OBJECTIVE: Addressing the epidemic of poor compliance with antihypertensive medications will require identifying factors associated with poor adherence, including modifiable psychosocial and behavioral characteristics of patients.
DESIGN: Cross-sectional study, comparing measured utilization of antihypertensive prescriptions with patients' responses to a structured interview.
STUDY POPULATION: Four hundred ninety-six treated hypertensive patients drawn from a large HMO and a VA medical center.
DATA COLLECTION: We developed a survey instrument to assess patients' psychosocial and behavioral characteristics, including health beliefs, knowledge, and social support regarding blood pressure medications, , satisfaction with health care, depression symptom severity, alcohol consumption, tobacco use, and internal versus external locus of control. Other information collected included demographic and clinical characteristics and features of antihypertensive medication regimens. All prescriptions filled for antihypertensive medications were used to calculate actual adherence to prescribed regimens in a 365-day study period.
MAIN OUTCOME OF INTEREST: Adjusted odds ratios (ORs) of antihypertensive compliance, based on ordinal logistic regression models.
RESULTS: After adjusting for the potential confounding effects of demographic, clinical, and other psychosocial variables, we found that depression was significantly associated with noncompliance (adjusted OR per each point increase on a 14-point scale, 0.93; 95% confidence interval [95% CI], 0.87 to 0.99); in unadjusted analyses, the relationship did not reach statistical significance. There was also a trend toward improved compliance for patients perceiving that their health is controlled by external factors (adjusted OR per point increase, 1.14; 95% CI, 0.99 to 1.33). There was no association between compliance and knowledge of hypertension, health beliefs and behaviors, social supports, or satisfaction with care.
CONCLUSIONS: Depressive symptoms may be an underrecognized but modifiable risk factor for poor compliance with antihypertensive medications. Surprisingly, patient knowledge of hypertension, health beliefs, satisfaction with care, and other psychosocial variables did not appear to consistently affect adherence to prescribed regimens.