Objectives Triggered by disturbed circadian rhythm, increased blood pressure comprises an intermediate step on suggested pathways between shift work and cardiovascular disease. Despite accumulated evidence indicating an excess risk for cardiovascular disease among shift workers, studies on shift work and hypertension are inconclusive. Thus, we investigated the association between shift work and hypertension in German car manufacturing workers.

Method Baseline blood pressure and potential confounders for 25343 workers aged 16 to 64 years were obtained from standardised medical check-ups. Workers were analysed according to four exposure categories: no shift work, shift work without night shifts, shift work with night shifts and constant night shifts. Cross-sectional associations between shift work and hypertension were analysed using logistic regression adjusted for confounders and sets of behavioural, psychosocial and physiological factors.

Results Hypertension prevalence was highest among shift workers not working night shifts (11.5%), and lowest among workers not working shifts (7.8%). Unadjusted, a significant positive association with hypertension was found for shift work without night shifts (OR 1.53 95% CI 1.40–1.68) and constant night shifts (OR 1.46, 95% CI 1.29–1.65). Adjusted for confounders, only shift work without night shifts showed an increased hypertension risk (OR 1.15, 95% CI 1.02–1.30). However, stratification for occupational status suggested this excess risk to be attributable only to white-collar shift workers not working night shifts (OR 1.52 95% CI 1.22–1.88). After adjustments for behavioural factors no shift work category showed increased hypertension risks.

Conclusions Shift workers’ increased hypertension risk might be explained by behavioural risk factors, possibly triggered by disturbed circadian rhythm.