Does the relationship between asthma and obesity differ by neighborhood?

Summary Background Prior studies suggest that obesity may cause asthma. Obesity and asthma are prevalent in low-income urban neighborhoods, but the impact of obesity on asthma in such neighborhoods has not been examined. Methods The New York City Department of Health and Mental Hygiene surveyed 6119 adults age 18–54 years in 2002. Obesity was defined as body mass index ≥ 30 kg/m2 and current asthma as physician diagnosed asthma plus recent symptoms. We calculated prevalence (risk) differences (RD) and population attributable risk percents (PAR%). Results Obese individuals had a 2.0% (95% CI: 0.5%, 3.6%; p = 0.01) higher risk of current asthma than normal weight individuals overall. Obesity was more common in low-income neighborhoods compared with middle-to-upper-income neighborhoods (23% vs. 14%, p < 0.001), as was current asthma (6% vs. 4%, respectively, p = 0.02). The risk of current asthma associated with obesity was similar in low-income (RD: 1.3%, 95% CI: −1.5%, 4.0%; p = 0.36) and middle-to-upper-income neighborhoods (RD: 2.0%, 95% CI: 0.1%, 3.9%; p = 0.04). The PAR% for asthma due to obesity was not greater in low-income (7.3%) than in middle-to-upper-income neighborhoods (7.7%). Conclusions It is unlikely that the excess asthma prevalence in urban low-income neighborhoods is disproportionately attributable to obesity. Instead, alternative causes of excess asthma should be sought.