Antihypertensive medication adherence and mortality according to ethnicity: a cohort study.

Background: Few studies have evaluated adherence to antihypertensive medication in Chinese and South Asian populations and little is known about the long-term outcome. Our objectives were to compare adherence to antihypertensive medications and assess the association of adherence and long-term mortality in Chinese, South Asian, and white patients with newly diagnosed hypertension.

Methods: We conducted a retrospective cohort study of patients with hypertension who were new users of antihypertensive medications (1997-2005) using administrative data and a province-wide prescription database from British Columbia, Canada. Antihypertensive medication adherence within 1 year from the date of the first antihypertensive drug prescription was assessed using the 'proportion of days covered' metric. Proportion of days covered ≥ 80% indicated optimal adherence. Patients were followed for up to 10 years for mortality.

Results: There were 16,471 (11.1%) Chinese, 6099 (4.1%) South Asian, and 126,081 (84.8%) white patients who were prescribed antihypertensive medications. Compared with white patients, Chinese (odds ratio, 0.69; 95% confidence interval [CI], 0.67-0.72) and South Asian patients (odds ratio, 0.38; 95% CI, 0.36-0.40) were less likely to be optimally adherent to antihypertensive medications. Optimal adherence was associated with reduced mortality in white patients (risk-adjusted hazard ratio [aHR], 0.89; 95% CI, 0.85-0.93) but not associated with mortality in Chinese (aHR, 0.98; 95% CI, 0.83-1.17) and South Asian patients (aHR, 1.10; 95% CI, 0.84-1.44).

Conclusions: Chinese and South Asian patients with newly diagnosed hypertension were significantly less likely to adhere to antihypertensive medications than their white counterparts. However, optimal adherence in Chinese and South Asian patients was not associated with mortality.