Effect of Acute Exposure to Loud Occupational Noise during Daytime on the Nocturnal Sleep Architecture, Heart Rate, and Cortisol Secretion in Healthy Volunteers

First-night effect in insomnia disorder: a systematic review and meta-analysis of polysomnographic findings

Polysomnographic studies have been performed to investigate the first-night effect in insomnia disorder. However, these studies have revealed discrepant findings. This meta-analysis aimed to summarise and quantify the characteristics of the first-night effect in insomnia disorder. We performed a systematic search of the PubMed, Medline, EMBASE, Web of Science and PsycINFO databases to identify studies published through October 2019. A total of 11,862 articles were identified, and seven studies with eight independent populations were included in the meta-analysis. A total of 639 patients with insomnia disorder and 171 healthy controls underwent more than 2 consecutive nights of in-laboratory polysomnography. Pooled results demonstrated that both variables of sleep continuity and sleep architecture, other than slow-wave sleep were significantly altered in the first-night effect in insomnia disorder. Furthermore, the results indicated that patients with insomnia disorder had a disruption of sleep continuity in the first-night effect, including increased sleep onset latency and reduced total sleep time, compared to healthy controls. Overall, the findings show that patients with insomnia disorder experience the first-night effect, rather than reverse first-night effect, and the profiles of the first-night effect in patients with insomnia are different from healthy controls. These indicate that an adaptation night is necessary when sleep continuity and sleep architecture is to be studied in patients with insomnia disorder. More well-designed studies with large samples are needed to confirm the results.

The effects of occupational noise on sleep: A systematic review

Noise exposure in the workplace is one of the most common occupational hazards, which can affect sleep in the human. The effects of occupational noise can be different than that of environmental or social noise. This study aimed to conduct a systematic review on the effects of occupational noise on various characteristics of sleep. In this study, three electronic bibliographic databases (Scopus, PubMed, and Web of Science) were systematically searched up to 14 December 2022. The search algorithm included two sets of keywords and possible combinations. The first group was keywords related to occupational noise, and the second group was keywords related to sleep. A total of 2082 articles were identified in the initial search, and 2034 articles were excluded based on exclusion criteria or lacking inclusion criteria. Finally, 48 articles met the inclusion criteria and were selected for final review. Among 13 articles identified as high quality, all studies (100%) showed that noise had a significant effect on sleep among workers in various occupations. Among 17 articles with moderate quality, thirteen studies (76.47%) indicated that noise had a significant effect on sleep among workers in different occupations. Among 18 low-quality articles, fifteen studies (83.33%) showed that noise had a significant effect on sleep. 41 out of 48 studies (85.42%) found that occupational noise can negatively impact sleep among employees in various occupations. There are at least four potential pathways for this effect, including the physiological effect of daytime noise exposure, the psychological effect of daytime noise exposure, the effect of nighttime noise exposure, and the effect of hearing problems due to noise.

Association between occupational noise exposure and diabetes: A systematic review and meta-analysis

BACKGROUND

In addition to the well-known risk factors of diabetes, evidence is accumulating on the negative role of environmental and occupational factors such as noise exposure. We conducted a systematic review and meta-analysis on the association between long-term occupational noise exposure and diabetes.

METHODS

We systematically searched evidence in PubMed, Scopus, and Web of Science (until August 2022) according to the PRISMA protocol. Risk of bias was assessed using the Newcastle-Ottawa scale. Random-effects meta-analysis was applied separately for risk ratio (odds ratio, relative risk) and hazard ratio. We evaluated the heterogeneity and publication bias. We applied meta-regressions to identify sources of heterogeneity. The overall body of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) framework.

RESULTS

Of 533 retrieved articles, twelve studies (11 on non-gestational, and one on gestational diabetes) on total 106,045 population (23,996 diabetic cases) met our inclusion criteria; of which eight studies were cross-sectional, three were cohorts, and one was case-control. Only 40% of papers (five out of 12) had fair, good or very good quality, and most of the papers had poor or very poor quality in terms of risk of bias. We observed a non-significant increased risk of diabetes in association with occupational noise exposure (combined risk estimates: 1.16, 95% confidence interval [CI]: 0.97: 1.34; I² = 57.7%). Doing separate meta-analyses on cohort and rest of studies, we found similar findings (cohort studies (n = 3): combined risk estimate: 1.17; 95% CI: 0.84: 1.50; I² = 79%; cross-sectional studies (n = 8): combined risk estimate: 1.26; 95% CI: 0.93: 1.58; I² = 50.4%). We found no indication of publication bias.

CONCLUSIONS

The overall evidence on the association between occupational noise exposure and diabetes is heterogeneous, limited, and mostly with low quality. More robust studies in terms of population selection, exposure and outcome assessment, and adjustment for confounders are necessary.

Investigating the combined effect of ALAN and noise on sleep by simultaneous real-time monitoring using low-cost smartphone devices

The association between artificial light at night (ALAN) and noise, on the one hand, and sleep, on the other, is well established. Yet studies investigating these associations have been infrequent and mostly conducted in controlled laboratory conditions. As a result, little is known about the applicability of their results to real-world settings. In this paper, we attempt to bridge this knowledge gap by carrying out an individual-level real-world study, involving 72 volunteers from different urban localities in Israel. The survey participants were asked to use their personal smartphones and smartwatches to monitor sleep patterns for 30 consecutive days, while ALAN and noise exposures were monitored in parallel, with inputs reported each second. The volunteers were also asked to fill in a questionnaire about their individual attributes, daily habits, room settings, and personal health, to serve as individual-level controls. Upon cointegration, the assembled data were co-analyzed using bivariate and multivariate statistical tools. As the study reveals, the effect of ALAN and noise on sleep largely depends on when the exposure occurred, that is, before sleep or during sleep. In particular, the effect of ALAN exposure was found to be most pronounced if it occurred before sleep, while exposure to noise mattered most if it occurred during the sleep phase. As the study also reveals, the effects of ALAN and noise appear to amplify each other, with a 14-15.3% reduction in sleep duration and an 8-9% reduction in sleep efficiency observed at high levels of ALAN-noise exposures. The study helped to assemble a massive amount of real-time observations, enabling a robust individual-level analysis.

Long-Term Effects of Aircraft Noise Exposure on Vascular Oxidative Stress, Endothelial Function and Blood Pressure: No Evidence for Adaptation or Tolerance Development

Transportation noise is recognized as an important cardiovascular risk factor. Key mechanisms are noise-triggered vascular inflammation and oxidative stress with subsequent endothelial dysfunction. Here, we test for adaptation or tolerance mechanisms in mice in response to chronic noise exposure. C57BL/6J mice were exposed to aircraft noise for 0, 4, 7, 14 and 28d at a mean sound pressure level of 72 dB(A) and peak levels of 85 dB(A). Chronic aircraft noise exposure up to 28d caused persistent endothelial dysfunction and elevation of blood pressure. Likewise, reactive oxygen species (ROS) formation as determined by dihydroethidium (DHE) staining and HPLC-based measurement of superoxide formation in the aorta/heart/brain was time-dependently increased by noise. Oxidative burst in the whole blood showed a maximum at 4d or 7d of noise exposure. Increased superoxide formation in the brain was mirrored by a downregulation of neuronal nitric oxide synthase (Nos3) and transcription factor Foxo3 genes, whereas Vcam1 mRNA, a marker for inflammation was upregulated in all noise exposure groups. Induction of a pronounced hearing loss in the mice was excluded by auditory brainstem response audiometry. Endothelial dysfunction and inflammation were present during the entire 28d of aircraft noise exposure. ROS formation gradually increases with ongoing exposure without significant adaptation or tolerance in mice in response to chronic noise stress at moderate levels. These data further illustrate health side effects of long-term noise exposure and further strengthen a consequent implementation of the WHO noise guidelines in order to prevent the development of noise-related future cardiovascular disease.

A meta-analysis of the first-night effect in healthy individuals for the full age spectrum

OBJECTIVES

The first-night effect (FNE) affects the accuracy of polysomnography (PSG) findings. However, the levels of FNE in different ages are unclear.

METHODS

We searched PubMed, Cochrane Library, Embase and Web of Science. The studies that reported sleep parameters by PSG for at least 2 consecutive nights from healthy individuals were included. The weighted mean differences were used to assess the effect size of differences in each sleep parameters between the first and second nights, as well as between the second and the third.

RESULTS

A total of 53 studies from 1422 subjects with mean age of 9.2-85.5 years were included. Meta-analyses showed that prolonged sleep onset latency, wake time after sleep onset and rapid eye movement sleep (REM) latency, accompanied by decreased total sleep time, sleep efficiency, and REM and increased non-rapid eye movement sleep stage 1 (N1) during the first night compared to the second (all P-value ≤ 0.001). No significant differences were observed in N2 and slow wave sleep, apnea-hypopnea index or periodic limb movement index (all P-value > 0.5). A non-linear association between FNE and age was observed: young adults (age 20-29 years) had the lowest level of FNE compared to other age ranges. Moreover, no significant differences were observed in most sleep parameters between the second and third night except more N2 and less REM in the second night (both P-value < 0.05).

CONCLUSIONS

The FNE exists in most cases but only in the first night of PSG recording and is less pronounced among young adults.

Impact of Noise Exposure on Risk of Developing Stress-Related Metabolic Effects: A Systematic Review and Meta-Analysis

Background

Exposure to noise can increase biological stress reactions, which may increase adverse health effects, including metabolic disorders; however, the certainty in the association between exposure to noise and metabolic outcomes has not been widely explored. The objective of this review is to evaluate the evidence between noise exposures and metabolic effects.

Materials and Methods

A systematic review of English and comparative studies available in PubMed, Cochrane Central, EMBASE, and CINAHL databases between January 1, 1980 and December 29, 2021 was performed. Risk of Bias of Nonrandomized Studies of Exposures was used to assess risk of bias of individual studies and certainty of the body of evidence for each outcome was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

Results

Fifty-six primary studies reporting on cortisol, cholesterol levels, waist circumference, glucose levels, and adrenaline and/or noradrenaline were identified. Although meta-analyses suggested that there may be an increase in waist circumference and adrenaline with increased noise exposure, the certainty in the evidence is very low. Overall, the certainty in the evidence of an effect of increased noise on all the outcomes were low to very low due to concerns with risk of bias, inconsistency across exposure sources, populations, and studies, and imprecision in the estimates of effects.

Conclusions

The certainty of the evidence of increased noise on metabolic effects was low to very low, which likely reflects the inability to compare across the totality of the evidence for each outcome. The findings from this review may be used to inform policies involving noise reduction and mitigation strategies, and to direct further research in areas that currently have limited evidence available.

Non-auditory effects of industrial chronic noise exposure on workers; change in salivary cortisol pattern

Background

Noise has different auditory and non-auditory effects on human. In noisy environments, noise as a non-specific stressor can activates the hypothalamic-pituitary-adrenal axis (HPA, cortisol). The aim of this study was to evaluate the effect of chronic exposure to noise on salivary cortisol on industrial workers.

Methods

This cross-sectional study had a case/control design. 136 male workers (68 workers were exposed to chronic industrial noise, and 68 other workers were exposed to background noise) voluntarily enrolled in the study. The equivalent noise level was measured at workstations and salivary cortisol for both case and control groups was measured at the beginning (6 AM) and also at the end of work shift (4 PM). The amount of change in the average of the values of the two groups were compared with each other.

Results

The measured Leq_8h (equivalent continuous sound level) in case and control groups were 87.43 dB-A and 67.6 dB-A, respectively. Comparison of salivary cortisol levels change in groups shows a significant differences in control groups for salivary cortisol in the morning and in the evening samples (p < 0.05); but not in the case group (p = 0.052). Also, comparison of salivary cortisol levels changes with noise exposure experience in the case subgroups revealed no significant difference (p > 0.05).

Conclusion

This study showed that chronic exposure to industrial noise can lead to a change in pattern of salivary cortisol secretion especially in the evening (at the end of the work shift), in a way that instead of its normal decrease, an increase happened.

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.

Noise exposure among teachers in technology educational shops in selected British Columbia, Canada, high schools

Teachers in technology education shops (TESs) in high schools are at risk from exposure to occupational hazards, including physical work demands and chemicals, particulate matter and noise, as well as non-optimal working conditions negatively affected by temperature, humidity, and lighting. This study evaluated the exposure to noise of 17 TES teachers working in 17 wood-working, metal-working, and automotive shops in selected high schools in British Columbia, Canada, and examined the quality of the acoustical teaching environments due to background noise. This study characterized noise control measures in the sampled TESs and observed the safety practices of teachers during TES classes. The results of this investigation indicated that almost 60% of the participating teachers were exposed to unacceptable levels of noise during teaching and working in TESs. It also showed that TES acoustical environmental quality was adversely affected by high background noise levels due to poor room designs and settings. Practical recommendations were provided to reduce and control the exposure to noise in TESs and to enhance the quality of health, safety, and quality of teaching environment in these TESs.

Multidimensional sleep quality of dependent self-employment workers

Background

The number of workers in non-standard employment (NSE) is increasing due to industrial change and technological development. Dependent self-employment (DSE), a type of NSE, was created decades ago. Despite the problems associated with this new type of employment, few studies have been conducted on the effects by DSE on health, especially sleep quality. This study aims to determine the relationship between DSE and sleep quality.

Methods

This study analyzed data of 50,250 wage workers from the fifth Korean Working Conditions Survey. Workers that did not respond or refused to answer any questions related to variables were excluded, and finally 36,709 participants were included in this study. A total of 2,287 workers (6.2%) were compared with non-DSE (34,422; 93.8%) workers, and multiple logistic regression analyses were applied.

Results

DSE status had a significant association with difficulty falling asleep (odds ratio [OR]: 1.331, 95% confidence interval [CI]: 1.178–1.504), difficulty maintaining sleep (OR: 1.279; 95% CI: 1.125–1.455), and extreme fatigue after waking up (OR: 1.331; 95% CI: 1.184–1.496). A multiple logistic regression of the variables for sleep quality in DSE showed a significant association with exposure to physical factors for all types of poor sleep quality as well as shift work for difficulty maintaining sleep with extreme fatigue after waking up. Long working hours and emotional labor were also associated with extreme fatigue after waking up.

Conclusions

This study shows a significant association between DSE and poor sleep quality, especially when workers were exposed to physical risk factors (noise, vibration, abnormal temperature, etc.) and shift work.

Analysis of Risk Factors in Occupational Accidents in Brazil: A Population-Based Study

OBJECTIVE

To investigate the association of occupational risks factors, including specific work characteristics with the occurrence of accidents at workplace and on the way to work in Brazil.

METHODS

We used a cross-sectional study design with comparison groups, to inquire data from 47,629 participants of the Brazilian National Health Survey. Logistic regression analysis was performed for distinct multivariate models.

RESULTS

Exposure to intense noise, biological materials, work experience of 40 years or more, and intense physical exertion were significantly associated with accidents at work. Regarding to accidents on the way to work, exposure to intense noise and performing work activities that require intense physical exertion remained associated.

CONCLUSION

This study contributes to highlight the effects of multiple work-related risk factors on the occurrence of occupational accidents at the workplace and on the way to work in Brazil.

Acute Effects of Air Pollution and Noise from Road Traffic in a Panel of Young Healthy Adults

Panel studies are an efficient means to assess short-term effects of air pollution and other time-varying environmental exposures. Repeated examinations of volunteers allow for an in-depth analysis of physiological responses supporting the biological interpretation of environmental impacts. Twenty-four healthy students walked for 1 h at a minimum of four separate occasions under each of the following four settings: along a busy road, along a busy road wearing ear plugs, in a park, and in a park but exposed to traffic noise (65 dB) through headphones. Particle mass (PM_2.5, PM₁), particle number, and noise levels were measured throughout each walk. Lung function and exhaled nitrogen oxide (NO) were measured before, immediately after, 1 h after, and approximately 24 h after each walk. Blood pressure and heart rate variability were measured every 15 min during each walk. Recorded air pollution levels were found to correlate with reduced lung function. The effects were clearly significant for end-expiratory flows and remained visible up to 24 h after exposure. While immediate increases in airway resistance could be interpreted as protective (muscular) responses to particulate air pollution, the persisting effects indicate an induced inflammatory reaction. Noise levels reduced systolic blood pressure and heart rate variability. Maybe due to the small sample size, no effects were visible per specific setting (road vs. park).

Irregular work schedule and sleep disturbance in occupational drivers-A nationwide cross-sectional study

BACKGROUND

The objective of this study was to investigate the relationship between irregular work schedules and sleep disturbance and compare the impacts of work schedule on sleep disturbance between occupational drivers and office workers.

METHODS

Using data from the 3rd and 4th Korean Working Conditions Survey, 3,070 occupational drivers and 9,898 office workers were included in this study. The subjects' days of night work, evening work, and subjective complaints of sleep disturbance were investigated along with other covariates.

RESULTS

In the multivariate logistic regression analyses, occupational drivers (odds ratio [OR], 95% confidence interval [CI]: 1.51, 1.11-2.05), workers who were engaged in more night work (2.49, 1.84-3.38 for 1-15 days, and 3.80, 2.67-5.41 for 16-30 days) and evening work (2.22, 1.66-2.97 for 1-15 days, and 1.76, 1.26-2.45) were more likely to report sleep disturbance. Moreover, occupational driving showed significant interaction effects with both night and evening work on sleep disturbance, and therefore, showed higher ORs for sleep disturbance in the 16-30 days night (5.38, 3.40-8.52) and evening (3.13, 1.97-4.98) compared to no night and evening working office workers.

CONCLUSIONS

Occupational drivers who are exposed to night work and evening work are at higher risks for sleep disturbance. Therefore, for the public and drivers' safety, optimal work schedules for minimising sleep disturbance should be developed.

Night noise exposure and risk of death by suicide in adults living in metropolitan areas

BACKGROUND

Noise is defined as "sound that is unwanted, unpleasant, or harmful to health." It may induce negative emotions and mental health problems and even may leads to increased suicide risk. Little attention has been paid so far to a potential link between noise and suicide. We investigated the association between nighttime environmental noise and suicide death in adults in the Republic of Korea.

METHODS

We analyzed the data from the National Health Insurance Service-National Sample Cohort, with a 4-year baseline (2002-2005) and an 8-year follow-up (2006-2013) assessment. A total of 155,492 adults constituted the study sample: younger adults (20-54 years, n = 124,994), or older adults (≥55 years, n = 30,498), and adults with mood and anxiety disorders (n = 34,615). Suicide death was defined as per International Classification of Diseases-10 code X60-X84. Data on nighttime noise were obtained from the National Noise Information System.

RESULTS

During the study period, 315 (0.2%) died of suicide. The incidence of suicide per 100,000 person-years was 25.71. With interquartile range increases in nighttime noise, the adjusted hazard ratio (HR) for suicide death was significantly increased: 1.32 (95% confidence interval [CI]: 1.02-1.70) for younger adults, 1.43 (95% CI: 1.01-2.02) for older adults, and 1.55 (95% CI: 1.10-2.19) for adults with mental illness. In the penalized regression spline models, the HRs for suicide death were gradually increased with environmental noise levels, and the risk was the highest for adults with mental illness.

CONCLUSIONS

We found a significant association between exposure to nighttime noise and the risk of suicide death in adults in the Republic of Korea.

Will daytime occupational noise exposures induce nighttime sleep disturbance?

BACKGROUND

Nighttime environmental noise affects sleep quality. However, the effects of daytime occupational noise remain unclear.

METHODS

A quasi-experiment of 48 participants who had been employed for at least six months in two hospital cafeterias. The participants were randomly designated to be assessed on high- and low-noise workdays for 8 h or low- and high-noise workdays, separated by a washout period of 14 days. Subsequently, pure tone audiometry, autonomic nervous system (ANS) function tests, serum cortisol tests, and polysomnography were conducted.

RESULTS

For the 40 participants in the study, the 8-h time-weighted average of personal noise exposed on high- and low-noise workdays was 76.8 dBA (standard deviation, SD: 6.2) and 61.0 dBA (SD: 7.1), respectively. Participants with higher personal noise exposure during the day were found to have a lower percentage of slow wave sleep (percent change of mean value: -1.287%; 95% CI: -2.602%, -0.037%) and lower sleep efficiency (-0.267%; 95% CI: -0.525%, -0.008%). In addition, after work, personal noise exposure was revealed to be related to increased serum cortisol levels (1.698%; 95% CI: 0.887%, 2.528%), and sympathetic activity as measured by low frequency/high frequency (3.000%; 95% CI: 1.294%, 4.706%) and blood pressures by cold pressor test (systolic: 5.163%; 95% CI: 2.780%, 7.537%) (diastolic: 3.109%; 95% CI: 1.604%, 4.614%).

CONCLUSIONS

Daytime occupational noise exposure had sustained effects on nighttime sleep quality, specifically on slow wave sleep and sleep efficiency. These disturbances could be partially explained by post-shift elevated cortisol and ANS activity. The psychosocial and metabolic consequences of poorer sleep quality induced by occupational noise exposure warrant further investigation.

Lifetime exposure to self-reported occupational noise and prevalent rheumatoid arthritis in the National Health and Nutrition Examination Survey (2011-2012)

Multiple risk factors for rheumatoid arthritis (RA) have been studied, but there is a dearth of research on occupational noise, which is highly prevalent in the United States (U.S.). This study aimed to determine whether occupational noise exposure was associated with an elevated risk of prevalent RA in the U.S. general population. Data from the 2011 to 2012 cross-sectional, population-based National Health and Nutrition Examination Survey were used for secondary analysis. Self-reported lifetime exposure to very loud noise was linked to self-reported doctor-diagnosed RA in a sample of 4192 participants. Weighted logistic regression was used to obtain nationally representative prevalence odds ratios (OR). The main and fully adjusted models yielded OR = 3.98 (95% CI: 1.74, 9.11) and OR = 2.84 (95% CI: 1.23, 6.57) for participants exposed for ≥ 15 years compared to never exposed participants. Excluding those diagnosed with RA more than five years before the interview, the effect dropped to OR = 3.67 (95% CI: 1.06, 12.75) in the main model, and was no longer significant in the fully adjusted model (OR = 2.68, 95% CI: 0.80, 8.96). The only significant effect modifier was race/ethnicity, with higher risk in Non-Hispanic whites. To conclude, long-term occupational noise exposure might be a modifiable risk factor for RA, but currently, the evidence base is very thin and tenuous.

Auditory closed-loop stimulation of EEG slow oscillations strengthens sleep and signs of its immune-supportive function

Sleep is essential for health. Slow wave sleep (SWS), the deepest sleep stage hallmarked by electroencephalographic slow oscillations (SOs), appears of particular relevance here. SWS is associated with a unique endocrine milieu comprising minimum cortisol and high aldosterone, growth hormone (GH), and prolactin levels, thereby presumably fostering efficient adaptive immune responses. Yet, whether SWS causes these changes is unclear. Here we enhance SOs in men by auditory closed-loop stimulation, i.e., by delivering tones in synchrony with endogenous SOs. Stimulation intensifies the hormonal milieu characterizing SWS (mainly by further reducing cortisol and increasing aldosterone levels) and reduces T and B cell counts, likely reflecting a redistribution of these cells to lymphoid tissues. GH remains unchanged. In conclusion, closed-loop stimulation of SOs is an easy-to-use tool for probing SWS functions, and might also bear the potential to ameliorate conditions like depression and aging, where disturbed sleep coalesces with specific hormonal and immunological dysregulations.

Circulating hormones undergo fluctuations during sleep. Here, the authors increase electroencephalographic slow oscillations (SO) during sleep in men using an auditory closed-loop stimulation, and show that the circulating level of cortisol, aldosterone and immune cell count can be altered.

The combined effect of cigarette smoking and occupational noise exposure on hearing loss: evidence from the Dongfeng-Tongji Cohort Study

Combined effect of cigarette smoking and occupational noise exposure on hearing loss has rarely been evaluated among Chinese population, especially among females. This cross-sectional study was conducted in 11196 participants of Dongfeng-Tongji cohort study. Smoking status was self-reported through questionnaire and occupational noise exposure was evaluated through workplace noise level and/or the job titles. Hearing loss was defined as a pure-tone mean of 25 dB or higher at 0.5, 1, 2, and 4 kHz in both ears. Compared with participants without occupational noise exposure, the risk of hearing loss was significantly higher for noise exposure duration ≥20 (OR = 1.45, 95%CI = 1.28–1.65). The association was particularly evident among individuals who were males (OR = 1.74, 95%CI = 1.45–2.08) and aged ≥ 70 (OR = 1.74, 95%CI = 1.30–2.33). Similarly, the risks increased with the increasing of pack-years in males and all age groups except for those aged <60. As to the combined effect, the hearing loss risk was highest for noise exposure duration ≥20 and pack-years ≥25 (OR = 2.41, 95%CI = 1.78–3.28), especially among males (OR = 2.42, 95%CI = 1.74–3.37) and those aged ≥70 (OR = 2.76, 95%CI = 1.36–5.60). Smoking may be an independent risk factor for hearing loss. And it may synergistically affect hearing when combined with occupational noise exposure, especially among males and older participants.

Evaluation of the effects of occupational noise exposure on serum aldosterone and potassium among industrial workers

The existing literature indicates that occupational exposure to noise may have adverse effects on workers' health. The aim of this study was to evaluate the possible effects of exposure to different sound pressure levels (SPLs) on serum aldosterone and potassium concentration among Iranian blue collar workers in Golgohar Mining and Industrial Company in Sirjan, Kerman Province, Iran. This case-control study was performed on 45 workers of Golgohar Mining and Industrial Company. The subjects consisted of 30 workers from manufacturing departments and 15 office employees of the mining company. The controls, mainly with administrative jobs were exposed to 72 dBA SPL. Cases, in two separate groups, were exposed to noise levels of 88 dBA and 103 dBA, respectively. Noise intensity was measured at the desired locations. Noise measurements were performed according to the International Organization for Standardization (ISO) 9612. To measure the serum aldosterone and potassium concentrations, a 5 mL blood sample was taken from each worker at the specified time intervals and aldosterone concentration was determined using enzyme-linked immunosorbent assay (ELISA) test in the laboratory. Repeated measurement and Spearman's correlation coefficient analysis were used with α = 0.05. Exposure to the different levels of sound pressure resulted in different aldosterone concentrations and meanwhile an increase in the SPL did not affect the concentration of potassium. From 10:00 AM to 10:30 AM, as SPL increased, aldosterone concentrations did not increase significantly but from 13:30 PM to 14:00 PM, raised SPL led to a significant increase in aldosterone concentration. However, there was no correlation between the concentration of potassium and different factors. This study indicated that increases in SPLs affect aldosterone concentration but at the same time do not have significant effects on serum potassium level.

Association between ambient noise exposure, hearing acuity, and risk of acute occupational injury

OBJECTIVE

This study aimed to examine the associations between acute workplace injury risk, ambient noise exposure, and hearing acuity, adjusting for reported hearing protection use.

METHODS

In a cohort of 9220 aluminum manufacturing workers studied over six years (33 300 person-years, 13 323 person-jobs), multivariate mixed effects models were used to estimate relative risk (RR) of all injuries as well as serious injuries by noise exposure category and hearing threshold level (HTL) adjusting for recognized and potential confounders.

RESULTS

Compared to noise <82 dBA, higher exposure was associated with elevated risk in a monotonic and statistically significant exposure-response pattern for all injuries and serious injuries with higher risk estimates observed for serious injuries [82-84.99 dBA: RR 1.26, 95% confidence interval (95% CI) 0.96-1.64; 85-87.99 dBA: RR 1.39, 95% CI 1.05-1.85; ≥88 dBA: RR 2.29, 95% CI 1.52-3.47]. Hearing loss was associated with increased risk for all injuries, but was not a significant predictor of risk for the subset of more serious injuries. Compared to those without hearing loss, workers with HTL ≥25 dB had 21% increased all injury risk (RR 1.21, 95% CI 1.09-1.33) while those with HTL 10-24.99 dB had 6% increased risk (RR 1.06, 95% CI 1.00-1.13). Reported hearing protection type did not predict injury risk.

CONCLUSION

Noise exposure levels as low as 85 dBA may increase workplace injury risk. HTL was associated with increased risk for all, but not the subset of serious, injuries. Additional study is needed both to confirm the observed associations and explore causal pathways.

Recent and long-term occupational noise exposure and salivary cortisol level

Environmental and occupational noise exposure have been related to increased risk of cardiovascular disease, hypothetically mediated by stress-activation of the hypothalamic-pituitary-adrenal (HPA) axis. The objective of this study was to investigate the relation between recent and long-term occupational noise exposure and cortisol level measured off work to assess a possible sustained HPA-axis effect. We included 501 industrial, finance, and service workers who were followed for 24h during work, leisure, and sleep. Ambient occupational noise exposure levels were recorded every 5s by personal dosimeters and we calculated the full-shift LAEq value and estimated duration and cumulative exposure based on their work histories since 1980. For 332 workers who kept a log-book on the use of hearing protection devices (HPD), we subtracted 10 dB from every noise recording obtained during HPD use and estimated the noise level at the ear. Salivary cortisol concentration was measured at 20.00 h, the following day at awakening, and 30 min after awakening on average 5, 14 and 14.5h after finishing work. The mean ambient noise exposure level was 79.9 dB(A) [range: 55.0-98.9] and the mean estimated level at the ear 77.7 dB(A) [range: 55.0-94.2]. In linear and mixed regression models that adjusted for age, sex, current smoking, heavy alcohol consumption, personal income, BMI, leisure-time noise exposure level, time since occupational noise exposure ceased, awakening time, and time of saliva sampling, we observed no statistically significant exposure response relation between recent, or long-term ambient occupational noise exposure level and any cortisol parameter off work. This was neither the case for recent noise level at the ear. To conclude, neither recent nor long-term occupational noise exposure levels were associated with increased cortisol level off work. Thus, our results do not indicate that a sustained activation of the HPA axis, as measured by cortisol, is involved in the causal pathway between occupational noise exposure and cardiovascular disease.

Do waking salivary cortisol levels correlate with anesthesiologist's job involvement?

Anesthetists' work carries great responsibility and can be very stressful. Cognitive appraisal plays a central role in stress responses; however, little is known about the relationship between stress appraisal and biological markers of stress, particularly among anesthesiologists. Stress response may be associated with increased levels of systemic cortisol, which can be conveniently measured in saliva and used as a marker for the extent of stress. The objective of this study was to examine the correlation between work-related cognitive variables and waking salivary cortisol, a possible stress marker, in anesthesiologists. Thirty-eight anesthesiologists were assessed for work-related thought intrusions and perceived "mental distance" between themselves and their work, using the pictorial representation of illness self-measure (PRISM), and underwent an implicit association test reflecting implicit job-stress associations. Salivary cortisol was measured twice upon awakening and an hour later, in saliva samples, using a kit based on chemoluminescence competition assay. Only implicit job-stress associations were correlated with waking cortisol (r = 0.35, p < 0.05). Furthermore, high implicit job-stress was related to elevated cortisol only among anesthesiologists reporting large "mental distance" from work, which may represent limited job involvement related to burnout. Anesthesiologists with a low degree of job involvement who have high implicit job-stress associations have higher levels of waking salivary cortisol. Further studies are necessary to assess the impact of stress management techniques on anesthesiologists' personal and professional behavior as well as on the quality of medical care.

The influence of hearing impairment on sleep quality among workers exposed to harmful noise

OBJECTIVE

To assess connections between sleeping quality and hearing impairment due to prolonged exposure to industrial noise.

DESIGN

Observational cross-sectional study.

SETTING

Occupational clinic of the Clalit Health Services in Israel.

PARTICIPANTS

298 male volunteers occupationally exposed to harmful noise, who had an audiometric examination performed by an occupational nurse as a part of the national workers health supervision programs.

MEASUREMENTS AND RESULTS

The participants underwent an audiometric testing, and their sleep quality was measured by a validated Mini Sleep Questionnaire (MSQ). Participants with hearing loss greater than 25 dBA in the range of 1000-4000 Hz were defined as the research group (n = 99) and were compared to those with no hearing impairment (n = 199). Sleeping disorders were age related (30% higher MSQ score among workers above 50 years, P = 0.003). Tinnitus was the highest sleep disturbing factor, with 75% higher score among those affected, P = 0.001. In multiple linear regression analysis, tinnitus was the leading sleep-disturbing factor (regression coefficient B = 8.66, P < 0.001) followed by hearing impairment (regression coefficient B = 2.42, P = 0.084), adjusted for age (or years of exposure) and coffee drinking. A part of the MSQ, related to insomnia, was further evaluated using logistic regression models. Tinnitus was again the leading sleep disturbing factor [OR = 11.91; CI95% (1.56-91.2)], followed by hearing impairment [OR = 3.051; CI95% (1.18-7.86)].

CONCLUSION

Although tinnitus was the main sleep disrupting factor, hearing impairment among workers occupationally exposed to harmful noise, independently contributed to sleep impairment, especially to insomnia, regardless of age and years of exposure.

Effects of audio stimulation on gastric myoelectrical activity and sympathovagal balance in healthy adolescents and adults

AIM

The primary aim of this study was to investigate the effects of different audio stimulations on gastric myoelectrical activity and sympathovagal balance in adolescents compared with adults.

METHODS

The study was performed in 11 adults and 12 adolescents. Each subject underwent two sessions, one for classical music, and the other for noise. Each session consisted of 30 min of baseline, 30 min of fasting audio stimulation, a test meal, 30 min of fed audio stimulation, and 30 min of recovery. Electrocardiogram and electrogastrogram were both recorded throughout each session.

RESULTS

(i) In the fasting state, both classical music and noise impaired gastric slow wave activity in adolescents. In adults, noise had no effects while classical music moderately improved slow wave rhythmicity. (ii) In the fed state, neither noise nor music had any effects on gastric slow waves. (iii) In the fasting state, both noise and music increased the sympathovagal balance in adolescents; in adults only noise had such an effect. (iv) The test meal increased the sympathovagal balance in all groups.

CONCLUSIONS

Gastric slow waves and the sympathovagal balance are more strongly affected by audio stimulation in adolescents than in adults. The test meal normalizes the audio stimulation-induced differences between the groups.

The effect of placebo administration on the first-night effect in healthy young volunteers

The first-night effect is a well-known phenomenon that is considered to result from a subject's lack of adaptation to the unfamiliar environment of a sleep laboratory and to the technical equipment used for polysomnography. The effect has been explored as a laboratory model for transient insomnia. The main characteristics of this effect are short total sleep time (TST) and rapid eye movement (REM) sleep, a lower sleep efficiency index, and longer REM sleep latency. Previous studies have reported that personality traits (such as trait anxiety) are a potential cause of the first-night effect and that the placebo effect is closely related to the anxiety levels of the subjects. To the best of our knowledge, there are no reports regarding the effects of a placebo on first-night sleep. This omission can be explained by the fact that the polysomnographic recordings obtained during the first night of a study are generally excluded from the analysis in order to avoid the inclusion of the first-night effect. In the present study, 8 male university students were subjected to polysomnographic examinations during drug-free, placebo-administration, and benzodiazepine-administration conditions in order to clarify the placebo effect on sleep during consecutive nights, particularly on the first night. The recordings for each condition were conducted for 4 consecutive nights. A placebo or 5 mg nitrazepam was administered at 2230 h using a double-blind crossover design, while no drug was administered during the drug-free condition. There was a 10-day interval between the examination of each condition. Polysomnographic recording was started at 2300 h and continued until the natural awakening of the subjects on the next morning. Subsequently, the subjects were requested to fill in a rating scale that is used to evaluate the subjective perception of sleep. An increase in stage-2 sleep associated with the first-night effect was observed on the first night during the drug-free and placebo-administration conditions. However, REM sleep reduction associated with the first-night effect was detected on the first night during the drug-free condition; this decrease in REM sleep was counteracted by the placebo during the placebo-administration condition. The nitrazepam, but not the placebo, decreased both slow-wave sleep (SWS) and REM sleep. The values for the tendency to fall asleep, feeling refreshed upon awakening in the morning, and the tension upon awakening in the morning were improved to a greater extent by the placebo and nitrazepam administrations than when no drug was administered. These results demonstrate the possibility that placebo administration may have a hypnotic/anxiolytic effect and may improve transient insomnia without causing SWS and REM sleep reductions.

Diazepam administration prevents testosterone decrease and lipofuscin accumulation in testis of mouse exposed to chronic noise stress

Lipofuscin is an autofluorescent and undegradable material, which accumulates in tissues during ageing and under different types of stress. Among these, oxidative stress represents a major trigger for lipofuscin formation. However, prolonged noise exposure is also an effective stressful stimuli. Diazepam may inhibit lipofuscinogenesis in liver and prevent the noise-induced reduction of the steroidogenesis in the adrenal gland. The aim of the study was to ascertain whether chronic noise exposure causes lipofuscin accumulation in mouse testis, and to evaluate the effects of diazepam administration. Eight-week old mice were either exposed for 6 weeks (6 h day(-1)) to white-noise (group A), or received diazepam (3 mg kg(-1), i.p.) before noise exposures (group B), while a further group was used as control (group C). Light fluorescence and transmission electron microscopy revealed lipofuscin in large amounts in the Leydig cells in mice of group A, which concomitantly had low serum testosterone levels; pre-treatment with diazepam occluded both effects. The present study indicates that: (i) chronic noise exposure causes lipofuscin accumulation at the level of the Leydig cells and a decrease in testosterone; (ii) all these effects are suppressed by pre-treatment with diazepam. As the Leydig cells represent the only cellular type of the interstitial testicular tissue having peripheral benzodiazepine receptors, these results could be explained by the capacity of the peripheral benzodiazepine receptors to prevent reactive oxygen species damage and to increase the resistance of these cells to oxidative stress.