Longitudinal studies of sleep, physical activity and nutritional intake in shift workers: A scoping review

Impact of sleep disturbance in shift workers on hippocampal volume and psychomotor speed

STUDY OBJECTIVES

Shift work interferes with circadian rhythms, affecting sleep quality and cognitive function. Poor sleep quality in shift worker (SW)s can impair psychomotor performance due to fatigue and sleepiness, increasing the risk of errors, accidents, and reduced productivity. Given the potential for atrophic changes in the hippocampus due to sleep disturbances, our study investigates how poor sleep quality correlates with hippocampal structural alterations and impacts psychomotor performance among SWs.

METHODS

We recruited 100 SWs, classifying them based on sleep quality into two groups: good sleep-SW group (n = 59) and poor sleep-SW group (n = 41). Sleep quality was assessed using both 7-day actigraphy for sleep efficiency and the Pittsburgh Sleep Quality Index. A control group of 106 non-SWs without sleep problems (non-SW group) was also included for comparison. The outcome measures were psychomotor speed and hippocampal volumes, both total and by subfield.

RESULTS

The poor sleep-SW group showed significantly smaller hippocampal volumes than both the good sleep-SW group (p < .001) and the non-SW group (p = .003). Longer shift work years correlated with greater reductions in hippocampal volume in this group (r = -0.42, p = .009), unlike in the good sleep-SW group (r = 0.08, p = .541). Furthermore, they demonstrated declines in psychomotor speed relative to the non-SW group (p = .006), which correlated with smaller hippocampal volumes (r = 0.37, p = .020).

CONCLUSIONS

SWs with poor sleep quality exhibit significant hippocampal volume reductions and psychomotor speed decline, underscoring the importance of early intervention and support for sleep issues in this population.

Sleep duration and quality in permanent night work: an observational field study

PURPOSE

Permanent night workers conceivably show better adaptation of circadian rhythms to night work than shift workers and therefore better possibilities of obtaining sufficient sleep of good quality after night shifts. We investigated the effect of night shifts including number of consecutive shifts on sleep among self-selected permanent night workers, and studied if the effect of night shifts differed between morning and evening types and compared with 3-shift workers.

METHODS

The study population included 90 permanent night workers followed for 14 days (warehouse workers, 1228 observation days, 80% males). For comparison, we included 70 3-shift workers followed for 26 days (police officers, 1774 observation days, 100% men). Total sleep time (TST), primary sleep duration (PSD), and sleep efficiency were assessed by actigraphy. Measures of sleep quality and diurnal type were self-reported.

RESULTS

Among permanent night workers, TST, PSD, difficulties falling asleep, disturbed sleep, and the number of awakenings decreased after night shifts compared with days without night work. Sleep efficiency, difficulties awakening, and non-refreshing sleep increased. More consecutive night shifts were associated with shorter TST and PSD. Sleep outcomes did not differ by diurnal type. Permanent night workers had fewer awakenings after night shifts than 3-shift workers, but no other differences were observed.

CONCLUSION

This study does not provide evidence that supports recommendation of permanent night work to reduce adverse effects of night shifts on sleep. A limited number of consecutive night shifts is recommended to reduce accumulation of sleep debt.

Association between work-related factors and health behaviour clusters among Finnish private-sector service workers

PURPOSE

We examined how work-related factors associate with several health behaviours that appear together among the large, but less-studied, blue- and pink-collar worker group, which is characterized by low education and income levels.

METHODS

In 2019, we conducted a cross-sectional survey among private sector service workers (n = 5256) in Finland. We applied two-step cluster analysis to identify groups on the basis of leisure-time physical activity, sleep adequacy, frequency of heavy drinking, smoking status, and frequency of fruit, vegetable and berry consumption. We examined the associations with work-related factors, using multinomial regression analyses and adjusting for confounding factors.

RESULTS

We identified six clusters labelled as Moderately Healthy (28% of the participants), Healthy - Vigorous Exercise (19%), Sedentary Lifestyle (16%), Inadequate Sleep (15%), Mixed Health Behaviours (15%), and Multiple Risk Behaviours (8%). Those who perceived their work to be mentally or physically strenuous more commonly belonged to the Inadequate Sleep and Multiple Risk Behaviours clusters. Time pressure made belonging to the Inadequate Sleep, Mixed Health Behaviours, and Multiple Risk Behaviours clusters more likely. Those who were dissatisfied with their work more often belonged to the Healthy - Vigorous Exercise, Inadequate Sleep, and Multiple Risk Behaviours clusters.

CONCLUSION

In addition of finding several considerably differing health behaviour clusters, we also found that adverse working conditions were associated with clusters characterized by multiple risk behaviours, especially inadequate sleep. Private-sector service workers' working conditions should be improved so that they support sufficient recovery, and occupational health services should better identify co-occurring multiple risk behaviours.

Evidence summary on the non-pharmacological management of sleep disorders in shift workers

PURPOSE

This study aimed to evaluate, and integrate the relevant evidence on the non-pharmacological management of sleep disorders in shift workers to provide a reference for improving sleep of shift workers.

METHODS

According to the "6S" pyramid model of evidence, a comprehensive search was conducted in evidence-based databases, including BMJ-Best Practice, UpToDate, DynaMed, Cochrane Library, and Joanna Briggs Institute (JBI); clinical practice guideline websites, such as the Guidelines International Network; professional association websites, such as the World Sleep Society; and literature databases, including PubMed, Embase, CINAHL, China National Knowledge Infrastructure (CNKI), Wanfang Database, and Chinese Biology Medicine disc (CBM) from inception to November 30, 2022. Two researchers independently evaluated the literature in accordance with the evaluation standards; conducted the extraction, classification, and synthesis of the evidence; and evaluated its grade and recommendation grade.

RESULTS

A total of 18 studies were included, including 2 clinical decisions, 2 guidelines, 3 expert consensuses, and 11 systematic reviews. In total, 25 pieces of evidence were summarized from 6 aspects: sleep assessment, sleep scheduling, sleep hygiene, light therapy, workplace intervention, and other managements.

CONCLUSION

This study summarized the best evidence for the non-pharmacological management of sleep disorders in shift workers. Shift workers should reasonably arrange their sleep time and develop good sleep hygiene. Additionally, work organizations should jointly promote sleep to improve the sleep conditions of shift workers and promote their physical and mental health.

Differences in nutritional profile by chronotype among 12-h day shift and night shift nurses

Acute care nurses may suffer substantial fatigue if working night shift or if assigned a shift contrasting their preferred sleep-wake patterns, called chronotype. Nurses are at higher risk for diet-related, metabolic diseases compared to other healthcare professionals. Yet, the impact of preferred chronotype and mismatch to assigned shift on nutritional intake and risk for metabolic disease among acute care nurses is unclear. This observational study analyzed dietary data from 52 acute care nurses. Participants completed the revised morningness-eveningness questionnaire which gives a total score between 4 and 26. Lower scores (<12) were flagged as evening type (E-type), higher scores (>17) defined as morning type (M-type), and scores between 12 and 17 were categorized as neither types (N-type). N-type participants were considered chronotype matched when assigned to either shift, whereas E-types were only considered matched if assigned to night shift, and M-types matched only if assigned to day shift. Participants also recorded all dietary intake for 7 d (reflecting a typical workweek) in the MyFitnessPal phone application. Findings indicated that eveningness nurses had markers of MetS, including a significantly larger body mass index and waist circumference than N-types (p < 0.05). E-types also consumed, on average, more calories than other chronotypes (m = 1833.7 kcal), although this was not a statistically significant finding. Mismatched day (n = 7, 13.4%) and night (n = 5, 9.6%) nurses in our sample consumed, on average, more calories (m = 1935.1 kcal, m = 1981.2 kcal, respectively) than matched day (n = 24, 46.2%, m = 1642.6 kcal) or night (n = 16, 30.8%, m = 1599.1 kcal) nurses, although this finding was not statistically significant. Mismatched day nurses consumed significantly less fiber than day matched nurses (median = 10.9 g versus median = 18.5 g, p = 0.04), while night mismatched consumed significantly more fiber compared to night matched (median = 21 g versus median = 12.2 g, p = 0.05) nurses. Participant diets overall did not follow recommendations by the United States Department of Agriculture (USDA), who consumed a higher percentage of calories from saturated fats and a smaller percentage of calories from fiber, habits which increase risk for metabolic syndrome. Further research surrounding nutritional pathways utilizing larger samples is needed to uncover relationships with metabolic syndrome especially for eveningness-type nurses or if working a shift mismatched with preferred chronotype.

Physical and psychological health in intern paramedics commencing shift work: Protocol for an exploratory longitudinal study

BACKGROUND

Paramedics are routinely exposed to shift work. Existing research shows that shift work exposure is associated with adverse mental and physical health outcomes. However, the current understanding of the impact of commencing shift work in a paramedic role on health is limited. This can be addressed by recruiting new paramedics before they commence shift work, and conducting regular follow-ups of potential biological, psychological and social changes. The present study aimed to examine changes in biological, psychological and social factors relative to pre-shift work baseline in a cohort of paramedics commencing intern employment with an Australian ambulance service.

METHOD AND ANALYSIS

This observational, mixed-methods, longitudinal study aims to recruit 40 interns from one Australian ambulance service. Data collection will occur at baseline (standard day schedule for initial training), and subsequently at three months, six months, nine months and twelve months, to measure biological, psychological and social changes relative to baseline measurements. Changes in cardiometabolic markers (cholesterol, triglycerides, fasting glucose), microbiome (self-collected stool samples), sleep and physical activity (actigraphy) will be measured. Interns will also complete a battery of self-report questionnaires, sleep diaries and qualitative interviews to explore various psychological and social variables over time. Statistical analyses will be conducted using mixed effects regression, specifying a random effect of subject on the intercept, allowing participants to vary according to individual baseline levels, as well as tracking progress over time, appropriately accounting for serial correlation. Qualitative study components will be analysed via coding and thematic analysis procedures.

DISCUSSION

The present study protocol is a comprehensive outline of the observational study planned. The study will allow for greater knowledge of any changes in biological, psychological and social factors during a 12-month transition to shift work. The findings from the proposed study will have implications for the development of strategies to support early-career shift workers.

What do we know about the effect of night-shift work on cardiovascular risk factors? An umbrella review

Objective

To evaluate the existing evidence on the effect of night-shift work and its subtypes (permanent and rotating) on cardiovascular risk factors: diabetes, lipid disorders, being overweight, hypertension, smoking habits, sedentariness, and occupational psychosocial stressors.

Method

A Web of Sciences and Cochrane review library search was conducted to identify systematic reviews with or without meta-analysis dealing with the quantification of the link between night-shift work and the studied cardiovascular risk factors in working populations. We used the AMSTAR 2 to evaluate the quality of each review. The main results of the included systematic reviews were compiled in a summary structured around the different cardiovascular risk factors.

Results

After selection, 33 systematic reviews were included: nine for diabetes, four for lipid disorders, nine for being overweight, four for hypertension, two for smoking habits, three for occupational psychosocial stressors and two for sedentariness. The results confirmed an excess risk of diabetes of about 10% regardless of the type of night work. A stated excess risk of being overweight at around 25% was also highlighted for shift workers overall, which could reach 38% among night-shift workers. An increased risk of obesity, estimated at 5% for night-shift workers and at 18% for rotating shift workers, was observed. An excess risk of hypertension was estimated at around 30% when considering the broad definition of shift work and when night periods were included in rotating shifts. The literature provided inconsistent results for the link between lipid disorders and night-shift work. Shift workers appeared to be more likely to smoke. The link between shift work and occupational psychosocial stressors was scarcely explored in the available studies. Sedentariness was scarcely considered in systematic reviews, which prevents any firm conclusions.

Conclusion

The consequences of night work in terms of diabetes, being overweight/obesity and hypertension are established. Monitoring of these cardiovascular risk factors for these night-shift workers could be implemented by practitioners. In contrast, the links with lipid disorders, sedentariness, smoking habits, and occupational psychosocial stressors warrant further investigation.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021275212, PROSPERO (ID CRD42021275212).