Nutrition/Obesity
Associations of night shift work with weight gain in female nurses in The Netherlands: results of a prospective cohort study Henriette M. van Duijne* Michael Schaapveld Henriette M. van Duijne Nina E. Berentzen Roel C.H. Vermeulen Jelle J. Vlaanderen Hans Kromhout Katarzyna Jóźwiak Anouk Pijpe Matti A. Rookus Flora E. van Leeuwen
Background: Working night shifts has been associated with increased risk of diabetes and cardiovascular disease, which may (partly) be explained by weight gain. We assessed associations of working night shifts and weight gain in the Nightingale Study.
Methods: This study included 36,273 (former) nurses, who completed questionnaires in 2011 and 2017. Night shift exposures (cumulative number (no.) nights, mean no. nights per month, consecutive no. nights per month) between 2007-2011 were categorized into tertiles. Poisson regression was used to estimate incidence rate ratio (IRR) of >5% weight gain among all participants and IRR of overweight/obesity (≥25 kg/m2) among women with healthy baseline BMI. Effect modification by age or menopausal status was assessed using likelihood-ratio (LR) tests.
Results: Working night shifts between 2007-2011 was not associated with >5% weight gain (IRR=1.04, 95% Confidence interval (CI)=0.97-1.12) compared to never working nights. However, the association between working nights and weight gain differed by menopausal status in 2011 (Pinteraction=0.040), with increased risk of gaining >5% weight (IRR=1.19, 95%CI=1.06-1.34) for postmenopausal women who worked nights compared to those who never worked nights. Postmenopausal women had increased risk of >5% weight gain when they worked ≥4 nights (IRR=1.26, 95%CI=1.05-1.51) or ≥4 consecutive nights (IRR=1.43, 95%CI=1.17-1.74) per month. Neither pre- nor postmenopausal women who worked nights had increased risk of overweight/obesity (IRR= 1.01, 95%CI=0.90-1.14 and IRR=1.22, 95%CI=0.99-1.49, respectively). However postmenopausal women who worked ≥241 nights (IRR=1.35, 95%CI=1.04-1.76) or ≥4 consecutive nights (IRR=1.38, 95%CI=1.07-1.77) had increased risk of overweight/obesity compared to those who never worked nights.
Conclusion: Working nights was associated with a slightly increased risk of weight gain and development of overweight/obesity for women who were postmenopausal at study inclusion.