Relationship between Noise Annoyance and High Blood Pressure in Workers Exposed to Chronic Noise Among the Workers of an Automotive Industry.

BACKGROUND: Chronic exposure to noise in workplaces is one of the most important physical agents that affects workers' health and causes social and individual problems. The aim of this study was to investigate the relationship between noise annoyance and blood pressure (BP) of workers of an automotive industry.
METHODS: In this cross-sectional study, 250 workers were randomly selected. The subjects were classified in two groups based on the exposure to sound pressure levels lower and higher than 85 dB (106 and 144 workers, respectively). In this study, BP was measured using an ALPK2 mercury pressure gauge. To measure annoyance levels, an annoyance questionnaire containing a numerical question numbered 0-11 was used.
RESULTS: The mean age of the subjects was 36.19 (±3.75) years. The results showed that the systolic (SBP) and diastolic blood pressure (DBP) of the subjects exposed to the sound pressure levels higher than 85 dB were significantly higher than those exposed to a sound pressure level lower than 85 dB (P < 0.01). Also, the results of the multivariate regression showed a significant relationship between the annoyance and DBP and SBP caused by chronic exposure to noise and sound pressure levels (P < 0.01).
CONCLUSION: The results of this study showed that the annoyance caused by exposure to chronic noise in the workplace causes stress in the workers and, in the long term, could increase the risk of high SBP and DBP. Copyright:

INTRODUCTION

Noise is a harmful and annoying physical agent which seriously threatens human health,[12] and is the second cause of heart attacks in workplaces.[3] Furthermore, it is considered as the third most dangerous pollutant in workplaces by The World Health Organization.[4] The effects of noise on human health include neuropsychological effects, adverse impacts on the balance system, damage to hearing system, reduced cardiac output, increased number of breaths and effects on BP.[5] Chronic exposure to noise) exposure more than three years) causes physiological and psychological disorders as well as the change in heart rate and BP.[6] Hypertension is one of the consequences of chronic exposure to noise among workers.[7] Factors such as age, sex, diet, smoking, and occupational exposures are also known as the main factors influencing BP.[8] Besides, exposure to sound pressure levels higher than 85 dB may affect work efficiency and speech interference.[9] The mechanism of relationship between noise and BP is not clearly known. High levels of noise seem to cause adrenaline secretion and constriction of the peripheral arteries, resulting in increased BP. Given the high importance of hypertension in public health, and the presence of noise in most workplaces, any relationship between them will be very important.[1011]

The physiological and psychological effects of noise such as physical and mental exhaustion, stress and anxiety, dizziness, headache, anger, aggressive behavior, distraction, noise annoyance, reduced work efficiency, temporary and even permanent deafness often appear gradually and in the long term.[12] Noise annoyance, as one of the negative effects of exposure to noise and its most common mental response, has attracted the attention of many researchers, policymakers, and the public. Annoyance is a measurable mental response and can be considered as an indicator for other adverse effects of noise.[13] Annoyance is an unclear condition associated with discomfort, distress, anger, grief, disappointment, and depression. WHO has described annoyance as a sense of individual or group discomfort related to damaging effects of materials or conditions. Generally, noise-induced annoyance is a feeling of discomfort caused by unwanted noise.[13] In addition, noise annoyance is more common among older people compared to young ones exposed to noise.[14] Annoyance, which is one of the consequences of chronic exposure to noise, is associated with cardiovascular diseases.[15] In the workplace, people with more sensitivity to noise are more likely to have cardiovascular problems.[16] Some studies have indicated that people with noise sensitivity and annoyance had symptoms such as hypertension, sleep disorders and stress.[17] Given that, this study aimed to investigate the relationship between noise annoyance and BP of workers of an automotive industry in Tehran.

MATERIALS AND METHODS

This is an analytical-descriptive study conducted among workers of an automotive industry in 2017. Inclusion criteria included no hypertension when hiring, no chronic diseases including diabetes, cardiovascular diseases, kidney diseases and COPD, no malignancy, not taking hypertension medications, and not taking corticosteroid drugs. Those who had these conditions were included in the study with informed consent. The study participants were 250 that selected randomly. Occupational exposure to noise was calculated in terms of 8-h pressure level, according to ISO 9612: 2009, using the Testo sound level meter (model CEL-815). Subjects were then divided into two groups based on exposure to noise levels below 85 dB and greater than 85 dB and their data were compared. Demographic data such as age, work experience, and education level were collected through a general questionnaire. BP was measured in two groups using an ALPK2 mercury gauge. Subjects’ SBP (Systolic Blood Pressure) and DBP (Diastolic Blood Pressure) were measured twice; once in the morning before starting work and once again after 30 min of doing physical activity. Before the BP was measured, people sat in the chair for 5 min. High blood pressure was defined as mean SBP (at rest) more than 140 mmHg or mean DBP (at rest) more than 90 mmHg.[18] A questionnaire was used to determine the level of noise annoyance. The questionnaire had a question with a numerical scale of 0 to 11. Larger numbers indicate a higher rate of noise annoyance.

Ethical Clearance

Ethical approval for this study (Ethical Committee IR.IUMS.REC 1395.9411139003) was provided by the Iran University of Medical Sciences, Iran.

Statistical method

All data were analyzed using SPSS.22. Descriptive statistics (mean and standard deviation) were used to describe the data. Then, using Kolmogorov–Smirnov test, the normalization of quantitative data was verified and confirmed. In order to analyze the data, examine the simultaneous effects of noise annoyance and sound pressure level on BP, and investigate the relationship between qualitative variables, we used the independent t-test, the linear regression, and the Chi-square test, respectively. All the tests were done with an error rate of 5%.

RESULTS

The mean age of subjects with exposure to noise greater than 85 dB and less than 85 dB were 36.08 ± 3.44 and 36.28 ± 3.81, respectively. There was no significant difference between the two groups in terms of age (P = 0.631). Also, the mean work experiences of the two groups in terms of exposure to sound pressure level was 15.10 (±3.88) and 14.91 (±3.57) years, respectively, and no statistically significant difference was observed (P = 0.450). Regarding education levels, most of the subjects in both groups had a diploma (183 people (73.2%) and a significant relationship was found between the two groups in terms of education levels (P = 0.034) (Workers with a higher level of education were less exposed to Lepd >85, and those with a lower level of education were more exposed to Lepd ≤85). A majority of the individuals exposed to lower-than-85 dB sound pressure level (233 (93.3%)) and higher-than-85 dB (17 (6.8%)) were married. Table 1 shows the results of comparing the demographic variables of the two groups.

Table 1

Comparison of demographic and background variables in terms of exposure to sound pressure levels

		LEpd		Total Mean (±SD)	t	P
		≤85 Mean (±SD)	>85 Mean (±SD )
Age (year)		36.06 (±3.44)	36.28 (±3.81)	36.19 (±3.75)	0.480	0.631
Experience (year)		14.91 (±3.57)	15.10 (±3.88)	15.02 (±2.04)	0.757	0.450
		Number (%)	Number (%)	Total Number (%)	χ2	P
Education	Diploma	80 (32%)	103 (41.2%)	183 (73.2%)	6.74	0.034
	Associate degree	15 (6%)	35 (14%)	50 (20)
	Bachelor’s degree and more	11 (4.4%)	6 (2.4%)	17 (6.8%)
marriage status	single	9 (3.6%)	8 (3.2%)	17 (6.8%)	0.830	0.362
	married	97 (38.8%)	136 (54.4%)	233 (93.2%)

Table 2 shows a significant relationship between noise annoyance and DBP and SBP in the two groups under study (P < 0.001).

Table 2

Relationship between noise annoyance and DBP and SBP and exposure to sound pressure levels using independent t-test

Variable	LEpd		P	t
	≤85 Mean±SD	>85 Mean±SD
SBP	115.69±14.77	135.99±14.40	<0.001	10.97
DBP	83.74±6.25	90.73±3.84	<0.001	10.43
Annoyance	5.18±1.22	8.20±1.77	<0.001	17.17

The use of multiple linear regression to examine if annoyance and sound pressure levels had a significant relationship with SBP and DBP showed that there was a significant relationship between annoyance and SBP and DBP, and also between sound pressure levels and SBP and DBP. According to the results of multiple linear regression, the obtained equations for SBP and DBP were SBP = 109.495-10.513 LEpd + 3.267Annoyance and DBP = 82.107-3.810 LEpd + 1.051 Annoyance, respectively. Based on these two equations, in case of constant sound pressure level, each unit of increase in annoyance would averagely increase the DBP by 1.05 and the SBP by 3.26 [Table 3].

Table 3

Relationship between sound pressure level and noise annoyance and SBP and DBP using multiple linear regression

Variable	LEpd		Annoyance
	β (sd)	P	β (sd)	P
SBP	−3.811 (0.98)	<0.001	3.266 (0.36)	0.004
DBP	−10.512 (0.36)	<0.001	1.052 (0.27)	0.005

DISCUSSION

The results of this study, which aimed to investigate the relationship between the annoyance caused by chronic exposure to noise in an industrial environment and the BP of the workers, clearly showed the effects of exposure to noise and the annoyance caused by it on SBP and DBP.

In psychology, noise pollution refers to unpleasant and/or unwanted sound, which is quantitatively a combination of waves and intensities with different sound levels that does not have a specific composition and is not pleasant to hearing system. It may cause annoyance and psychotic disorders in workers.[12]

In a prospective study by Lee et al. in Busan, Korea, on 916 male workers in a metal production plant, the effects of chronic exposure to noise on BP was measured, and it was indicated that the mean SBP in the exposed group to sound pressure higher than 85 dB was 3.8 mm Hg more than that of the base group, and this difference was statistically significant, but the mean DBP did not show a significant difference, and this could be attributed to the role of the workers’ noise annoyance in affecting SBP.[19] These results were consistent with those of our study, that is, SBP and DBP of the workers at sound pressure levels lower and higher than 85 dB had a significant difference, which could be attributed to the resulting brain activity and noise annoyance.

In previous field studies, workers who were exposed to high levels of sound showed an increase in their BP during exposure and even several hours after that, suggesting that this increase in BP could be due to the stress and noise annoyance in the workers.[20] In their studies, Lusk and Kalantari et al. reported a significant increase in DBP and SBP of the workers exposed to chronic noise[21] in an industrial environment similar to the automotive industry. The results of their study are consistent with ours in terms of increased SBP and DBP in workers with noise-induced annoyance. In a study carried out on noise annoyance and high BP, Babisch et al. found that exposure to noise was associated with increased BP.[22] They suggested that using protective equipment to reduce the surrounding sound and the structure and types of houses could act as moderators. Another study by Babisch et al. on the relationship between noise annoyance due to exposure to aircraft sound and increased risk of hypertension indicated that there was a significant and positive relationship between exposure to noise and high BP.[23] This relationship was higher among people with higher noise annoyance compared to those without it. Ndrepepa also concluded in his study that there was a positive and significant relationship between the annoyance caused by exposure to traffic noise and the increased risk of arterial pressure.[15]

Chang et al. also stated in their study that only SBP had increased in the industrial environment, but Talbott et al. reported that only DBP had increased.[924] Besides, studies such as that of Melamed et al. did not reported such a significant increase neither in SBP nor DBP.[25]

The protocols and reference papers as well as the studies carried out on this issue also made it clear that the sound pressure level over 85 dB had mainly physical and psychological damage and acute effects, and only stated the possibility of increased risk of hypertension and other cardiovascular diseases.[26] However, the results of this study, as well as those of other related studies, showed that in a constant sound pressure level, the noise annoyance caused by prolonged exposure to noise could be associated with increased SBP and DBP by 1.05 and 3.26 times, respectively, which would result in an increased risk of cardiac disorders.

CONCLUSION

In general, the researchers concluded that SBP and DBP changes caused by the workers’ noise annoyance in industrial environments could be recognized as a risk factor and needed to be carefully examined due to the multivariate nature of BP and the presence of physical and chemical confounders in the work environments.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This research was financially supported by Iran University of Medical Sciences.

Conflicts of interest

There are no conflicts of interest.