Asthma and insulin resistance in morbidly obese children and adolescents

Background. Obesity is well recognized as a state of increased insulin resistance and has been implicated as a significant risk factor for both asthma prevalence and asthma severity in children and adolescents. However, little is known about the specific factors that relate asthma and obesity. Recently, the pro-inflammatory state in obesity and its association with insulin resistance have been recognized. We hypothesize that the effect of morbid obesity on asthma is related to insulin resistance. Methods. The patient cohort in the obesity management program at the Children's Hospital of Wisconsin was retrospectively reviewed. Variables were collected from the program data base and chart review was done for missing variables. Patients were considered to have asthma if the evaluating physician confirmed the diagnosis through history and/or the patient had been on inhaled corticosteroids. Insulin resistance (IR) was calculated using a homeostasis model assessment (HOMA). Multivariate logistic regression was performed to identify variables that were significantly related to the odds of having asthma. Results. Of the 415 patients included in the study, 146 (35%) were asthmatic and 269 (65%) were non-asthmatic. The asthma (AG) and non-asthma (NAG) groups were similar with respect to mean age (11.3 vs. 11.5 years), gender (45% vs. 43% males), mean body mass index (BMI) (36.4 vs. 34.9), and exposure to smoking (43% vs. 42%). Fhx of asthma was significantly higher in AG (71%) compared to NAG (40%). IR level +/- SD was 8.5 +/- 9.7 in AG compared to 5.3 +/- 6.7 in NAG (p < 0.0001). Multivariate regression analysis found the following variables to be associated with having asthma: younger age (p < 0.05), smoking exposure (p < 0.05), positive Fhx of asthma (p < 0.0001, odds ratio of 3.1), and IR (p < 0.0001, odds ratio of 4.1). Conclusion. Morbidly obese asthma patients have a higher degree of insulin resistance compared to morbidly obese non-asthma patients. We speculate that the pro-inflammatory state of insulin resistance may contribute to the pathogenesis of asthma in obese patients. Future prospective studies should address insulin resistance as a possible risk factor for asthma in obese children and adolescents.