Medication adherence and associated factors in newly diagnosed hypertensive patients in Japan: the LIFE study

Hypertension is the leading cardiovascular risk factor worldwide. However, in Japan, only 30% of patients have their blood pressure controlled under 140/90 mmHg, and nonadherence to antihypertensives is thought to be a reason for the poor control of hypertension. We therefore sought to assess the adherence to hypertension treatment and to evaluate factors influencing patients' adherence in a large, representative sample of the Japanese population. To this end, we analyzed claims data from the LIFE Study database, which includes 112 506 Japanese adults with newly diagnosed hypertension. Medication adherence was measured for a year postdiagnosis using the proportion of days covered (PDC) method. Factors associated with adherence to antihypertensives were also assessed. Among the total 112 506 hypertensive patients, the nonadherence rate (PDC ≤ 80%) for antihypertensives during the first year after initiation of the treatment was 26.2%. Younger age [31-35 years: odds ratio (OR), 0.15; 95% confidence interval (95% CI), 0.12-0.19 compared with 71-74-year-old patients], male gender, monotherapy, and diuretics use [OR, 0.87; 95% CI, 0.82-0.91 compared with angiotensin II receptor blockers (ARBs)] were associated with poor adherence in the present study. Cancer comorbidity (OR, 0.84; 95% CI, 0.79-0.91 compared with no comorbidity), prescription at a hospital, and living in a medium-sized to regional city were also associated with poor adherence. Our present findings showing the current status of adherence to antihypertensive medications and its associated factors using claims data in Japan should help to improve adherence to antihypertensives and blood pressure control.