Income is an independent risk factor for worse asthma outcomes.

Abstract

Socioeconomic status (SES) is associated with asthma morbidity in observational studies, but the factors underlying this association are uncertain. We investigated whether 3 SES correlates-low income, low education, and high perceived stress-were independent risk factors for treatment failure and asthma exacerbations in the context of a randomized controlled trial. The effect of low SES (household income of <$50,000/y and household educational level of less than a Bachelor's degree) and high perceived stress (defined as a score of >20 on a perceived stress scale) on asthma morbidity was analyzed in 381 participants by using Poisson regression models. The primary outcome was treatment failure (defined in the trial protocol as a significant clinical or airflow deterioration), and the secondary outcome was asthma exacerbations requiring systemic corticosteroids. Fifty-four percent of participants had a low income, 40% had a low educational level, and 17% had high perceived stress levels. Even after adjusting for race and other important confounders, participants with lower income had higher rates of both treatment failures (rate ratio, 1.6; 95% CI, 1.1-2.3; P = .03) and exacerbations (rate ratio, 1.9; 95% CI, 1.1-3.3; P = .02). Adherence with inhaled corticosteroids was similarly high for both income categories. Education and perceived stress were not significantly associated with either outcome. In the context of a randomized controlled trial, participants with lower income were more likely to experience adverse asthma outcomes independent of education, perceived stress, race, and medication adherence.