Asthma is the most common chronic condition of childhood, yet the relationship between obesity and asthma risk and the impact of obesity on clinical asthma outcomes are not well understood. For this population-based, longitudinal study, demographic and clinical data were extracted from administrative and electronic health records of 623,358 patients aged 6-19 years who were enrolled in the Kaiser Permanente Southern California health plan in 2007-2011. Crude asthma incidence ranged from 16.9 per 1,000 person-years among normal-weight youth to 22.3 per 1,000 person-years among extremely obese youth. The adjusted risks of asthma for overweight, moderately obese, and extremely obese youth relative to those of normal weight youth were 1.16 (95% confidence interval: 1.13, 1.20), 1.23 (95% confidence interval: 1.19, 1.28), and 1.37 (95% confidence interval: 1.32, 1.42), respectively (Ptrend < 0.0001). The relationship between obesity and asthma risk was strongest in Asian/Pacific Islanders and in the youngest girls (aged 6-10 years), compared with other groups. Among youth who developed asthma, those who were moderately or extremely obese had more frequent asthma exacerbations requiring emergency department services and/or treatment with oral corticosteroids. In conclusion, obese youth are not only more likely to develop asthma, but they may be more likely to have severe asthma, resulting in a greater need for health care utilization and aggressive asthma treatment.
Keywords: asthma; body mass index; cohort studies; obesity; overweight; severe asthma.