Association between physical activity and blood pressure in prepubertal children

Elevated blood pressure (BP) during childhood and adolescence increases the risk of hypertension in later life. Although physical activity is known to positively moderate BP, data regarding this relationship are limited in prepubertal children. We aimed to assess the association between a range of physical activities (including indoor and outdoor activity) and BP in a large community-based sample of prepubertal schoolchildren. Eligible year-1 schoolchildren (n=1765; mean age 6.7 ± 0.4 years) from a random cluster sample of 34 schools in Sydney, Australia, were examined. Parents completed detailed questionnaires about their child's activity. Height and weight were measured, and body mass index (BMI) was calculated. BP was measured using a standard protocol, and elevated BP was defined using published guidelines. Physical activity was classified as low, medium or high (that is, as tertiles). After adjusting for age, sex, ethnicity, height, BMI, parental qualifications and family history of hypertension and/or cardiovascular disease, children in the highest tertile of outdoor and indoor activities had significantly lower diastolic BP (∼1.5 mm Hg; P(trend)=0.01) and systolic BP (∼1.3 mm Hg; P(trend)=0.03), respectively, compared with those in the lowest tertile (reference). Linearly, time spent in indoor activities (each hour per day) was associated with ∼2.4 mm Hg decrease in diastolic BP (P=0.001). Physical activity was independently associated with lower BP in this sample of prepubertal children. The findings emphasize the importance of ensuring regular physical activity programs in primary schools to potentially reduce the risk of elevated BP in childhood and in later life.