Duration of initial antihypertensive prescription and medication adherence: a cohort study among 203,259 newly diagnosed hypertensive patients.

BACKGROUND:Optimal adherence with antihypertensive medications is crucial to prevent hypertension-related complications. This study evaluated whether the duration of initial antihypertensive prescription is associated with better medication adherence in a large sample of Chinese hypertensive patients. METHODS AND RESULTS:From a validated clinical database which consists of all patients in the public healthcare sector in Hong Kong, all patients on their first-ever antihypertensive agent from 2001 to 2005 (N=203,259) were included and followed-up for 12 months (and up to 5 years in separate analyses). The average age was 58.7 years (SD 17.3), and the overall rate of optimal adherence (as measured by having the Proportion of Days Covered≥0.80) was 32.4%. The proportion of patients whose initial prescriptions lasted for ≤6 days; 7-14 days; 15-28 days and ≥29 days was 23.7%, 24.3%, 15.1% and 37.0%, respectively. The corresponding proportion of optimal adherence was 18.1%, 20.1%, 31.0% and 50.3%. The binary logistic regression analysis showed that after controlling for age, sex, socioeconomic status, service type, drug class, and district of residence, those whose initial prescription was 7-14 days (adjusted odds ratio [AOR]=1.17, 95% C.I. 1.12-1.22); 15-28 days (AOR=1.90, 95% C.I. 1.82-1.99) and ≥29 days (AOR=4.13, 95% C.I. 3.96-4.31) were significantly more likely to be adherent than those who were prescribed for ≤6 days (all p<0.001). These findings remained significant in separate analyses where the period of follow-up was extended to 5 years. CONCLUSIONS:Shorter duration of first antihypertensive prescriptions was associated with poorer medication adherence, and this practice should be avoided if possible.