Objective: Children participating in a dietary clinical trial were studied to (1) assess physical activity patterns in boys and girls longitudinally from late childhood through puberty and (2) determine the association of level of physical activity on systolic blood pressure, low-density lipoprotein cholesterol, and BMI.
Patients and methods: In the Dietary Intervention Study in Childhood, a randomized clinical trial of a reduced saturated fat and cholesterol diet in 8- to 10-year-olds with elevated low-density lipoprotein, a questionnaire that determined time spent in 5 intensity levels of physical activity was completed at baseline and at 1 and 3 years. An estimated-metabolic-equivalent score was calculated for weekly activity; hours per week were calculated for intense activities. We hypothesized that weekly self-reported physical activity would be associated with lower systolic blood pressure, low-density lipoprotein, and BMI over 3 years. Longitudinal data analyses were performed for each outcome (systolic blood pressure, low-density lipoprotein, and BMI) by using generalized estimating equations with estimated-metabolic-equivalent score per week as the independent variable adjusted for visit, gender, and Tanner stage (BMI was included in models for systolic blood pressure and low-density lipoprotein).
Results: The initial study cohort comprised 663 youths (362 boys [mean age: 9.7 years] and 301 girls [mean age: 9.0 years], of whom 623 (94%) completed the 3-year visit. For every 100 estimated-metabolic-equivalent hours of physical activity, there was a decrease of 1.15 mmHg of systolic blood pressure. There was a 1.28 mg/dL decline in low-density lipoprotein for a similar energy expenditure. For BMI, an analysis of intense physical activity showed that for every 10 hours of intense activity, there was a trend toward significance with a 0.2 kg/m2 decrease.
Conclusions: Children with elevated cholesterol levels who lead a more physically active lifestyle have lower systolic blood pressure and a trend toward lower low-density lipoprotein over a 3-year interval. Long-term participation in intense physical activity may reduce BMI as well.