Validity and Reliability of the Japanese Version of the Morisky Medication Adherence Scale-8 in Patients With Ulcerative Colitis

The Morisky Medication Adherence Scale is a clinically relevant tool used to evaluate medication adherence. In the current study, the validity and reliability of a Japanese version of the Morisky Medication Adherence Scale and factors related to low adherence were investigated in patients with ulcerative colitis. The original English version was translated into Japanese and then 3 institutions in Japan administered that Japanese version to 428 patients taking medication. Factor validity, internal consistency, and correlations between the Morisky Medication Adherence Scale and adherence were calculated on the basis of patients' own reports of skipped medication, and known group validity between clinically different groups was assessed. Logistic regression was used to assess relationships between low adherence and other factors. The Morisky Medication Adherence Scale identified 184 of 428 patients (43.0%) who exhibited low adherence. Confirmed factor analysis indicated one-dimensionality of the scale. Cronbach's alpha was 0.74. The Morisky Medication Adherence Scale score was significantly correlated with self-reported missed medication. Patients who were on concomitant induction therapy exhibited significantly better Morisky Medication Adherence Scale scores than those who were not. Patients with low adherence reported difficulty taking medicine, having proctitis, and ulcerative colitis duration of less than 5 years, and were of younger age. The Japanese Morisky Medication Adherence Scale yielded clinically relevant measures of adherence in patients with ulcerative colitis and may promote further international comparative studies.