OBJECTIVES: Chronic respiratory diseases accounts for 6.3% of global Years Lived with Disability (YLDs); COPD contributing to 29.4 million YLDs and asthma, 13.8 million YLDs. Literature reports adherence to asthma medication between 30-70% and that to Chronic Obstructive Pulmonary Disorder (COPD) medication at <50%. Knowing the prevalence and reasons for non-adherence to asthma/COPD medications are beneficial in developing both patient and population level adherence improvement interventions. This calls for the need to develop a reliable self-reported adherence measure so that reasons for non-adherence can be understood. The objective of this study was to establish the reliability of the Medication Adherence Reasons Scale (MAR-Scale) in measuring non-adherence in asthma/COPD and to describe the reasons for non-adherence.

METHODS: Data from the 2018 National Health and Wellness Study, a self-administered, annual, internet-based cross-sectional survey of US adults was used. Respondents who self-reported taking daily prescription medication(s) to treat asthma/COPD were given the MAR-Scale, a 20-item comprehensive scale. The scale has 19 items/reasons for non-adherence and one global item, that measures non-adherence “in the past 7 days”, on an 8-point scale ranging from 0 days to 7 days. Scale reliability was estimated using Cronbach’s alpha and confirmatory factor analysis. Frequencies were used to identify the reasons for non-adherence.

RESULTS: The Cronbach’s alpha for the MAR-Scale in asthma (N = 2,810) was 0.880 and 0.932 in COPD (N = 1,632). The Goodness of Fit Index (0.982, 0994) and Standardized Root Mean Square Residual (0.048, 0.036) was acceptable for asthma and COPD respectively. The medication non-adherence rate in asthma was 38.4% and 28.4% in COPD. The most common reasons for non-adherence for both conditions were “simply missing” and “skipping medication to see if still needed”; and cost for COPD.

CONCLUSIONS: The MAR-Scale demonstrated acceptable reliability with both asthma and COPD medications and provided an overall estimate for non-adherence.