Night shift work and blood pressure: focusing on exposure doses

Abstract Objective: to determine whether levels of night work exposure (current dose; accumulated dose) are associated with hypertension (HBP), systolic blood pressure (SBP) and diastolic blood pressure (DBP). Methods: cross-sectional study of 893 nursing personnel. We collected data on sociodemographic, work-related and health behaviour factors and measured blood pressure using a digital monitor. Results: after adjusting for sociodemographic variables, working >4 nights per fortnight was associated with increased SBP (4.0 mmHg; 95% CI: 1.01; 6.97) and DBP (2.3 mmHg; 95% CI: 0.24; 4.35). Working more than four nights per fortnight was associated to hypertension (OR 1.57; 95% CI 1.01; 2.43). Individuals who worked at night for >9 years displayed, on average, higher blood pressure levels (SBP of 3.7 mmHg [95% CI: 1.49; 5.92] and DBP of 2.0mmHg [95% CI: 0.46; 3.52]), compared to those who worked at night for ≤9 years. Conclusion: these findings suggest that effects of night work begin after a certain exposure dose, i.e, after 9 years of night work or when exposed to night work for more than 4 nights per fortnight.