8 hours of sitting time per day pose long-term risk of stroke

Among individuals with low physical activity (PA), excess leisure sedentary time of at least 8 hours daily translates to a heightened long-term stroke risk, as suggested in a study.

The study used data from the Canadian Community Health Survey, which included 143,180 healthy individuals without prior stroke, heart disease, or cancer. Researchers linked to hospital records to determine subsequent hospitalization or emergency department visit for stroke.

More than half (67 percent) of the population were <60 years of age. Mean daily leisure sedentary time was 4.08 hours overall, with slightly longer sedentary time among older people (mean, 3.9 hours for age <60 years, 4.4 hours for age 60–79 years, and 4.3 hours for age ≥80 years) and among women (mean, 4.2 vs 4.0 hours among men).

Over a median follow-up time of 9.4 years, a total of 2,965 stroke events (88.2 percent ischaemic) occurred. The median time from survey response until stroke was 5.6 years. Cox regression models and competing risk regression analyses showed a three-way interaction between leisure sedentary time, PA, and age.

In particular, the risk of stroke associated with ≥8 hours of sedentary time was pronounced only among individuals aged <60 years who were in the lowest PA quartile (fully adjusted hazard ratio, 4.50, 95 percent confidence interval, 1.64–12.3). This association was robust to multiple sensitivity analyses, including adjustment for mood disorders and when accounting for the competing risk of death.

The present data support efforts to promote PA and cut sedentary time in younger individuals.