The Role of Adiposity in the Association Between Physical Activity and Blood Pressure in Children

Purpose: To analyze whether body adiposity mediates and/or moderates the association between time in moderate-to-vigorous physical activities (MVPA) and blood pressure in children. Methods: This was a cross-sectional study of 577 children aged 5 to 7 years old. MVPA was measured by accelerometry. Body mass index (BMI), waist circumference (WC), and the sum of tricipital and subscapular skinfolds (skinfolds) assessed children's body adiposity. Systolic (SBP) and diastolic blood pressure (DBP) were used as the dependent variables. Results: In the primary analysis adjusting for BMI or skinfolds measures, additional time in MVPA was associated with higher SBP. On the other hand, further analyses showed that children in the largest BMI tertile (beta(SBP):0.18; 95%CI: 0.12-0.24; beta(DBP):0.11; 95%CI: 0.05-0.17), waist circumference (beta(SBP):0.16; CI: 0.09-0.22; beta(DBP):0.08; CI:0.02-0.14), or sum of skinfolds (beta(SBP):0.18; CI: 0.11-0.24; beta(DBP):0.09; CI: 0.03-0.16) presented a positive relationship between MVPA and blood pressure whereas no positive association was observed for children in the first and second adiposity tertiles. Adiposity also mediated the association between MVPA and blood pressure. A decrease of 0.03 mmHg in the systolic blood pressure was observed by decreasing the sum of skinfolds for each additional minute per day in MVPA. A decrease in diastolic blood pressure of 0.02 mmHg was observed for each additional minute per day in MVPA, which was related to a negative association between time in MVPA and waist circumference and sum of skinfolds. Conclusion: Not accounting for the potential moderation and mediation role of adiposity may lead to misinterpretations in the MVPA and blood pressure relationship.