Associations of obesity and asthma with functional exercise capacity in urban minority adolescents

Purpose To examine the independent association of asthma and obesity and of their co-existence with functional exercise capacity among urban adolescents. Methods One hundred eighteen Hispanic- and African-American adolescents including 33 obese asthmatics, 18 normal-weight asthmatics, 38 obese non-asthmatics, and 29 normal-weight non-asthmatics underwent anthropometric measures, 6-minute walk test (6MWT) as measure of functional exercise capacity and spirometry as measure of pulmonary function. The 6-minute walk distance (6MWD) was compared between the four study groups. The association of 6MWD with measures of lower airway obstruction, and measures of adiposity was assessed. Results The 6MWD was lower among the obese groups with the least distance covered by the obese asthmatic group (P = 0.02). In the obese asthmatic group, there was a negative correlation between 6MWD and body mass index (BMI) (r = -0.35, P = 0.03), but no association was noted with percent-predicted forced expiratory volume in the 1st second (FEV₁; r = 0.07, P = 0.70). Conversely, the 6MWD correlated with FEV₁ among normal-weight asthmatics (r = 0.45, P = 0.04) and normal-weight non-asthmatics (r = 0.4, P = 0.03), but was not associated with BMI in either of the two groups. After adjusting for age, height, gender, and ethnicity, BMI was noted to be a significant predictor (β -2.76, 95% CI -4.77 to -0.76, P < 0.01) of the 6MWD among the obese while percent predicted FEV₁ (β 1.87, 95% CI 0.28-3.45, P = 0.02) was a significant predictor among the normal-weight participants. Conclusions Our findings suggest that among urban minority obese asthmatic adolescents, functional exercise capacity was associated with obesity, rather than pulmonary function. Pediatr Pulmonol. 2012. 47:1061-1069.