Self-Employment, Working Hours, and Hypertension by Race/Ethnicity in the USA

There is a large literature on work-related characteristics and hypertension, but studies on self-employment, longer working hours, and hypertension are mixed. Assessments of self-employment should be extended to account for people with part-time self-employment (i.e., employees also earning income from self-employment). The aim of this study was to determine the association of different types of self-employment with hypertension among adults by race/ethnicity and to assess whether longer working hours moderated these associations. Using data from the 2007-2018 National Health and Nutrition Examination Survey, measured hypertension (blood pressure >= 140/90 mm Hg) was assessed and employment categories included employees, part-time self-employment (i.e., employee with self-employment income), or full-time self-employment. Modified Poisson regressions and multiplicative interaction terms were used. Having full-time self-employment was associated with lower relative risk (RR) of hypertension compared to employees among Black (RR = 0.77, 95% confidence interval (CI) = 0.61-0.96) and White men (RR = 0.77, 0.65-0.93) compared to employees. Full-time self-employment was associated with higher risk of hypertension (RR = 1.36, 95% CI = 1.01-1.82) compared to employees among Hispanic women, while part-time self-employment was associated with lower risk (RR = 0.69, 95% CI = 0.48-0.98). Among White women, part-time self-employment was associated with higher relative risk of hypertension (RR = 1.27, 95% CI = 1.05-1.53) compared to employees. There were significant interactions between employment categories and longer working hours among Hispanic women as well as Black women and men. The results suggest that self-employment categories and longer working hours impact hypertension by race/ethnicity and sex. Because the number of full-time and part-time self-employed adults has increased, the health of this particular subgroup of workers should be further addressed.