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Introduction Although the metabolic health effects of shift work have been extensively studied, a systematic synthesis of the available research is lacking. This review aimed to systematically summarise the available evidence of longitudinal studies linking shift work with metabolic risk factors. Methods A systematic literature search was performed. Studies were included if (1) they had a longitudinal design; (2) shift work was studied as the exposure; and (3) the outcome involved a metabolic risk factor, including anthropometric, blood glucose, blood lipid, or blood pressure measures. Eligible studies were assessed for their methodologic quality. A best evidence synthesis consisting of three levels of evidence was used to draw conclusions per outcome: strong, moderate or insufficient evidence. Results Thirty-nine articles describing 22 studies were included. Strong evidence was found for a relation between shift work and increased body weight/BMI, risk for overweight, and impaired glucose tolerance. For the remaining outcomes (waist circumference, blood lipids, and blood pressure), there was insufficient evidence. Discussion Shift work seems to be associated with body weight gain, risk for overweight, and impaired glucose tolerance. Overall, lack of high–methodologic quality studies and inconsistency in findings led to insufficient evidence in assessing the relation between shift work and other metabolic risk factors. To strengthen the evidence, more high-quality longitudinal studies that provide more information on the shift work schedule (e.g., frequency of night shifts, duration in years) are needed. Further, research to the (mediating) role of lifestyle behaviours in the health effects of shift work is recommended, as this may offer potential for preventive strategies.

Introduction There is few research on the causal pathways in the link between obesity and work ability. Furthermore, there are indications that the effects of obesity on work ability differ for workers with different levels of physical workload. This study aimed to investigate the moderating effect of physical workload in the relation between obesity and work ability. Methods A longitudinal study was conducted among 36,435 Dutch construction workers who participated in at least two periodic medical examinations during the years 2008–2015. Logistic regression analyses were used to investigate the effect of manual material handling and strenuous work postures on the association between obesity and work ability. Confounding effects were tested for age, educational level, smoking, vigorous physical activity, psychosocial work demands, and working hours. Additive interaction between obesity and physical workload on work ability was tested using the relative excess risk due to interaction (RERI). Results Construction workers with overweight (OR=1.09; 95% CI: 1.02 to 1.16) or obesity (OR=1.27; 95% CI: 1.17 to 1.38) had an increased risk of poor/moderate work ability. Exposure to manual material handling (OR=1.58; 95% CI: 1.49 to 1.68) or strenuous work postures (OR=1.80; 95% CI: 1.70 to 1.90) also increased the risk of poor/moderate work ability. The effect of the combination of obesity with high physical workload was greater than the sum of the individual effects (strenuous work postures: RERI=0.39; 95% CI: 0.10 to 0.67; manual material handling: RERI=0.26; 95% CI: 0.02 to 0.51). Discussion Obesity and high physical workload were associated with poor work ability and had a synergistic, negative effect on work ability. To prevent poor work ability, there is a need for interventions that promote a healthy lifestyle and increase physical capacity, as well as for interventions that tailor physical workload to the individual physical capacity.

Introduction Shift work has been associated with cardiometabolic risk factors, but the relation is not clear for all risk factors, and the role of chronotype is largely unknown. We examined associations between shift work and cardiometabolic risk factors, and explored these associations in different chronotypes. Methods Risk factors (anthropometry, blood pressure, lipids, glucose, gamma-glutamyltransferase, C-reactive protein, uric acid, and glomerular filtration rate) were assessed among 7768 adults in 1987–1991, with repeated measurements every five years. In the ongoing 6th examination wave data on shift work history have been collected, with data from 2013–2015 being available. In 2016, linear mixed models and logistic generalised estimating equations were used to estimate associations between shift work and risk factors one year later. Results Shift workers had more often overweight (OR: 1.44, 95% CI: 1.06–1.95) and a higher body mass index (BMI) (β: 0.56 kg/m2, 95% CI: 0.10–1.03) than day workers. A significant difference in BMI between day and shift workers was observed among evening chronotypes (β: 0.97 kg/m2, 95% CI: 0.21–1.73), but not among morning chronotypes (β: 0.04 kg/m2, 95% CI: −0.85–0.93). No other significant associations between shift work and risk factors were found in the chronotype strata, except for glucose among intermediate chronotypes (β: −0.36, 95% CI: −0.62–0.11). No differences by frequency of night shifts and duration of shift work were observed. Conclusions Shift workers, in particular evening chronotypes, have a higher risk of overweight than day workers. More research is however needed to verify our results, and establish whether tailored interventions by chronotype are wanted.

Background Shift work may alter workers’ physical activity (PA) level, making PA a potential underlying mechanism of the negative health effects of shift work. As prior studies on shift work and PA have generally used self-reported, overall PA measures, the results may be susceptible to bias. Therefore, our aim was to compare objectively measured non-occupational and occupational PA levels between shift workers and non-shift workers. Methods Data were used from Klokwerk+, a prospective cohort study examining the health effects of shift work among health care workers. In total, 401 rotating and/or night shift workers and 78 non-shift workers were included, who wore Actigraph GT3X+ accelerometers for 7 consecutive days. Time spent sitting, standing, walking, running, stairclimbing, and cycling during leisure and at work was estimated using Acti4-software. Linear regression was used to compare proportions of time spent in these activities between shift and non-shift workers. Results Average accelerometer wear-time was 105.9 hours (SD=14.0) over an average of 6.9 days (SD=0.6). No differences between shift workers and non-shift workers were found in PA behaviours during leisure-time (p>0.05). At work, shift workers were less sedentary (B=−10.6 (95%-CI=−14.3- −6.8)) and spent larger proportions of the time standing (B=9.5 (95%-CI=6.4–12.6)) and walking (B=1.2 (95%-CI=0.1–2.2)) than non-shift workers. Conclusions Non-occupational PA levels of shift workers were similar to that of non-shift workers, but shift workers were more physically active (i.e. standing/walking) at work. Future research should focus on the role of this difference in occupational PA in the health effects of shift work.

Background Shift work is increasingly being suggested to be associated with an increased risk for overweight. Physical activity (PA) has been hypothesised to play a role in the health effects of shift work, but research on this role of PA is scarce. This study aimed to examine the association between night shift work and body mass index (BMI) and the moderating role of PA therein. Methods Data from 588 workers were used from the prospective cohort Klokwerk+ study, examining the health effects of night shift work in health care workers. BMI was calculated by measured body weight (in kg) divided by body height (in metre squared). PA was measured using the validated Short QUestionnaire to ASses Health-enhancing PA (SQUASH) questionnaire. Linear regression analyses were performed for the associations between shift work and BMI; interaction terms were added to determine the influence of PA. Results Mean BMI for shift workers was 25.3 (SD=4.2) versus 25.4 (SD=4.2) for non-shift workers (p>0.05). Shift workers were more moderately active than non-shift workers (beta 318 min/wk, 95% CI 141–496). After adjustment, there were no significant differences in the amount of vigorous intensity PA (beta-43 min/wk, 95% CI-115-26). There was no significant interaction for either moderate or vigorous PA in the shift work-BMI association. Conclusions Our study could not confirm the hypothesis that PA moderates the shift work-BMI relation. To confirm these findings and to get more insight into the moderating and mediating role of PA and other lifestyle behaviours, more longitudinal studies are recommended.