Self-reported adherence in patients with asthma

BACKGROUND: Not all patients with asthma adhere to their prescribed drug regimens. The Behavioral Model of Health Services Utilization, organized as predisposing, enabling, and need variables, may be useful in identifying variables related to adherent medication-taking behavior. OBJECTIVE: To examine the relationship between predisposing, enabling, and need variables and self-reported adherence with asthma controller drugs. METHODS: A secondary analysis was conducted from a cross-sectional study using survey and claims data obtained from adults with asthma enrolled in a managed care organization. Independent variables included predisposing (age, gender, race, years with asthma, number of comorbidities, health beliefs), enabling (income, number of metered-dose inhaler [MDI] instructors, inhaler technique, perceived physician access), and need (patient-perceived severity, symptom-derived severity, health-related quality of life). Adherence was measured using a 4 item questionnaire scored as the mean of the responses, with 5 denoting highest adherence. Multivariate regression analysis was used to identify variables with statistically significant relationships to self-reported adherence. Stepwise backward elimination was used, with the final model consisting of variables considered significant at p less than 0.05. RESULTS: The 573 respondents (1270 packets sent; 45% response rate) were primarily white (89.5%) and female (71.0%), with an average age of 40.5 +/- 12.4 years (mean +/- SD) and average asthma duration of 18.3 +/- 14.2 years. The mean adherence scale score was 3.7 +/- 1.1, with 84.6% indicating some level of nonadherence (score < 5). The final model had an adjusted R-2 of 0.26 and included 6 independent variables. Better adherence was associated with stronger beliefs in the benefits of treatment and trigger avoidance, greater perceived asthma severity, longer asthma duration, more MIDI instructors, and higher scores on the Short-Form 36 mental component summary. CONCLUSIONS: Complex beliefs, perceptions, and experiences constitute the variables associated with adherent medication-taking behavior. Future longitudinal studies should include these variables to determine the predictive strength of the model.