Dose–response relationship between working hours and hypertension: A 22-year follow-up study

Hypertension causes a substantial burden to society. Some studies found that hypertension was associated with the working type and working hours. The purpose of the current study is to assess the dose–response relationship between working hours and hypertension. Data of 12,080 adults aged 18 to 65 years who attended the China Health and Nutrition Survey (CHNS) between 1989 and 2011 were analyzed. Hypertension was determined based on systolic and/or diastolic blood pressure measures, or having doctor-diagnosed hypertension. Multivariable Cox regression and restricted cubic spline to assess the dose–response relationship between working hours and hypertension. A total of 12,080 participants including 5852 females and 6228 males. By the last follow-up (2011), a total of 830 participants were hypertensive, with an incidence of 6.9%. After adjusting socio-demographic, lifestyle factors, as well as occupation type, compared with those who worked 35 to 49 hours per week, participants who worked no more than 34 hours per week (HR: 1.21, 95%CI: 1.03–1.41) and at least 56 hours per week (HR: 1.38, 95%CI: 1.19–1.59) had a higher risk of hypertension. The significant association between long working hours (at least 56 hours per week) and hypertension was observed among females (HR: 1.38, 95%CI: 1.16–1.64) and males (HR: 1.36, 95%CI: 1.04–1.78). Among manual workers, the relationship between long working hours and hypertension was observed (HR: 1.49, 95%CI: 1.10–2.02). The relationship between long working hours (HR: 1.21, 95%CI: 1.01–1.44) and short working hours (HR: 1.37, 95%CI: 1.16–1.61) and hypertension was observed among nonmanual workers. The hazard ratio of hypertension and working time displayed U-shape non-linear relationship (P(trend) < .001, non-linear P < .001). The non-linear response–dose relationship was found in manual worker, nonmanual worker, and male (P(trend) < .001, non-linear P < .001). The association between working time and hypertension showed U-shape relationship. Specifically, overtime work was an important occupational risk factors for adults, and short work time was related to hazard ratio of hypertension in nonmanual workers.