Abstract 16549: Longitudinal Associations of Accelerometer-Based Sedentary Time and Physical Activity With Blood Pressure Progression From Childhood Through Young Adulthood: A 13-year Mediation and Isotemporal Substitution Study of 2513 Children

Introduction: Randomized controlled trials in the young population concluded that moderate-to-vigorous physical activity (MVPA) was ineffective in lowering blood pressure (BP). The associations of cumulative sedentary time (ST), light physical activity (LPA), and MVPA with BP from ages 11 - 24 years, the isotemporal substitution of ST with LPA or MVPA, and the mediation path through which movement behaviour exact their impact on BP was examined.

Hypothesis: Increased ST would be associated with increased BP while cumulative LPA and MVPA would be associated with decreased BP.

Methods: Altogether 2513 children (61% female) from the Avon Longitudinal Study of Parents and Children birth cohort, UK who had data on at least one time-point measure of accelerometer-based movement behaviour across the follow-up and complete BP measures at ages 11, 15, and 24 years clinic visits were studied. MVPA was categorized into ≥60mins/day or less according to WHO’s PA guidelines. Longitudinal associations and isotemporal substitutions were examined with generalized linear-mixed effect models whereas the mediation path was examined using structural equation models, adjusting for cardiometabolic and other lifestyle factors.

Results: After full adjustment, a 1-minute cumulative ST from ages 11-24 years was positively associated with increased systolic BP (0.009 mmHg [95% CI 0.007 - 0.011]; p<0.001), and diastolic BP. A 1-minute cumulative LPA was associated with decreased systolic BP (-0.007 mmHg [-0.009 - -0.004]; p<0.001), but not diastolic BP. Persistent MVPA of ≥60mins/day was not associated with reduced systolic BP but paradoxically associated with increased diastolic BP (0.007 mmHg [0.002 - 0.013]; p=0.008). The longitudinal replacement of 10 minutes of ST with equal time in LPA during childhood, adolescence, and young adulthood cumulatively decreased systolic BP by -3 mmHg and diastolic BP by -2 mmHg during the 13-year follow-up period. Replacing 10 minutes of ST with 10 minutes of MVPA had no statistically significant effect. The positive association of ST with BP was fully mediated by lean mass (93% mediation).

Conclusions: Future guidelines may emphasize the importance of early LPA intervention from childhood for the prevention and treatment of elevated BP.