Background: The impact of health literacy on longitudinal asthma outcomes is not known.
Objectives: To measure the association between health literacy and asthma outcomes and to assess how health literacy affects outcomes through covariates.
Design: Longitudinal cohort.
Patients: One hundred and seventy-five adult asthma patients.
Measurements: Independent variables measured at enrollment included demographic and asthma characteristics, depressive symptoms, self-efficacy, and asthma knowledge. Health literacy was measured with the Test of Functional Health Literacy in Adults. Outcomes were Asthma Quality of Life Questionnaire and SF-36 scores and emergency department utilization for asthma measured every 3 to 6 months for 2 years. The effects of health literacy on outcomes and interactions between health literacy and covariates were measured with multivariable models.
Results: The mean age of study participants was 42 years, and 83% were women. Less health literacy was associated with worse quality of life, worse physical function, and more emergency department utilization for asthma over 2 years (P< or = .05 for all comparisons). In multivariable analysis, health literacy did not remain statistically significant with any of the outcomes. Although the magnitude of its effect on emergency department utilization remained relatively intact, its effects on quality of life and functional status became attenuated with the sequential addition of covariates, particularly asthma knowledge.
Conclusions: Less health literacy was associated with poor longitudinal asthma outcomes. This relationship was both direct and indirect through effects on other independent variables, particularly patients' knowledge of asthma and self-management. Efforts to improve asthma outcomes should focus on improving literacy skills that are required to learn, understand, and implement effective self-management.