Despite the efficacy of antihypertensive treatment in preventing cardiovascular complications, there are often problems with medication adherence in hypertensive patients.

The objective of this study was to examine the medication adherence and its association with blood pressure (BP) control, cardiovascular disease (CVD) hospitalization, and all-cause hospitalization.

We conducted a retrospective cohort observation of patients who were treated for hypertension from January 2005 to December 2006.

Medical and pharmacy claims were obtained from Taiwan's National Health Insurance (NHI) database, whereas electronic records, including demographic characteristics and clinical information, were retrieved from a disease management program.

To determine the degree of medication adherence, we calculated the proportion of days covered (PDC) by filled prescriptions.

The associations of medication adherence with BP control, CVD hospitalization, and all-cause hospitalization were examined using multiple logistic regression models.

The study subjects comprised a total of 29,685 hypertensive patients. Of which, 40.1% of the patients had hypertension history of >5 years and 39.7% of patients had some comorbidity.

In total, 85.5% of patients were categorized as adherent, with PDC ≥80; 60% of adherent patients had good BP control.

Poor medication adherence was associated with poor BP control (odds ratio (OR) = 1.20, 1.13–1.29), CVD hospitalization (OR = 1.43, 1.14–1.81), and all-cause hospitalization (OR = 1.47, 1.21–1.78).

Our observation study clearly indicates that lower medication adherence is associated with poor BP control and higher risk of CVD and all-cause hospitalization in hypertensive patients.

American Journal of Hypertension 2010; doi:10.1038/ajh.2009.210

Pin-Hsuan Wu^1,2, Chuh-Yuh Yang³, Zhi-Lian Yao², Wei-Zhan Lin², Li-Wei Wu² and Chih-Ching Chang¹

• ^{1Department of Environmental and Occupational Health, Medical College, National Cheng Kung University, Tainan, Taiwan}
• ^{2Bureau of National Health Insurance, Taipei, Taiwan}
• ^{3Faculty of Public Health, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan}

Correspondence: Chih-Ching Chang, chang3@mail.ncku.edu.tw)