Shift work schedule and night work load: Effects on body mass index – a four-year longitudinal study

Objectives The aim of this study was to investigate changes in body mass index (BMI) between different work schedules and different average number of yearly night shifts over a four-year follow-up period. Methods A prospective study of Norwegian nurses (N=2965) with different work schedules was conducted: day only, two-shift rotation (day and evening shifts), three-shift rotation (day, evening and night shifts), night only, those who changed towards night shifts, and those who changed away from schedules containing night shifts. Paired student’s t-tests were used to evaluate within subgroup changes in BMI. Multiple linear regression analysis was used to evaluate between groups effects on BMI when adjusting for BMI at baseline, sex, age, marital status, children living at home, and years since graduation. The same regression model was used to evaluate the effect of average number of yearly night shifts on BMI change. Results We found that night workers [mean difference (MD) 1.30 (95% CI 0.70–1.90)], two shift workers [MD 0.48 (95% CI 0.20–0.75)], three shift workers [MD 0.46 (95% CI 0.30–0.62)], and those who changed work schedule away from [MD 0.57 (95% CI 0.17–0.84)] or towards night work [MD 0.63 (95% CI 0.20–1.05)] all had significant BMI gain (Pby Buchvold HV, Pallesen S, Waage S, Bjorvatn B. doi:10.5271/sjweh.3701

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