Differences in adherence to antihypertensive medication regimens according to psychiatric diagnosis: results of a Korean population-based study.

OBJECTIVE: To identify the relationship between various types of psychiatric disorders and adherence to antihypertensive medication.
METHODS: We obtained data from claims submitted to the National Health Insurance, which covers almost the entire Korean population. Of the total of 2,454,844 patients who received prescriptions for antihypertensive medication during 2004, the study used data from 158,982 patients diagnosed with psychiatric disorders and 2,295,862 patients without psychiatric disorders according to International Classification of Diseases 10th Revision. We measured cumulative medication adherence (CMA) and compared the rates of appropriate level of adherence, defined as CMA > or =80%, between individuals with and without psychiatric disorders. We used multiple logistic regression to identify differences in antihypertensive medication adherence according to the type of psychiatric disorder.
RESULTS: Adherence to antihypertensive medication regimens was lower among patients with dementia, alcohol use disorders, psychotic disorders, and mood disorders-accounting for 15.4% of the patients with psychiatric disorders. On the other hand, the majority of patients (82.8%) who had substance use disorders, anxiety disorders, neurotic and somatoform disorders, and behavioral syndromes showed greater adherence. Overall adherence was higher in those with psychiatric disorders than in those without psychiatric disorders after adjusting for sociodemographic and clinical factors (odds ratio = 1.03, 95% Confidence Interval = 1.02-1.04).
CONCLUSIONS: Adherence to medication is reduced in patients with various types of psychiatric disorders, usually those accompanied by functional impairment. Effective strategies for improving medication adherence should be tailored to individual levels of function and psychopathology.