Objectively-measured sedentary time and its association with markers of cardiometabolic health and fitness among cardiac rehabilitation graduates

Background: Sedentary time is an independent risk factor for cardiometabolic disease and mortality. It is unknown how much time individuals with coronary artery disease spend being sedentary or how their sedentary time relates to markers of health. The objectives of this study were to: (a) quantify sedentary time in a post-cardiac rehabilitation (CR) population, and (b) assess association with cardiometabolic risk, independent of moderate-to-vigorous physical activity. Design: Cross-sectional. Methods: As part of a larger trial, 263 recent CR graduates (similar to 10 days post-CR, mean age 63.6 +/- 9.3 years, 75% male) wore an ActiGraph GT3X accelerometer during waking hours (>= 4 days, >= 10 hours/day) to quantify sedentary time (<= 150 counts per minute). Spearman correlations were computed to assess relationships between sedentary time (adjusted for wear time) with markers of cardiometabolic health and fitness. Significant markers were examined using multiple linear regressions. Results: Participants spent an average of 8 hours/day sedentary (similar to 14 bouts/day). Sedentary time was negatively correlated with high-density lipoprotein and (V) over dotO(2)peak and positively correlated with triglycerides, body mass index and waist circumference. After adjusting for age, sex, medications and moderate-to-vigorous physical activity, hours/day of sedentary time remained significantly associated with log(V) over dotO(2)peak (beta=-0.02, p=0.001) and body mass index (beta=0.49, p=0.02). Conclusions: Findings suggest that even among a group of post-CR individuals who are already probably more active than patients who have not undergone CR, sedentary time remains high and is associated with poorer cardiorespiratory fitness, suggesting a possible new area of focus among CR programs.