Shiftwork and Biomarkers of Subclinical Cardiovascular Disease: The BCOPS Study

OBJECTIVE

To assess the association of shiftwork with biomarkers of subclinical cardiovascular disease and examine the moderating role of body mass index (BMI) in a police cohort.

METHODS

A cross-sectional analysis was conducted among officers who were categorized as working the day, evening, or night shift. Comparisons with inflammatory biomarkers were performed among shifts using analysis of variance/covariance and further stratified by BMI to assess potential effect modification.

RESULTS

Associations were observed between day and night shiftworkers for leukocytes, tumor necrosis factor alpha, and homocysteine. After BMI stratification, higher c-reactive protein (CRP) levels were observed among evening shiftworkers with a BMI more than or equal to 30 kg/m versus the day shift.

CONCLUSIONS

Future studies examining prospective changes in these markers will allow for more comprehensive evaluation of their association with shiftwork.

Bmal1 deletion in mice facilitates adaptation to disrupted light/dark conditions

Recently, by utilizing conventional and tamoxifen inducible Bmal1 (Brain and muscle Arnt-like protein 1) knockout mice, we found that delaying the loss of circadian rhythms to adulthood attenuates the impact on general integrity and survival at least under 12h light/12h dark conditions (LD). To understand further the contribution of Bmal1 in post-natal life under conditions of circadian disruption, we subjected inducible knockout mice (KO) and their littermate controls (Ctrl) to forced desynchrony protocols including cycles with non-24h periods, randomized light/dark cycles, and jet lag, and monitored their locomotor activity using radiotelemetry. Under these conditions, control mice cannot be entrained, as reflected by their maintenance of circadian behavior irrespective of schedules. By contrast, KO mice displayed higher activity levels in the dark phases of most cycles. Under a 3h light/3h dark regime, Ctrls displayed higher activity levels in the dark phases of all cycles although there were still obvious circadian rhythms, suggesting that an ultradian mechanism is also involved. Insulin sensitivity was markedly reduced by disrupted light schedules as expected in Ctrls, but not in the KOs. Thus, Bmal1 deletion in adult mice facilitates adaptation to new light/dark schedules and protects from insulin resistance induced by circadian disruption.

Stress and autonomic response to sleep deprivation in medical residents: A comparative cross-sectional study

The aim of this study was to evaluate the stress suffered by medical residents as the result of being on call for 24 hours, from a multidimensional approach. Two groups of medical residents selected according to their work shift, participated in the study: one group (n = 40) was sleep-deprived after having been actively on-call for 24 hours, and another contrast group (n = 18) had performed a normal work day and were not sleep-deprived. All participants completed pre-post measures during a 24 h cycle. These were administered on both occasions at 8 am. The measures included HRV, cortisol, cognitive performance and transitory mood. The effect of the group x phase interaction was significant for all variables analysed, indicating that doctors in the 24h on-call shift group showed significant deterioration in all physiological, performance and mood indicators in comparison with the participants in the group not on call. These results suggest the need to review medical on-call systems, in order to reduce the stress load, which has a direct effect on working conditions.

Anti-Müllerian hormone levels in nurses working night shifts

Our objective was to examine associations between night shift work and serum anti-Müllerian hormone (AMH) levels. We analyzed 1,537 blood samples from premenopausal female nurses in the Nurses' Health Study II, assayed for AMH. Rotating or permanent night shifts worked in the two weeks before blood collection and years of rotating night shift work were obtained via questionnaire. We found no associations between recent night shifts or rotating night shift work and AMH. The median difference in AMH was 0.3 (95% CI: -0.4, 0.8) ng/mL for ≥5 versus 0 recent night shifts and -0.1 (95% CI: -0.4, 0.3) ng/mL for ≥6 versus 0 years of rotating night shift work. Although we found no associations between night shift work and AMH, this does not preclude associations between night shift work and fertility operating through other mechanisms.

Working Time Society consensus statements: Individual differences in shift work tolerance and recommendations for research and practice

There is no standard definition of shift work universally, and no validated report of complete biological adjustment to shift work in workers. Similarly, the evidence for shift work tolerance is limited due to a small number of studies and a narrow range of outcome measures. This paper discusses evidence to date regarding individual differences in shift work tolerance and highlights areas for future research and recommendations for workplace practice. The few factors that are consistently associated with perceived or actual shift work tolerance are young age, low scores of morningness or being a late chronotype, low scores of languidity and neuroticism, high scores on extraversion, internal locus of control and flexibility and male sex. An important first step is to differentiate between factors that are potentially modifiable, such as those that are determined by lifestyle choices, and those factors specific to the working time arrangement. Identifying determinants of shift work tolerance and the ability to adjust to shift work, whether they are innate and/or acquired mechanisms, is important so workers who are less likely to tolerate shift work well can be self-identified and supported with appropriate harm/risk minimization strategies. This paper also identifies important areas for future research with the goal of increasing the evidence base on which we can develop evidence-based harm mitigation strategies for shift workers.

Working Time Society consensus statements: Evidence-based effects of shift work on physical and mental health

Potential effects of shift work on health are probably related to the misalignment between the light-dark cycle and the human activity-rest cycle. Light exposure at night mediates these effects, including social misalignment and leads to an inversion of activity and rest, which, in turn, is linked to changes in behaviours. This article reviews the epidemiological evidence on the association between shift work and health, and possible mechanisms underlying this association. First, evidence from findings of the meta-analyses and systematic reviews published in the last 10 yr is presented. In addition, it reports the larger single-occupation studies and recent large population-based studies of the general workforce. Koch's postulates were used to evaluate the evidence related to the development of disease as a result of exposure to shift work. Finally, we discussed limitations of the multiple pathways that link shift work with specific disorders and the methodological challenges facing shift work research. We concluded that the clearest indications of shift work being the cause of a disease are given when there is a substantial body of evidence from high quality field studies showing an association and there is good evidence from laboratory studies supporting a causal explanation of the link.

Working Time Society consensus statements: Evidence based interventions using light to improve circadian adaptation to working hours

Interventions and strategies to improve health through the management of circadian (re) adaptation have been explored in the field, and in both human and animal laboratory manipulations of shiftwork. As part of an initiative by the Working Time Society (WTS) and International Committee on Occupational Health (ICOH), this review summarises the literature on the management of circadian (re) adaption using bright light treatment. Recommendations to maximise circadian adaptation are summarised for practitioners based on a variety of shiftwork schedules. In slowly rotating night shift schedules bright light appears most suitable when used in connection with the first three night shifts. These interventions are improved when combined with orange glasses (to block blue-green light exposure) for the commute home. Non-shifting strategies involve a lower dosage of light at night and promoting natural daylight exposure during the day (also recommended for day shifts) in acordance with the phase and amplitude response curves to light in humans.

Working Time Society consensus statements: Circadian time structure impacts vulnerability to xenobiotics-relevance to industrial toxicology and nonstandard work schedules

The circadian time structure (CTS) has long been the subject of research in occupational medicine, but not to industrial toxicology, including methods of setting threshold limit values (TLVs) and employee biological monitoring. Numerous animal and human investigations document vulnerability to chemical, contagion, and other xenobiotics varies according to the circadian time of encounter. Permanent and rotating nightshift personnel are exposed to industrial contaminants in the same or higher concentration as dayshift personnel, and because of incomplete CTS adjustment to night work, contact with contaminants occurs during a different biological time than day workers. Thus, the amount of protection afforded by certain TLVs, especially for employees of high-risk settings who work night and other nonstandard shift schedules, might be inadequate. The CTS seems additionally germane to procedures of employee biological monitoring in that high-amplitude 24 h rhythms in biomarkers indicative of xenobiotic exposure may result in misjudgment of health risks when data are not gathered in sufficient frequency over time and properly interpreted. Biological reference values time-qualified for their rhythmic variation, currently of interest to laboratory medicine practice, are seemingly important to industrial medicine as circadian time and work-shift specific biological exposure indices to improve surveillance of personnel, particularly those working nonstandard shift schedules.

The Influence of Chronotype and Working Condition on Sleep Status and Health Related Quality of Life of Daytime Office Workers

Several companies in Japan introduced early working conditions (including recommendations on early morning work and prohibitions on nighttime overtime work) to decrease the number of long working hours at night. Nevertheless, individuals possess their own chronotype, i.e., their behavioral timing preference-be it morning or evening-that is associated with worker health. The purpose of this study was to investigate the influence of chronotype and working conditions on sleep and health related quality of life (HRQOL) using 126 daytime office workers who were classified as morning or evening type by their Morningness-Eveningness Questionnaire scores. We then compared morning and evening type workers' sleep variables (sleep onset/offset time and total sleep time), sleep quality (using the Japanese version of the Pittsburgh Sleep Quality Index), and HRQOL scores. Additionally, we compared the same sleep variables, sleep quality, and HRQOL scores of each chronotype category of worker under early and normal working conditions. As the results, evening type workers had late sleep onset/offset time, poor sleep quality, and low HRQOL (role-social component) compared to morning type workers. Furthermore, the evening type workers under early working conditions had earlier sleep onset/offset time and poorer sleep quality compared to those workers under normal working conditions. These results suggest that evening type workers in general have poor sleep and low HRQOL and those same workers under early working conditions, in particular, are associated with poor sleep quality. Therefore, in order to optimize worker health, we suggest that working conditions should be taken account of individual chronotypes.

Impact of work hours and sleep on well-being and burnout for physicians-in-training: the Resident Activity Tracker Evaluation Study

OBJECTIVE

The Resident Activity Tracker Evaluation (RATE) is a prospective observational study evaluating the impact of work hours, sleep and physical activity on resident well-being, burnout and job satisfaction.

BACKGROUND

Physician burnout is common and its incidence is increasing. The impact of work hours and sleep on resident well-being and burnout remains elusive. Activity trackers are an innovative tool for measuring sleep and physical activity.

METHODS

Residents were recruited from (i) general surgery and orthopaedics (SURG), (ii) internal medicine and neurology (MED) and (iii) anaesthesia and radiology (RCD). Groups 1 and 2 do not enforce restrictions on the duration of being on-call, and group 3 had restricted the duration of being on-call to 12 hours. Participants wore FitBit trackers for 14 days. Total hours worked, daily sleep, sleep on-call and daily steps were recorded. Participants completed validated surveys assessing self-reported well-being (Short-Form Health Survey), burnout (Maslach Burnout Inventory), and satisfaction with medicine.

RESULTS

Surgical residents worked the most hours per week, followed by medical and RCD residents (SURG, 84.3 hours, 95% CI, 80.2-88.5; MED, 69.2 hours, 95% CI, 65.3-73.2; RCD, 52.2 hours, 95% CI, 48.2-56.1; p < 0.001). Surgical residents obtained fewer hours of sleep per day (SURG, 5.9 hours, 95% CI, 5.5-6.3; MED, 6.9 hours, 95% CI, 6.5-7.3; RCD, 6.8 hours, 95% CI, 5.6-7.2; p < 0.001). Nearly two-thirds of participants (61%) scored high burnout on the Maslach depersonalisation subscore. Total steps per day and well-being, burnout and job satisfaction were comparable between groups. Total hours worked, daily sleep and steps per day did not predict burnout or well-being.

CONCLUSIONS

Work hours and average daily sleep did not affect burnout. Physical activity did not prevent burnout. Work hour restrictions may lead to increased sleep but may not affect resident burnout or well-being.

Rest and Activity Patterns of Army Aviators in Routine and Operational Training Environments

INTRODUCTION: Fatigue continues to be a leading cause of military aviation mishaps. Several factors, including reversed shift missions, can negatively affect sleep patterns and increase the risk of fatigue due to sleep restriction. Currently, there is a lack of objective data regarding the current rest and activity patterns of military aviators across multiple operational conditions. The purpose of this descriptive study was to document the rest and activity patterns of U.S. Army aviators in operational training and garrison (routine) environments using wrist-worn actigraphy devices.METHODS: Actigraphy data were collected from U.S. Army aviators in training (N = 20) and garrison (N = 77) environments for a period of 1 wk.RESULTS: Results from this study indicate that 90% of subjects in the training environment, even after accounting for small sleep bouts during the day, averaged less than the recommended 8 h of sleep daily across the recording week. Approximately half of subjects in garrison averaged less than 8 h of sleep daily after accounting for smaller sleep bouts. Sleep efficiency was relatively high and similar in both groups (∼84%). Subjects in the training group averaged significantly more time awake and less time sleeping than those in the routine garrison group. Moreover, subjects in training were exposed to more light during sleep than those in garrison.DISCUSSION: Training environments that are representative of deployed conditions restrict aviator restorative sleep. These results highlight the importance of continued research on aviator sleep and fatigue mitigation in operational environments.Bernhardt KA, Kelley AM, Feltman KA, Curry IP. Rest and activity patterns of Army aviators in routine and operational training environments. Aerosp Med Hum Perform. 2019; 90(1):48-52.

Causes and Management of Sleepiness Among Pilots in a Norwegian and an Austrian Air Ambulance Service-A Comparative Study

OBJECTIVE

We compared subjectively reported sleepiness and fatigue as well as causes and management strategies for combating sleepiness among pilots working in 2 different helicopter emergency medical services operating with different shift systems.

METHODS

Pilots from the Norwegian Air Ambulance (NAA) and Christophorus Flugrettungsverein (CFV) in Austria participated. NAA performs flight missions 24/7, whereas at the time of the study the participating CFV bases did not fly after sunset. The pilots are on duty for 1 week in both services. NAA and CFV used an identical research protocol, including questionnaires about sleep, sleepiness (Epworth Sleepiness Scale and Karolinska Sleepiness Scale), coping strategies, and work-related causes of fatigue.

RESULTS

CFV pilots kept busy, whereas NAA pilots slept and did physical exercise as strategies to prevent sleepiness. The majority in both groups used napping and coffee consumption as strategies. CFV pilots reported more frequently than NAA pilots that administrative duties and environmental factors were reasons preventing napping.

CONCLUSION

Some differences existed between the 2 pilot groups regarding strategies for managing sleepiness and causes that prevented pilots from napping. Pilots in both groups were healthy, physically active, and had normal Epworth Sleepiness Scale and Karolinska Sleepiness Scale scores.

Identifying shift worker chronotype: implications for health

Shift workers are at risk for developing serious health issues due to short sleep. One cause of short sleep is circadian misalignment: sleep time is not synchronized with the body's natural circadian rhythms. Although circadian rhythms are strongly driven by the light/dark cycle, humans have individualized sleep time preferences (chronotypes) based on genetics, development, and external influences. Evening chronotype individuals fall asleep later than average and have a higher risk for developing various noncommunicable diseases. What is unclear is the association between chronotype, shift work, and risks for acquiring chronic conditions. This review is focused on shift worker chronotype and associations with obesity. Because of the paucity of research, other health issues connected with circadian misalignment were included, allowing for a total of 21 research studies. Evidence from this review supports chronotype and certain health issues are associated with shift work, even after adjusting for short sleep duration. In addition, there is evidence to support future research on how shift worker chronotype matched with shift timing impacts worker health. Through better understanding of this interface, occupational health providers can provide more comprehensive worker education on the risks associated with shift work and sleep disturbances.

The impact of shift work and organisational climate on nurse health: a cross-sectional study

BACKGROUND

The negative effects of shift work schedules, specifically night and rotating shifts, have been widely reported. However, little is understood whether particular aspects of the organisational environment, related to specific shifts, may influence the negative impact of shift work. This study investigated the variation in organisational climate and health outcomes across shift work schedules (day, night, rotating).

METHODS

This cross-sectional study involved nursing staff (n = 108) who were all registered nurses from two Melbourne health services. There were slightly more nursing staff that participated from one health service (n = 56) than the other health service (n = 52). Nursing staff completed a survey on either paper form or online which comprised of: demographic characteristics, organisational climate (work environment scale) and health outcomes (general health questionnaire).

RESULTS

The study found that organisational climate factors and health outcomes differed across shift types. Rotating shift staff exhibited significantly higher coworker cohesion scores when compared to night staff. Night staff reported significantly greater levels of physical comfort within their work environment than rotating staff. Overall, supervisor support emerged as a significant predictor of health outcomes such as somatic complaints, social dysfunction and overall distress. Task orientation was also shown to significantly predict levels of social dysfunction.

CONCLUSIONS

Findings suggest that interventions with a focus on enhancing the organisational climate, focused in increasing supervisor support, may mitigate the potential negative health outcomes experienced by shift workers.

TRIAL REGISTRATION

Not applicable to this study.

Does modifying the timing of meal intake improve cardiovascular risk factors? Protocol of an Australian pilot intervention in night shift workers with abdominal obesity

INTRODUCTION

Shift work is an independent risk factor for cardiovascular disease (CVD). Shift workers who are awake overnight and sleep during the day are misaligned with their body's endogenous circadian rhythm. Eating at night contributes to this increased risk of CVD by forcing the body to actively break down and process nutrients at night. This pilot study aims to determine whether altering meal timing overnight, in a shift working population, will impact favourably on modifiable risk factors for CVD (postprandial bplasma lipids and glucose concentration).

METHODS AND ANALYSIS

A randomised cross-over study with two 4-week test periods, separated by a minimum of a 2-week washout will be undertaken. The effectiveness of redistributing energy intake overnight versus ad libitum eating patterns on CVD risk factors will be examined in night shift workers (n=20), using a standard acute test meal challenge protocol. Primary outcomes (postprandial lipids and glucose) will be compared between the two conditions: post-intervention and post-control period using analysis of variance. Potential effect size estimates to inform sample size calculations for a main trial will also be generated.

ETHICS AND DISSEMINATION

Ethics approval has been granted by the Monash University Human Research Ethics Committee (2017-8619-10329). Outcomes from this study will determine whether eliminating food intake for a defined period at night (1-6 am) impacts favourably on metabolic risk factors for CVD in night shift workers. Collective results from this novel trial will be disseminated through peer-reviewed journals, and national and international presentations. The results are essential to inform health promotion policies and guidelines for shift workers, especially those who aim to improve their metabolic health.

TRIAL REGISTRATION NUMBER

ACTRN12617000791336; Pre-results.

Shift work is associated with reduced heart rate variability among men but not women

BACKGROUND

Imbalance in the autonomic nervous system due to a disrupted circadian rhythm may be a cause of shift work-related cardiovascular diseases.

OBJECTIVE

We aimed to determine the association between shift work and cardiac autonomic activity in blue-collar workers.

METHODS

The study included 665 blue-collar workers aged 18-68 years in different occupations from two Danish cohort studies. Time and frequency domain parameters of heart rate variability (HRV) were measured during sleep using the Actiheart monitor, and used as markers of cardiac autonomic function. Multiple linear regression analyses were used to investigate differences in HRV between day and shift workers.

RESULTS

Shift workers had no significantly different HRV parameters than day workers, except for a lower VLF (B: 0.21; 95% CI: -0.36-0.05). The lower VLF was only present among non-night shift workers (p < 0.05) and not among night shift workers (p > 0.05). Results differed significantly by gender (p for interaction < 0.10): among men, shift work was negatively associated with RMSSD (B: -7.83; 95% CI: -14.28-1.38), SDNN (B: -7.0; 95% CI: -12.27-1.78), VLF (B: -0.27; 95% CI: -0.46-0.09) and Total Power (B: -0.61; 95% CI: -1.20-0.03), while among women, shift work was only associated with the LF/HF ratio (B: -0.29; 95% CI: -0.54-0.03).

CONCLUSION

Shift work was particularly associated with lower HRV during sleep among men. This indicates that shift work causes imbalance in the autonomic nervous system among men, which might increase their risk of cardiovascular diseases.

Associations between heat exposure, vigilance, and balance performance in summer tree fruit harvesters

BACKGROUND

We sought to evaluate potential mediators of the relationship between heat exposure and traumatic injuries in outdoor agricultural workers.

METHODS

Linear mixed models were used to estimate associations between maximum work-shift Wet Bulb Globe Temperature (WBGT_max) and post-shift vigilance (reaction time) and postural sway (total path length) in a cross-sectional sample of 46 Washington State tree fruit harvesters in August-September 2015.

RESULTS

The mean (SD) WBGT_max was 27.4 (3.2)°C in August and 21.2 (2.0)°C in September. The mean pre-work-shift participant urine specific gravity indicated minimal dehydration. Twenty-four percent of participants exhibited possible excessive sleepiness. There was no association between WBGT_max and post-shift reaction time or total path length.

CONCLUSIONS

Heat exposure was not associated with impaired vigilance or balance in this study, in which the overall mean (SD) WBGT_max was 25.9 (4.2)°C. However, the study identified opportunities to ensure adequate pre-work-shift hydration and to optimize sleep and work-shift timing in order to reduce occupational injury and heat-related illness risk.

Is one day off sufficient for re-adaptation to a daytime routine after two consecutive nights of work?

Fast rotation three-shift working schedules are common in the medical field in Taiwan. This study investigated whether 24 h off is sufficient for re-adaptation to a daytime routine after working two night shifts (NSs) by comparing changes in cognitive function, anxiety state and objectively measured sleep propensity between those working two NSs followed by 24 h off (n = 21, 2NS-off) and an off-duty group (n = 21, OD). The results showed that nurses in the 2NS-off group were less alert and had decreased visual attention performance and executive function ability than the OD group during the daytime. One day off appeared to be insufficient to adapt back to a daytime shift after two NSs. Further studies are warranted to investigate whether a longer sequence of consecutive NSs (e.g. four NSs) followed by two days off is suitable for a fast rotation three-shift work schedule to allow for optimal performance throughout the next daytime shift. Practitioner Summary: The medical field in Taiwan mandates at least 24 h off between night and day shifts, but this appears to be insufficient for re-adapting to a daytime shift after two night shifts. A longer sequence of consecutive night shifts followed by two days off may be more suitable.

Sleep on Long Haul Layovers and Pilot Fatigue at the Start of the Next Duty Period

INTRODUCTION

Layovers are critical for pilot recovery between flights and minimum layover durations are required by regulation. However, research on the factors affecting layover sleep and safety performance indicators (SPIs) before subsequent flights is relatively sparse. The present project combined data from 6 studies, including 8 long-range and 5 ultra-long range out-and-back trips across a range of different layover destinations (299 pilots in 4-person crews, 410 layovers, 1-3 d layover duration).

METHODS

Sleep was monitored via actigraphy from 3 d pre-trip to at least 3 d post-trip. Pilots rated their sleepiness (Karolinska Sleepiness Scale, KSS) and fatigue (Samn-Perelli scale, SP) at duty start for the inbound flight. Mixed model ANOVAs identified independent associations between fatigue and sleepiness SPIs and operational factors (domicile time of duty start for the inbound flight in six 4-h bins, layover duration, and total sleep time (TST) in the 24 h prior to inbound duty start).

RESULTS

TST was greatest on layovers ending between 1200-1559 domicile time (time in the city from which the outbound flight departed) and TST was a significant predictor of both KSS and SP ratings at duty start for the inbound flight.

DISCUSSION

TST in the 24 h prior to the inbound flight was greatest when duty start time allowed for the inclusion of a full domicile night time period. In this dataset, circadian end-time of layovers is a key determinant of pilot fatigue status at the beginning of the inbound duty period.Cosgrove J, Wu LJ, van den Berg M, Signal TL, Gander PH. Sleep on long haul layovers and pilot fatigue at the start of the next duty period. Aerosp Med Hum Perform. 2018; 89(1):19-25.

Restoration of resident sleep and wellness with block scheduling

CONTEXT

Block scheduling during residency is an innovative model in which in-patient and ambulatory rotations are separated. We hypothesised that this format may have a positive impact on resident sleep and wellness in comparison with a traditional format.

METHODS

We performed a single-centre, cross-sectional, observational study of residents rotating in the medical intensive care unit (MICU). Residents were observed for 4 weeks at a time: internal medicine (IM) residents were observed for 3 weeks in the MICU followed by 1 week in an ambulatory context, and non-IM residents were observed for 4 weeks in the MICU. We monitored daily total sleep time (TST) utilising actigraphy, and wellness measures with weekly Epworth Sleepiness Scale (ESS) and Perceived Stress Scale (PSS) questionnaires.

RESULTS

A total of 64 of 110 (58%) eligible residents participated; data for 49 of 110 (45%) were included in the final analysis. Mean ± standard deviation (SD) daily TST in the entire cohort was 6.53 ± 0.78 hours. Residents slept significantly longer during the ambulatory block than during the MICU block (mean ± SD TST 6.97 ± 1.00 hours and 6.43 ± 0.78 hours, respectively; p < 0.0005). Sleep duration during night call was significantly shorter than during day shift (mean ± SD TST 6.07 ± 1.16 hours and 6.50 ± 0.73 hours, respectively; p < 0.0005). A total of 390 of 490 (80%) ESS and PSS questionnaires were completed; scores significantly declined during rotations in the MICU. Internal medicine residents showed significant improvements in TST, and in ESS and PSS scores (p < 0.05) at the end of the ambulatory week. Non-IM residents, who remained in the MICU for a fourth week, continued a trend that showed a decline in perceived wellness.

CONCLUSIONS

Despite duty hour restrictions, residents obtain inadequate sleep. As MICU days accumulate, measures of resident wellness decline. Residents in a block schedule experienced improvements in all measured parameters during the ambulatory week, whereas residents in a traditional schedule continued a downward trend. Block scheduling may have the previously unrecognised benefits of repaying sleep debt, correcting circadian misalignment and improving wellness.

Long working hours as a risk factor for atrial fibrillation: a multi-cohort study

AIMS

Studies suggest that people who work long hours are at increased risk of stroke, but the association of long working hours with atrial fibrillation, the most common cardiac arrhythmia and a risk factor for stroke, is unknown. We examined the risk of atrial fibrillation in individuals working long hours (≥55 per week) and those working standard 35-40 h/week.

METHODS AND RESULTS

In this prospective multi-cohort study from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium, the study population was 85 494 working men and women (mean age 43.4 years) with no recorded atrial fibrillation. Working hours were assessed at study baseline (1991-2004). Mean follow-up for incident atrial fibrillation was 10 years and cases were defined using data on electrocardiograms, hospital records, drug reimbursement registers, and death certificates. We identified 1061 new cases of atrial fibrillation (10-year cumulative incidence 12.4 per 1000). After adjustment for age, sex and socioeconomic status, individuals working long hours had a 1.4-fold increased risk of atrial fibrillation compared with those working standard hours (hazard ratio = 1.42, 95% CI = 1.13-1.80, P = 0.003). There was no significant heterogeneity between the cohort-specific effect estimates (I2 = 0%, P = 0.66) and the finding remained after excluding participants with coronary heart disease or stroke at baseline or during the follow-up (N = 2006, hazard ratio = 1.36, 95% CI = 1.05-1.76, P = 0.0180). Adjustment for potential confounding factors, such as obesity, risky alcohol use and high blood pressure, had little impact on this association.

CONCLUSION

Individuals who worked long hours were more likely to develop atrial fibrillation than those working standard hours.