The associations of shift work, sleep quality and incident of hypertension in Ontario adults: a population-based study

Background — Relatively few population-based studies have explored the relationship and potential mechanisms between exposure to shift work and hypertension. The study objectives for this study were to determine: (1) if history of shift work was associated with increased rates of hypertension among working adults; and, (2) if sleep quality mediated this relationship.

Methods — We conducted a population-based cohort study using data from Ontario respondents (aged 35-69) of the 2000-01 of Canadian Community Health Survey (CCHS), which was linked to administrative health data housed at Institute for Clinical Evaluative Sciences (ICES). Our sample included survey participants who were employed with no previous diagnosis of hypertension (n=7420). During a 12-year follow-up window, we determined the time of hypertension diagnosis based on a previously validated algorithm; and explored the mediating effect of sleep quality using marginal structural effect models.

Results — The study sample included 2079 shift workers and 5341 day workers. Shift workers reported less refreshing sleep, more trouble sleeping, and poorer sleep quality overall compared to day workers. In 12 years of follow-up, 31.3 % of workers developed hypertension. History of shift work was associated with higher hypertension rates in both men (HR=1.21, 95% CI: 1.02-1.44) and women (HR=1.26, 95% CI: 1.03-1.55). There was no evidence that these associations were mediated by past sleep quality.

Conclusions — History of shift work schedules is associated with increased rates of hypertension. Shift work disrupts sleep, but further longitudinal studies are needed to determine if sleep quality mediates the association between shift work and hypertension.