Impact of obesity in asthma: Evidence from a large prospective disease management study

Background: Asthma and obesity continue to have a significant effect on public health. It is widely accepted that obesity may be an independent risk factor for asthma and affect asthma severity and quality of life (QOL). Objective: To examine the relationship between body mass index (BMI [calculated as weight in kilograms divided by height in meters squared]) and asthma severity, spirometry findings, health care utilization (HCU), and QOL. Methods: This 12-month prospective randomized controlled trial comparing disease management with traditional care enrolled 902 patients (473 pediatric and 429 adults) representing an underserved population. Data collected at baseline and at 6-month intervals included demographics, asthma severity, medication use, spirometry findings, and HCU. The QOL was assessed using the pediatric and adult versions of the Asthma Quality of Life Questionnaire and the 36-Item Short Form Health Survey. All HCU was determined by means of patient interview and extensive medical record review. Data were analyzed using negative binomial regression and analysis of variance. Results: In children, 45% were overweight/obese (17% with BMIs >85th percentile; 28% with BMIs ≥95th percentile). In adults, 58% were obese (BMIs ≥30). There was no relationship in children between BMI and severity of asthma, spirometry findings, QOL, or HCU. In adults, there was no relationship between BMI and asthma severity or HCU. Higher BMI was associated with a significant reduction in QOL (P < .001). The BMI had an inverse relationship with forced vital capacity but with no other spirometric values. Conclusions: Obesity was not associated with worse asthma severity, spirometry findings, QOL, or HCU in children. In adults with asthma, obesity was associated with lower forced vital capacity and QOL but not with severity or HCU.