An industry-based cohort study of the association between weight gain and hypertension risk among rotating shift workers.

Objectives: We investigated whether the association between shift work and hypertension is independent of weight gain.

Methods: Subjects were 10,173 male employees (9209 daytime workers, 964 three-shift workers; mean follow-up period: 12.7 years). Hypertension was defined as systolic blood pressure 140 mm Hg or more or diastolic blood pressure 90 mm Hg or more. The risk of developing hypertension among shift workers was estimated using a Cox proportional hazards model with adjustment for several factors.

Results: Analysis revealed that "shift work" (hazard ratio [HR]: 1.85; 95% confidence interval [CI]: 1.68, 2.03), "baseline body mass index" (HR: 1.13; 95% CI: 1.12, 1.15), and "increase in body mass index during follow-up" (HR: 1.15; 95% CI: 1.13, 1.17) were significant independent risk factors for hypertension.

Conclusions: Shift work is a significant risk factor for hypertension that is independent of both starting weight and weight gained over years of work.