The Relationship of Ambulatory Blood Pressure to Physical Activity in a Tri-Ethnic Population of Obese and Nonobese Adolescents

BACKGROUND: The association between physical activity (PA) and ambulatory blood pressure (ABP) is documented in adults. This association and factors that may modify it, such as obesity, have not been reported in adolescents. The aims of this study were to determine the association of PA with ABP in 11- to 16-year-old adolescents, and to examine the modifying effects of obesity and other factors. METHODS: Data on 24-h ABP and PA were obtained from 374 adolescents using the wrist actigraph. Correlations between average PA for every 5-min interval preceding each BP measurement and ABP were calculated during the awake period. Mixed-effects models were used with ABP variables as separate, dependent variables. In addition to PA scores for 5 min preceding each BP, body mass index (BMI) z-score and other variables were added to the models as covariates and as interaction terms with activity. RESULTS: Correlations of PA for 5 min preceding BP measurements were 0.22 and 0.25 for systolic blood pressure (SBP) and diastolic blood pressure (DBP) respectively. In mixed-effects analysis, each 1-unit increase in PA was associated with an increase in SBP of 0.02 mm Hg, in DBP of 0.01 mm Hg, and in HR of 0.02 beat/min (P < .0001). The association of BP with PA was significantly less for those with higher BMI z-scores (SBP, P < .001, DBP, P = .027). The associations of PA with SBP and HR were modified by sexual maturation status of the adolescents. CONCLUSIONS: This study found that PA is associated with ABP measurements. These associations are modified by obesity status and other variables. Recognizing these associations may improve the interpretation of ABP measurements.