Association between shift work and poor sleep quality in an Asian multi-ethnic working population: A cross-sectional study

Association between shift work and the risk of hypothyroidism in adult male workers in Korea: a cohort study

Background

Shift work has been reported to have several harmful effects on the human body. However, a small number of studies have evaluated the association between shift work and adverse effects on the thyroid. In our longitudinal study, we examined the causal association between shift work and the risk of hypothyroidism.

Methods

A Kangbuk Samsung Cohort Study was conducted on 112,648 men without thyroid disease at baseline who were followed up at least once between 2012 and 2019. Shift work status and shift schedule types were categorized using standardized questionnaires. Hypothyroidism was defined using the reference ranges of serum thyroid-stimulating hormones and free thyroxine levels. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident hypothyroidism were estimated using Cox proportional hazards regression analyses with the daytime work group as the reference.

Results

During the 501,237 person-years of follow-up, there were 6,306 incident cases of hypothyroidism (incidence density, 1.26 per 100 person-years). The multivariable-adjusted HR of incident hypothyroidism for the shift work total group that included all shifts compared with the daytime work group was 1.27 (95% CI: 1.15-1.40). For the fixed evening, fixed night, rotating shift, and other shift workers, the multivariable-adjusted HRs (95% CI) were 1.11 (0.76-1.61), 2.18 (1.20-3.93), 1.39 (1.23-1.56), and 1.00 (0.82-1.22), respectively. In subgroup analyses by age, the association between shift work and hypothyroidism was more pronounced in younger participants (< 40 years; HR: 1.31; 95% CI: 1.16-1.47).

Conclusions

Our large-scale cohort study showed an association between shift work and the incidence of hypothyroidism, especially in younger workers with night shifts.

Prevalence and associated factors of poor sleep quality among industrial workers in Addis Ababa, Ethiopia: findings from a cross-sectional study

OBJECTIVE

This study aimed to investigate the prevalence and associated factors of poor sleep quality among Bole Lemi Industrial Park workers in Addis Ababa, the capital of Ethiopia.

DESIGN

An institution-based cross-sectional study was conducted from July to August 2022. The data were collected using a validated and standardised Pittsburgh Sleep Quality Index Questionnaire. The collected data were entered into EpiData V.4.6 and analysed using Stata V.14. A multivariable binary logistic regression analysis was conducted to identify factors associated with poor sleep quality. The association was determined using an adjusted OR (AOR) with a 95% CI at a p value of <0.05.

SETTING

The study was conducted in Bole Lemi Industrial Park in Addis Ababa.

PARTICIPANTS

A total of 370 workers participated in this study.

OUTCOME MEASURES

The primary outcome of the study was the prevalence of poor sleep quality.

RESULTS

The total response rate was 87.7%. The majority (260, 70.3%) of the participants were female. The mean (±SD) age of the participants was 30.5 (±10.6) years. The prevalence of poor sleep quality during the last months was found to be 75.4% (n=279) (95% CI: 70.7% to 79.7%). Undiversified dietary intake (AOR: 1.63; 95% CI (1.09 to 2.78)), caffeine consumption more than 250 mg per day (AOR: 2.57; 95% CI (1.12 to 6.05)) and night shift work (AOR: 2.36; 95% CI (1.27 to 4.41)) were risk factors for poor sleep quality among sampled workers.

CONCLUSION

This study detected that poor sleep quality is highly prevalent among garment and textile industry workers, indicating that it is a significant public health issue that requires immediate attention. Therefore, modifications of the work environment involving night shift work and the improvement of workers' personal lifestyles involving dietary diversification and caffeine consumption are needed to minimise the burden of poor sleep quality among workers.

Toward precision sleep medicine: variations in sleep outcomes among disaggregated Asian Americans in the National Health Interview Survey (2006-2018)

STUDY OBJECTIVES

Asian Americans report higher rates of insufficient sleep than non-Hispanic Whites (NHWs). It is unclear how sleep outcomes differ among disaggregated Asian subgroups.

METHODS

The National Health Interview Survey (2006-2018) was used to analyze self-reported sleep duration and quality measures for Asian American subgroups (Chinese [n = 11,056], Asian Indian [n = 11,249], Filipino [n = 13,211], and other Asians [n = 21,767]). Outcomes included hours of sleep per day, the number of days reporting trouble falling asleep, staying asleep, waking up rested, and taking sleep medication in the past week. Subsetted multivariate logistic regression was used to assess factors impacting sleep outcomes by ethnicity.

RESULTS

29.2% of NHWs, 26.4% of Chinese, 24.5% of Asian Indians, and 38.4% of Filipinos reported insufficient sleep duration. Filipinos were less likely to report sufficient sleep duration (odds ratio 0.55, [confidence interval 95% 0.50-0.59]) and more likely to report trouble falling asleep (1.16 [1.01-1.33]) than NHWs. Chinese and Asian Indians had less trouble staying asleep (0.67 [0.58-0.77], 0.51 [0.44-0.59]) and falling asleep (0.77 [0.66-0.89], 0.72, [0.62-0.82]) than NHWs, and Asian Indians were more likely to wake feeling well rested (1.66 [1.48-1.87]). All Asian subgroups were less likely to report using sleep medications than NHWs. Foreign-born status had a negative association with sufficient sleep duration in Filipinos but a positive association in Asian Indians and Chinese.

CONCLUSIONS

Filipinos report the highest burden of poor sleep outcomes, and Asian Indians report significantly better sleep outcomes. These findings highlight the importance of disaggregating Asian ethnic subgroups to address their health needs.

CITATION

Wang RZ, Jamal A, Wang Z, et al. Toward precision sleep medicine: variations in sleep outcomes among disaggregated Asian Americans in the National Health Interview Survey (2006-2018). J Clin Sleep Med. 2023;19(7):1259-1270.

Acute sleep deprivation exacerbates systemic inflammation and psychiatry disorders through gut microbiota dysbiosis and disruption of circadian rhythms

Acute sleep deprivation (ASD) is often observed in shift workers and characterized by drowsiness and unrelenting exhaustion. The physiological and psychological effects of ASD include anxiety, depression, cognitive impairment, systemic inflammation, stress responses, and disruptions of gut microbiota. However, the mechanisms involved in the ASD-associated circadian dysregulations with regard to gut dysbiosis, systemic inflammation, physiological modulation, and psychiatry disorders remain unclear. The aim of this study was to investigate whether central nervous system disorders induced by ASD are related to inflammation, barrier dysfunction, and circadian dysregulation. We also assessed impacts on microbiota succession. Male C57BL/6 mice were randomly allocated to the control and sleep deprivation (SD) groups. Mice in the SD group were subjected to 72 h of paradoxical SD using the modified multiple-platform method for ASD induction (72 h rapid eye movement-SD). The effects of ASD on dietary consumption, behaviors, cytokines, microbiota, and functional genes were determined. The appetite of the SD group was significantly higher than that of the control group, but the body weight was significantly lower than that of the control group. The anxiety-like behaviors were found in the SD group. Alpha and beta diversity of microbiota showed significant decrease after ASD induction; the relative abundance of Candidatus_Arthromitus and Enterobacter was increased, whereas that abundance of Lactobacillus, Muribaculum, Monoglobus, Parasutterella, and others was decreased in the SD group. These effects were accompanied by reduction in fecal propionic acid. In the proximal colon, the SD group exhibited significantly higher inflammation (tumor necrosis factor-α [TNF-α]) and dysregulation of the circadian rhythms (brain and muscle ARNT-like 1 [BMAL1] and cryptochrome circadian regulator 1 [CRY1]) and tight junction genes (occludin [OCLN]) than the control group. Gut barrier dysfunction slightly increased the plasma concentration of lipopolysaccharide and significantly elevated TNF-α. Inflammatory signals might be transduced through the brain via TNF receptor superfamily member 1 A (TNFRSF1A), which significantly increased the levels of microglia activation marker (ionized calcium-binding adapter molecule 1 [IBA1]) and chemokine (intercellular adhesion molecule 1 [ICAM1]) in the cerebral cortex. The serotonin receptor (5-hydroxytryptamine 1A receptor [5-HT_1AR]) was significantly downregulated in the hippocampus. In summary, 72 h of rapid eye movement-SD induced physiological and psychological stress, which led to disruption of the circadian rhythms and gut microbiota dysbiosis; these effects were related to decrement of short chain fatty acids, gut inflammation, and hyperpermeability. The microbiota may be utilized as preventive and therapeutic strategies for ASD from the perspectives of medicine and nutrition.

Effect of chronic sleep deprivation on acrosomal integrity and functional parameters of murine sperm

OBJECTIVE

To evaluate the effect of chronic sleep deprivation on sperm function quality in mice.

DESIGN

Experimental study.

SETTING

Not applicable.

ANIMALS

Spermatozoa from twenty-four 10-week-old C57BL/6J male mice.

INTERVENTION(S)

The sleep deprivation group underwent gentle handling for 6 hours for 5 consecutive days. The mice in the sleep recovery group were allowed to sleep during the 24-hour period after the sleep deprivation protocol.

MAIN OUTCOME MEASURE(S)

After euthanasia, the spermatozoa were collected for analysis. Sperm motility was evaluated using computer-assisted sperm analyzer. Intracellular superoxide anion (O₂^-) activity, acrosome integrity, mitochondrial activity, and DNA fragmentation assays were conducted afterward.

RESULT(S)

Sleep deprivation and sleep recovery groups presented a lower percentage of spermatozoa with an intact acrosome, compared with the respective control groups. Regarding DNA fragmentation, a decreased proportion of spermatozoa with Comet I class intact DNA was observed in the sleep recovery group, compared with the recovery control group. Beat cross frequency was increased in the sleep recovery group.

CONCLUSION(S)

Sleep deprivation can reduce sperm quality, impairing acrosome integrity. Sleep recovery decreased DNA integrity and increased beat cross frequency.

Association between Shift Work Schedules and Cardiovascular Events in a Multi-Ethnic Cohort

BACKGROUND

Shift work is known to increase the risk of cardiometabolic diseases and mortality. We investigate the relationship between shift work schedules and cardiometabolic risk factors (smoking, hypertension, and obesity) and their association with cardiometabolic diseases (diabetes and cardiovascular diseases) in a multi-ethnic population from Singapore.

METHODS

2469 participants from the Singapore-based Multi-Ethnic Cohort underwent physical and clinical assessments. Shift work schedules (morning, evening, night, and mixed) were assessed using a validated questionnaire.

RESULTS

Among shift workers, night shift workers had a significantly higher prevalence of smoking (54.5%), diabetes (27.3%), and cardiovascular events (14.1%). Compared to non-shift workers, workers in the night (OR = 2.10, 95%CI: 1.26-3.41) and mixed (OR = 1.74, 95%CI: 1.22-2.48) shift groups were more likely to be current smokers. A significant association between shift duration and smoking (OR = 1.02, 95%CI: 1.00-1.03) was also observed, with longer shift duration (in years) leading to an increase in smoking behavior. No significant associations were found between shift work schedules and hypertension, obesity (BMI), diabetes, and cardiovascular disease, as well as other cardiometabolic risk factors and diseases.

CONCLUSION

This study found that shift schedules and shift duration were most strongly associated with smoking status after covariate adjustments (age, gender, ethnicity, socioeconomic status, and work arrangement), with night and mixed shift types being strongly associated with current smoker status. As smoking is a modifiable risk factor for cardiometabolic disease, employers of shift workers should increase work-based health interventions to control smoking and promote a healthier workforce.

Sleep disorders and work-related stress with oral hygiene among Indian shift workers

Construction workers are mostly migrants from isolated villages and are not vigilant about health care measures besides poor language skills. Majority of the population works in shifts across the globe. As a result of poor sleep architecture, excessive sleepiness or insomnia, the construction labourers working in shifts have approximately twice the risk of OSA when compared with those working in the daytime. Likewise, the performance and the productivity of employees in construction sites are impeded by added stress. Therefore, it is of interest to investigate the sleep disorders, work-related stress and its impact on oral hygiene among the construction workers in Chennai. A cross sectional study was conducted among 518 workers in various construction sites at Chennai, South India. The study incorporated BerlinQuestionnaire to evaluate disordered breathing during sleep, the Work Ability Index that contains questions concerning work, working ability and health and the Oral Hygiene Index Simplified (Greene and Vermillion, 1964) that was used for recording the oral hygiene status. Pearson correlation between education and OHI-S was statistically significant (r=-0.108). Multiple linear regression analysis revealed that mean WAI score had a positive significant association with work experience (B=0.059, SE=0.030, p=0.05), habits (B=0.032, SE=0.017, p=0.05) and marital status (B=0.135, SE=0.54, p=0.01). In contrast, education (B=-0.0.052, SE=0.023, p=0.02) and work schedule (B=0.022, SE=0.037, p=0.54) were inversely associated with the mean score. Based on the current findings, it is imperative to restore work ability for those with poor work ability thereby enhancing productivity in the migrant workers. As shift work may be extremely detrimental to poor sleep quality, the employers should arrange shift schedules in accordance with sleep physiology. Additionally, dental awareness and interventions are required to improve oral hygiene among migrant workers.

Different levels of circadian (de)synchrony -- where does it hurt?

A network of cellular timers ensures the maintenance of homeostasis by temporal modulation of physiological processes across the day. These so-called circadian clocks are synchronized to geophysical time by external time cues (or zeitgebers). In modern societies, natural environmental cycles are disrupted by artificial lighting, around-the-clock availability of food or shift work. Such contradictory zeitgeber input promotes chronodisruption, i.e., the perturbation of internal circadian rhythms, resulting in adverse health outcomes. While this phenomenon is well described, it is still poorly understood at which level of organization perturbed rhythms impact on health and wellbeing. In this review, we discuss different levels of chronodisruption and what is known about their health effects. We summarize the results of disrupted phase coherence between external and internal time vs. misalignment of tissue clocks amongst each other, i.e., internal desynchrony. Last, phase incoherence can also occur at the tissue level itself. Here, alterations in phase coordination can emerge between cellular clocks of the same tissue or between different clock genes within the single cell. A better understanding of the mechanisms of circadian misalignment and its effects on physiology will help to find effective tools to prevent or treat disorders arising from modern-day chronodisruptive environments.

Which Shiftwork Pattern Is the Strongest Predictor for Poor Sleep Quality in Nurses?

Shiftwork is related to an increased risk of several diseases, including gastric ulcers, myocardial infarction, and diabetes. Several shiftwork patterns are related to poor sleep quality, such as a quick returns or extended shifts. This study aimed to find the shiftwork patterns strongly associated with poor sleep quality amongst nurses. A cross-sectional analytical study was conducted among nurses working for at least one month. The sub-groups were the good sleep quality group (n = 150) and the poor sleep quality group (n = 472). Eligible participants were asked to complete a self-reported questionnaire comprising personal characteristics, job characteristics, shiftwork characteristics, and sleep quality. Factors associated with poor sleep quality were determined using logistic regression analysis. Two factors associated with poor sleep quality remained in the final model: viz., depression and backward rotational shift. The only independent factor for poor sleep quality was a backward rotational shift with an adjusted odds ratio (95% CI) of 1.946 (1.344, 2.871). In conclusion, compared with other shift patterns, backward shiftwork was the most significant factor associated with poor sleep quality and should be avoided.

Association between insomnia and constipation: A multicenter 3-year cross-sectional study using shift workers’ health check-up data

Background

Although insomnia and constipation are highly prevalent worldwide, studies examining a possible association between them are lacking. We examined the relationship between insomnia and constipation in shift workers who have a high prevalence of insomnia and other diseases.

Methods

This study had a multicenter cross-sectional design and conducted using health examination data including self-reported questionnaires. In total, 12,879 and 4,650 shift workers were enrolled in Severance Hospital and Wonju Severance Hospital, respectively, during 2015-2017. Multivariate logistic regression models and subgroup analysis were performed in each center with the same protocol, using a common data model.

Results

The mean age of the total population was 44.35 (standard deviation = 8.75); the proportion of males was 56.9%. Female sex, being underweight and non-smoker were strongly associated with an increased risk of constipation symptom (p < 0.001). Pooled odds ratios (ORs) were calculated using ORs of both centers with weights; there was a significant dose–response relationship (sub-threshold 1.76 [95% confidence interval [CI] 1.62–1.91]; moderate 2.28 [95% CI 2.01–2.60]; severe 4.15 [95% CI 3.18–5.41] in the final model, p for trend < 0.001). Subgroup analysis performed by stratifying sex and pooled ORs showed a similar trend to that of the entire group.

Conclusion

We observed a strong correlation between insomnia and constipation in this population. Our findings may help in formulating guidelines and policies to improve quality of life in shift workers through the management of sleep quality and proper bowel function. This study is the first to report this relationship among people working in shifts.

Influence of rotating shifts and fixed night shifts on sleep quality of nurses of different ages: a systematic literature review and meta-analysis

The objective of this study was to understand the influence of rotating shifts and fixed night shifts on the sleep quality of nurses using a systematic literature review and meta-analysis and to determine whether the sleep quality of nurses working rotating shifts or fixed night shifts differs from that of nurses working fixed day shifts. We conducted a meta-analysis on literature that had used the Pittsburgh Sleep Quality Index (PSQI) to gauge sleep quality and had been published between 2000 and 2020 in the Cochrane Library, CINAHL, MEDLINE, and PubMed databases. This study was conducted in accordance with PRISMA, and the quality of the literature was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross Sectional Studies. CMA 3.0 was employed for data analysis, and meta-regression analysis was conducted to examine the differences between the PSQI scores of nurses working fixed day shifts and those working rotating shifts or fixed night shifts. Following assessment, a total of 29 papers (34 items of data) were analyzed. The papers included a total of 3,935 nurses who worked fixed day shifts, 3,777 nurses who worked rotating shifts, and 1,559 nurses who worked fixed night shifts. Our subgroup analysis indicated that the sleep quality of nurses working rotating shifts was poorer than the sleep quality of nurses working fixed day shifts; the standardized mean difference (SMD) was 0.38 (95% CI: 0.24-0.52, p< .001), and the meta-regression analysis found that the difference in sleep quality between nurses over 40 years old working rotating shifts and those working fixed day shifts was significantly smaller than the difference in sleep quality between nurses 40 years old or younger working rotating shifts and those working fixed day shifts (β = -0.368, p= .011). The sleep quality of nurses working fixed night shifts was also poorer than the sleep quality of nurses working fixed day shifts; the SMD was 0.58 (95% CI: 0.38-0.78, p< .001), and the meta-regression analysis revealed that the difference in sleep quality between nurses over 40 years old working fixed night shifts and those working fixed day shifts was not significantly different from the difference in sleep quality between nurses 40 years old or younger working fixed night shifts and those working fixed day shifts (β = -0.118, p= .608). This meta-analysis found that both nurses working rotating shifts and those working fixed night shifts had poorer sleep quality than those working fixed day shifts and that age influenced the difference in sleep quality only between nurses working rotating shifts and those working fixed day shifts; the difference in sleep quality between nurses 40 years old or younger working rotating shifts and those working fixed day shifts was greater than the difference in sleep quality between nurses over 40 years old working rotating shifts and those working fixed day shifts.

Discrimination and Sleep among Asians and Pacific Islanders Adults

STUDY OBJECTIVES

To examine the association between discrimination and sleep duration and difficulty among Asians and Pacific Islanders (APIs) in the United States, and to test nativity and ethnic identity (EI) as effect modifiers.

METHODS

This cross-sectional study of 1,765 adults from the National Epidemiology Study of Alcohol and Related Conditions III, assessed discrimination using the Experiences of Discrimination scale. Discrimimation was classified as low, moderate, and high. Regression models were used to examine self-reported sleep duration and difficulty.

RESULTS

In bivariate analyses, individuals with high discrimination had the shortest sleep and reported sleep difficulty most often. Using linear models adjusted for sociodemographic and health characteristics, moderate and high discrimination were associated with 9 minutes (standard error [SE]: 4.8, p <0.10) and 14.4 minutes (SE: 6.0, p <0.05) less sleep, respectively, relative to low discrimination. Individuals with moderate and high discrimination had higher prevalence of sleep difficulty compared to those with low discrimination (prevalence ratio [PR]: 1.51, 95% confidence interval [CI]: 1.14-1.99 and PR: 1.73, 95% CI: 1.33-2.24, respectively). Interaction effect was observed in sleep difficulty by nativity and EI, but not duration. The association between discrimination and sleep difficulty was stronger among US-born relative to foreign-born participants. Among participants with low EI, moderate and high discrimination were associated with sleep difficulty, whereas among those with high EI, only high discrimination displayed this association.

CONCLUSIONS

Discrimination is associated with sleep duration and difficulty, and varies by nativity and EI. Research is needed to improve sleep among APIs that experience discrimination.[.