Background Isotemporal substitution examines the effect on health outcomes of replacing sedentary time with light-intensity physical activity or moderate-to-vigorous intensity physical activity; however, existing studies are limited by cross-sectional study designs. Methods and Results Participants were 1922 adults from the CARDIA (Coronary Artery Risk Development in Young Adults) study. Linear regression examined the associations of sedentary, light-intensity physical activity, and moderate-to-vigorous intensity physical activity at year 20 (2005-2006) with waist circumference, blood pressure, glucose, insulin, triglycerides, high-density lipoprotein cholesterol, and a composite risk score at year 30 (2015-2016). Models then examined change in activity with change in cardiometabolic risk over the same 10-year period. Replacing 30 min/day of sedentary time with 30 min/day of light-intensity physical activity at year 20 was associated with a lower composite risk score (-0.01 SD [95% CI, -0.02, -0.00]) at year 30, characterized by lower waist circumference (0.15 cm [95% CI, -0.27, 0.02]), insulin (0.20 μU/mL [95% CI, -0.35, -0.04]), and higher high-density lipoprotein cholesterol (0.20 mg/dL [95% CI, 0.00, 0.40]; all P<0.05). An increase of 30 min/day in MVPA from year 20 to year 30, when replacing an equivalent increase in sedentary time, was associated with a decrease in the composite risk score (-0.08 [95% CI, -0.13, -0.04]) over the same 10 years, characterized by a decrease in waist circumference (1.52 cm [95% CI, -2.21, -0.84]), insulin (-1.13 μU/mL [95% CI, -1.95, -0.31]), triglycerides (-6.92 mg/dL [95% CI, -11.69, -2.15]), and an increase in high-density lipoprotein cholesterol (1.59 mg/dL [95% CI, 0.45, 2.73]; all P<0.05). Conclusions Replacement of sedentary time with light-intensity physical activity or moderate-to-vigorous intensity physical activity is associated with improved cardiometabolic health 10 years later.
Keywords: cardiometabolic risk; epidemiology; isotemporal substitution; physical activity; sedentary time.