Adherence to combination therapy among ethnic Chinese patients: a cohort study

Discontinuation of antihypertensive combination therapy imposes a substantial public health burden, but few studies have addressed the factors associated with their discontinuation in Chinese patients. This study evaluated the association between patient age, gender, and number of comorbidities with discontinuation of combination therapies. From clinical databases, we included all adult patients prescribed an antihypertensive fixed-dose combination therapy during January 2004 to June 2007 in any government primary care clinics in one large Territory of Hong Kong. We studied the factors associated with drug discontinuation within 180 days after the first prescription date by multivariable regression analysis, controlling for age, gender, socioeconomic status, service setting, district of residence, visit types (new vs. follow-up), and the number of comorbidities. From 29 253 eligible patients, 7.1% discontinued their antihypertensive prescriptions. Younger (<50 years; adjusted odds ratios [aOR]: 0.78, 95% confidence interval [CI]: 0.66-0.92 for patients aged 50-59 years, P=0.003; aOR: 0.71, 95% CI: 0.60-0.84 for patients aged 60-69 years, P<0.001) and male patients (aOR: 1.19, 95% CI: 1.08-1.31, P<0.001) were more likely to have drug discontinuation. Patients with one (aOR: 0.64, 95% CI: 0.57-0.73, P<0.001) and at least two (aOR: 0.68, 95% CI: 0.54-0.87, P=0.002) comorbidities were less likely to have their medications discontinued. Combination therapies in Chinese patients had a low discontinuation rate when compared with Caucasian patients. Discontinuation was more likely among younger, male patients and those without concomitant comorbidities, in which more meticulous monitoring of their adherence patterns was needed.