Psychometric evaluation of a Korean version of the 8-item Medication Adherence Scale in rural older adults with hypertension

Abstract

Objective: To examine the psychometric properties of a structured self-reported 8-item Korean-version Morisky Medication Adherence Scale (MMAS-K) among rural older adults with hypertension.

Design: Cross-sectional descriptive survey.

Setting: A rural community comprising three primary health care posts in Gangwon Province, South Korea.

Participants: Ninety-two older adults with hypertension who received treatment at primary health care posts.

Main outcome measures: Participants completed an 8-item MMAS-K questionnaire, and the community health practitioners manually measured blood pressure. Factor analysis and correlation coefficient for validity and the Kuder-Richardson alpha coefficient for reliability of the MMAS-K were used, while the association between medication adherence and blood pressure control was determined using Fisher's exact test.

Results: Internal consistency reliability was acceptable with a coefficient alpha of 0.71. The factor analysis of construct validity identified two dimensions of the 8-item MMAS-K, explaining 52.22% of the total variance. There was a high correlation between the 8-item MMAS-K and the original 4-item MMAS (r = 0.874), indicating that these scales measure theoretically related constructs for convergent validity. There was a significant association between the 8-item MMAS-K score and blood pressure control (P < 0.05), indicating that, for the known-groups validity, the controlled blood pressure group was more likely to have higher rate of medication adherence than the poor-control group.

Conclusions: The findings indicate a positive association between medication adherence and blood pressure control. The 8-item MMAS-K possesses adequate validity and reliability among rural older adults with hypertension.

Keywords: chronic disease; international health; management of hypertension; psychometrics; rural nursing.