Relationship Between Shift Work Years and Hypertension in Male Steel Workers:Based on Restricted Cubic Spline Model

Objective  To estimate the association of shift work years and hypertension based on restricted cubic spline model.

Method  A total of 6 013 male workers from a steel enterprise were investigated by face to face interview from September 2014 to June 2015, including basic information and occupational factors. Measurement of blood pressure was conducted at the same time. Chi-square test and non-conditional logistic regression model were used to assess the relationship between shift work and hypertension. Restricted cubic spline model was used to estimate the relationship between shift work years and hypertension.

Result  After adjusting age, body mass index (BMI), educational level, marital status, average family monthly income, smoking, drinking, physical activity, salt intake, parental/maternal hypertension, and high temperature and noise exposure, the prevalence rate of hypertension in the workers with current or former shift work was 1.255 times of those with never work (95%CI:1.026-1.536, 1.071-1.470). The results of restricted cubic spline model analysis showed a relationship with non-linearity (χ²=13.05, P<0.05) between shift work years and hypertension (χ²=52.62, P<0.05). After stratified by the age of first shift work, less-than-21-years-old was associated with decreased hypertension prevalence after 23 years of shift work, and equal-or-greater-than-21-years-old was associated with decreased hypertension prevalence after 32 years of shift work.

Conclusion  A relationship is identified between shift work years and hypertension in male steel workers.