AIRWEIGHS: Investigating Obesity as a Susceptibility Factor for Air Pollution in Childhood Asthma

Overview

Background: Asthma and obesity are public health crises that have concurrently risen over the past decades, affecting millions of children in the United States and disproportionately affecting low-income minority children in urban areas. The same children at highest risk for asthma and obesity also have greater exposure to indoor and outdoor pollution. Emerging evidence suggests that obesity may confer increased susceptibility to health effects of air pollution. Methods: Aiming to provide causal-level evidence of these observational findings, we propose a home intervention study to 1) test whether targeted reductions of indoor Particulate Matter (PM) concentrations improve the respiratory health of overweight inner-city children with asthma more than that of lean inner-city children with asthma and 2) investigate mediators of susceptibility to indoor PM among overweight versus lean children with asthma. We will accomplish these aims using a 1:1 randomized controlled trial of 200 children with persistent asthma (half normal weight, half overweight) living in Baltimore City. Participants will be randomized to receive either two active air purifiers containing high-efficiency particulate air (HEPA) filters or two sham air purifiers with their filters removed. Implications: If the aforementioned observational findings are confirmed, implications will be directly relevant to the over 170 million children around the world now estimated to be overweight or obese.

The primary object of this study is to determine the efficacy of a targeted environmental intervention among overweight inner city children as compared to normal weight inner city children with asthma. Specific Aim #1: To determine if overweight inner-city children, compared to lean inner-city children, have greater improvement in asthma with an air purifier intervention aimed at reducing indoor PM. Hypothesis 1: An intervention using HEPA filter air purifiers in the homes of inner-city children with asthma will be associated with greater respiratory improvement in overweight children than in normal weight children. Specific Aim #2a: To investigate mediators of susceptibility among overweight versus normal weight children with asthma. Hypothesis #2. Candidate mediators, including increases in a) tidal volume and thereby increases in doses of inhaled particles, b) inflammatory and oxidative stress responses, c) corticosteroid resistance, and d) sleep disordered breathing mediate increased susceptibility to indoor PM among overweight versus normal weight children with asthma. Children with asthma will be enrolled in the study for about 16 weeks. They will have three clinic visits, an overnight sleep study, and two home environmental assessments for one week each. They will have a home and clinical assessment before randomization and another home and clinical assessment about 12 weeks after randomization. The primary outcome measure is maximum number of asthma symptom days.