data in early January 2020.

4. The pandemic may have affected both the level of happiness and perceived health. This should be taken into consideration in comparisons with the findings of previous studies in the discussion section.

Please see the above.

5. PLS consider the STROBE checklist for reports of observational studies and revise the manuscript taking the following points into account:

6. Describe the setting, locations, and relevant dates, including periods of data collection.

Done.

This was a national cross-sectional study conducted from 10 January to 20 January 2020 throughout all provinces in Iran. Currently Iran has 32 provinces with over 80 million populations.

7. Describe any efforts to address potential sources of bias.

Done.

Please see strengths and limitations.

8. Explain how missing data were addressed.

Done.

Please see strengths and limitations.

9. Discuss limitations of the study, taking into account sources of potential bias or imprecision.

Done.

Please see strengths and limitations.

10. Discuss both direction and magnitude of any potential bias.

Done.

Please see strengths and limitations.

11. Discuss the generalizability of the study results.

Done.

Please see strengths and limitations.

12. Limitations must be further explained in relation to sampling method.

Thank you. There was no limitation in relation to sampling method. However, we included a separate section on strengths and limitations. Hope you find it satisfactory.

Please see strengths and limitations. Multistage sampling can simplify data collection when we have large, geographically spread samples, and we can obtain a probability sample without a complete sampling frame. However, it can lead to unrepresentative samples because large sections of populations may not be selected for sampling. Since we used multistage sampling, the result might not be generalized to all Iranians.

Review Comments to the Author

Reviewer #1 Prof. Ruut Veenhoven

This is an elementary report of a well-known relationship and is OK in itself. but adds little to knowledge. The main rationale is to show this relation in Iranian context. In the context of that goal the authors should compare the strengths of the correlations with similar studies conducted in other countries. Doing so, they might consider to compare with correlations between happiness and health gathered in the World Database of Happiness, at https://worlddatabaseofhappiness.eur.nl/search-the-database/correlational-findings/#id=-1yD-HsBSlHDfFpgD2EY. This would require that they use item 15 from the OHQ rather than the full scale.

Specifically, although the findings add a little to knowledge, the main rationale for the study could be that this relation was explored in the Iranian context. In doing so it was suggested to examine the relationship between item 15 of the Oxford Happiness Questionnaire (I am very happy) and self-rated health and see how the correlation compares with similar findings among other nations. The result showed that the correlation between item 15 and self-rated health is about 0.64 and is very similar with other studies (see S1 Appendix) [36].

The use of the OHQ should be reconsidered anyway. A look at the items shows that it covers a wide range of positive traits rather than happiness in the sense of life-satisfaction. Item 28 is about self-rated health and causes autocorrelation.

We agree. However, at this stage it is impossible to reconsider the happiness measurement. However, we added the following statement to the limitation to comply with the recommendation:

One should bear in mind that the Oxford Happiness Questionnaire covers a wide range of traits rather than happiness in the sense of life satisfaction [44]. Perhaps in future studies, if we are going to measure happiness in the sense of life satisfaction, there is a need to use an appropriate measure. In addition, item 28 of the Oxford Happiness Questionnaire is about self-rated health, and thus it might cause autocorrelation with the self-rated health measure, although the item 28 and the measure of self-rated health are worded differently. The latter is negative (I do not feel particularly healthy) while the former is positive and askes people to rate their current health.

In the discussion section the authors acknowledge that the correlation may be driven by an effect of happiness on health, but in the conclusion they attribute the correlation to the effects of health on happiness.

Thank you for your comment. We agree that we made a mistake and thus the paragraph was deleted.

Reviewer #2: Dr. Vahid Rashedi

The results of this paper are interesting, and can contribute to the literature on happiness and health among adults. However, several revisions are required for this work to be accurately portrayed, received, and interpreted. Below, I have separated my comments into an overall comment.

Thank you for your positive evaluation and comments.

- The first paragraph should include some comparative statistics on figures/statistics from EMRO region countries to provide the context for Iran being similar (in terms of happiness and health).

According to the world happiness report (2017-2019), the highest and lowest happiness scores were for Finland and Afghanistan, respectively. The Islamic Republic of Iran ranked 118th among 153countries. Although happiness score in Iran was lower than some countries in the Eastern Mediterranean Region (EMRO), such as Saudi Arabia, Pakistan, Morocco, but was higher than some other countries including Jordan, Tunisia, and Egypt [6].

One of the most frequently used measures of self-reported health status is a single question asking individuals to rate their overall health on a scale from excellent to very poor. There is widespread agreement that this simple global question provides a useful summary of how individuals perceive their overall health status [7]. The results of a cross-national study that compared health in Egypt, Iran, Jordan, and the United States showed that means and standard deviations of self-rated health by country was (2.79±0.85), (2.99±0.81), (3.06±0.83), and (3.23±0.78), respectively [8].

- The validity and reliability of the questionnaire (Oxford standard Happiness Questionnaire & Self-rated health) among the Iranian population should be justified in detail.

Thank you. Both of them were added in detail.

Psychometric properties of the Iranian version of questionnaire are well documented. Cronbach's alpha coefficient (measure of internal consistency) and interclass correlation coefficient (measure of stability) were 0.90 and 0.79, respectively. The convergent and divergent validity of the questionnaire were high and acceptable [32].

Validity and reliability of self-rated health measure among Iranian showed acceptable results. The criterion validity showed that the self-rated health and the WHO-5 well-being had positive correlation as expected (r= 0.5, p< 0.001). Additionally, the reliability of the self-rated health, using interclass correlation coefficient (ICC), was found to be 0.83; 95% CI (0.72 to 0.90) [35].

- In table 1; write the scale of Education & Income.

The scales were included.

Education: year

Income: self-reported

- More discussion about the justification of finding should be provided in this section. The discussion is disorganized and confusing. It is better to summarize your findings firstly and then discuss them separately.

Done.

Please see discussion

- The conclusion is the repetition of what has been said in the text! And need a revision based on results.

Thank you for your comment. The conclusion was revised.

It seems that adopting policies to improve public health and placing health on the public agenda could be an effective approach for increasing happiness.

- The manuscript needs a revision for grammar, typos, and English expressions to improve the readability.

Thank you. The manuscript was copy edited once more.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

27 Jan 2022

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

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We look forward to receiving your revised manuscript.

Kind regards,

Forough Mortazavi

Academic Editor

PLOS ONE

Additional Editor Comments:

Dear authors,

Thank you for revising the manuscript according to the reviewers’ comments; however, a few points still remain. Please kindly consider the points raised by reviewer 1 regarding item 28 and auto-correlation. In presenting the results of statistical analyses, please describe how the authors divided the sample into two groups of low and high happiness for logistic regression analyses. This section is in need of further clarification. Also, in the titles of tables 2 and 3, PLS replace 'happiness' with the correct description, i.e. 'Oxford happiness scores’.

Regards,

[Note: HTML markup is below. Please do not edit.]

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: (No Response)

Reviewer #2: All comments have been addressed

**********

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: Partly

Reviewer #2: Yes

**********

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: Yes

**********

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

**********

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: My objection about auto-correlation is not met. The answer that the concerned questions on health were formulated differently does not convince. Without re-analysis of the data I cannot recommend acceptance.

Reviewer #2: I read the manuscript with great interest and think the data reported in this study is valuable, and the authors have made all the corrections to the article entitled: "The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults".

**********

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.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

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: Yes: Ruut Veenhoven

Reviewer #2: Yes: Vahid Rashedi

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

12 Feb 2022

Forough Mortazavi

Academic Editor

PLOS ONE

1 February 2022

Dear Dr. Mortazavi,

PONE-D-21-28962

The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults

PLOS ONE

Thank you for your e-mail and the comments. We have revised the manuscript and now pleased to submit the second revision for your consideration. Hope you find revisions satisfactory.

Wish you all the best.

Yours sincerely

Ali Montazeri

Editor Comments:

Please kindly consider the points raised by reviewer 1 regarding item 28 and auto-correlation.

Thank you for your comment. The point was responded. Please see reviwer1.

In presenting the results of statistical analyses, please describe how the authors divided the sample into two groups of low and high happiness for logistic regression analyses. This section is in need of further clarification.

The following sentence was added to the statistical analysis as requested:

Logistic regression analyses were performed to assess the relationship between happiness and independent variables, including participants’ health status. As such happiness as dependent variables was categorized into: ‘happy’ (scores ranging from 4 to 6) and ‘unhappy’ (scores ranging from 1 to 3).

Also, in the titles of tables 2 and 3, PLS replace 'happiness' with the correct description, i.e. 'Oxford happiness scores’.

Thank you. Done.

Reviewers'Comments to the Author

Reviewer #1 Prof. Ruut Veenhoven

My objection about auto-correlation is not met. The answer that the concerned questions on health were formulated differently does not convince. Without re-analysis of the data I cannot recommend acceptance.

Thank you for your comment. The correlation between happiness without item 28 and self-reported health examined and now was added to Appendix.

Perhaps in future studies, if we are going to measure happiness in the sense of life satisfaction, there is a need to use an appropriate measure. In addition, item 28 of the Oxford Happiness Questionnaire is about self-rated health, and thus it might cause autocorrelation with the self-rated health measure, although the item 28 and the measure of self-rated health are worded differently. The latter is negative (I do not feel particularly healthy) while the former is positive and askes people to rate their current health. However, we did examine this correlation and found the correlation coefficient to be 0.17 (See S1 Appendix).

Reviewer #2: Dr. Vahid Rashedi

I read the manuscript with great interest and think the data reported in this study is valuable, and the authors have made all the corrections to the article entitled: "The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults".

Thank you for comments and time spent to review this paper.

Submitted filename: Response to Reviewers.2.docx

Click here for additional data file.

21 Feb 2022

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

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We look forward to receiving your revised manuscript.

Kind regards,

Forough Mortazavi

Academic Editor

PLOS ONE

Additional Editor Comments:

Dear authors,

Thank you for revising your manuscript. Based on comments by reviewer #1 and my own evaluation, an important point raised still remains unaddressed. PLS take note that without the approval of reviewer # 1, the manuscript cannot be accepted for publication. I strongly recommend that you reanalyze the data after removing the items pointed out by reviewer #1.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

27 Feb 2022

Forough Mortazavi

Academic Editor

PLOS ONE

Thank you for your e-mail and the comments. We have revised the manuscript and now pleased to submit the third revision for your consideration. Hope you find revisions satisfactory.

Wish you all the best.

Yours sincerely

Ali Montazeri

Editor Comments:

Based on comments by reviewer #1 and my own evaluation, an important point raised still remains unaddressed. PLS take note that without the approval of reviewer # 1, the manuscript cannot be accepted for publication. I strongly recommend that you reanalyze the data after removing the item pointed out by reviewer #1.

Thank you. All comments were attended as suggested. The following revisions were applied:

1. Methods (Statistical analysis):

Data were explored using descriptive statistics, including frequency, percentage, mean and standard deviation. Logistic regression analyses were performed to assess the relationship between happiness and independent variables, including participants’ health status. However, since some eminent scholars [36] believe that there is an auto-correlation between item 28 and the self-rated health, we did reanalyze the data while item 28 (I do not feel particularly healthy) was excluded from the Oxford happiness score. As such for both with and without item 28 of the Oxford questionnaire, happiness as dependent variables were categorized into: ‘happy’ (scores ranging from 4 to 6) and ‘unhappy’ (scores ranging from 1 to 3). The results expressed as odds ratio and 95% confidence intervals. A significant level was set at P< 0.05.

2. Results:

The results are shown in Table 3. In addition, the results obtained from the same analysis when items 28 was excluded are shown in Table 4. The results almost were very similar and no significant difference was observed from the previous analysis except for age 18-24 (OR:1.191, 95% CI, P= 1.038-1.367, p= 0.013) and 6-9 years of education (OR:1.118, 95% CI, P= 1.024-1.221, p= 0.013).

3. Strengths and limitations

In addition, item 28 of the Oxford Happiness Questionnaire is about self-rated health, and thus it might cause autocorrelation with the self-rated health measure, although the item 28 and the measure of self-rated health are worded differently. The latter is negative (I do not feel particularly healthy) while the former is positive and askes people to rate their current health. However, as indicated in reanalysis of the data (Table 4), the findings did not show any major differences to our earlier analysis as shown in Table 3.

Submitted filename: Response to Reviewers.3.docx

Click here for additional data file.

7 Mar 2022

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Forough Mortazavi

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

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: (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: Partly

**********

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

Reviewer #1: 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)

**********

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

**********

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: In an earlier comment I noted that the the Oxford happiness scale involves an item on health, which causes auto correlation. I advised to recalculate, leaving this item out

I also noted that this questionaire covers broader matters than happiness as discussed in the introduction, and advised to calculate correlations for the few items on life-satisfaction separately

The authors did not recalculate, but sufficed mentioning these points under limitations. In my view, that is not acceptable

Still another point: the authors write Despite the importance of studying the relationship between happiness and health, only a few

81 small-scale studies have been conducted in Iran [21- 24] They are apparently unaware of the 337 findings on this topic listed in the World Database of happiness at https://worlddatabaseofhappiness.eur.nl/search-the-database/correlational-findings/#id=N1iFWn8BRfHHvZHVJh7X

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Reviewer #1: Yes: Ruut Veenhoven

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8 Mar 2022

Dr. Forough Mortazavi

Academic Editor

PONE-D-21-28962

The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults

PLOS ONE

Thank you for your e-mail and the comments. We have revised the manuscript and now pleased to submit the fourth revision for your consideration. Hope you find revisions satisfactory.

Wish you all the best.

Yours sincerely

Ali Montazeri

Submitted filename: Response to Reviewers.R4.docx

Click here for additional data file.

10 Mar 2022

The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults

PONE-D-21-28962R4

Dear Dr. Montazeri,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Forough Mortazavi

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

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

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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

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

Reviewer #1: Yes

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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: Yes

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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

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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)

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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: Yes: Ruut Veenhoven

15 Mar 2022

PONE-D-21-28962R4

The relationship between happiness and self-rated health: A population-based study of 19499 Iranian adults

Dear Dr. Montazeri:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Forough Mortazavi

Academic Editor

PLOS ONE