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

Objective: 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 (FEV(1) ; r = 0.07, P = 0.70). Conversely, the 6MWD correlated with FEV(1) 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 FEV(1) (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.