Factors associated with antihypertensive drug compliance in 83 884 Chinese patients: a cohort study

Background Few studies address the profiles of antihypertensive compliance among ethnic Chinese. The levels of and factors associated with antihypertensive drug compliance among Chinese patients were evaluated in this study. Methods All Chinese hypertensive patients who paid at least two consecutive visits in any government primary care clinics for antihypertensive drug refill in a large territory of Hong Kong from January 2004 to June 2007 were included. Medication possession ratio (MPR), defined as the ratio of total days of medication supplied (not including the last prescription) to total days in a period of time, was used a measure of drug compliance. Results From 83 884 eligible patients, 71 685 (85.5%) had good compliance to antihypertensive drugs (MPR >= 80%). Binary logistic regression analysis was conducted, with good compliance as the outcome variable while controlling for potential confounders. Advanced age (adjusted ORs (aOR) 1.36-1.55, p < 0.001), female gender (aOR for male patients 0.84, 95% CI 0.80 to 0.87, p < 0.001), payment of fees (aOR 1.14, 95% CI 1.09 to 1.19, p < 0.001), attendance in family medicine specialist clinic (aOR 1.52, 95% CI 1.40 to 1.66, p < 0.001), follow-up visits (aOR 3.21, 95% CI 3.06 to 3.36, p < 0.001) and use of drugs acting on the renin-angiotensin system (aOR 1.18, 95% CI 1.07 to 1.30, p = 0.001) were positively associated with good compliance to drugs. Use of beta-blockers was negatively associated with drug compliance (aOR 0.78, 95% CI 0.73 to 0.84, p < 0.001). Conclusions Physicians should practice caution when prescribing antihypertensive drugs to patients with these factors where closer monitoring of their compliance patterns is warranted.