Non-Compliance with Antihypertensive Medications Linked to Depression

Summarized by Robert W. Griffith, MD
August 23, 2002 (Reviewed: August 20, 2004)

Introduction

Several studies have shown that 50% of hypertensive patients don't take their medications as prescribed. This is a serious matter, given the consequences of uncontrolled hypertension, and it would be advantageous to know the reasons for non-adherence. Researchers at Brigham and Women's Hospital and Harvard Medical School designed a study to identify the factors associated with poor compliance with antihypertensive medication. This is a summary of their findings.

Method

The study compared the measured utilization of prescribed antihypertensives with results of structured interviews concerning psychosocial and behavioral characteristics. The subjects were hypertensive patients at a large Health Maintenance Organization (HMO) and a Veterans Affairs Medical Center (VAMC). Computerized information banks were used to identify members of both organizations who were 40 or over, had been diagnosed with hypertension, had filled an antihypertensive prescription during 1996, and were enrolled for 6 months before and 1 year after their first prescription. From this group, 513 HMO and 480 VAMC patients were asked, by mail, to participate in a 45-minute telephone interview; 48% (HMO) and 52% (VAMC) accepted the invitation.

Medication compliance was measured by analyzing the quantity of drug(s) dispensed and the days' supply to yield a calendar for each patient showing on which days the patient had enough drug available for use as directed. This allowed the number and percent of days covered by antihypertensive therapy to be calculated for the full year after the initial prescription. For the purpose of analyses, two cut points were used, corresponding to 80% and 50% of days covered, respectively.

The psychosocial and behavioral variables assessed at interview were:

• depression symptom severity -- using items from the Brief Symptom Inventory depression subscale
• health beliefs -- e.g. how important is it to take medications?
• knowledge of hypertension and its treatment
• social support in taking medication
• internal versus external locus of control -- "how much influence do I have over the things that happen to me?"
• patient satisfaction -- clinic waiting times, doctor's explanations etc.
• alcohol consumption
• tobacco use
• socially desirable responding -- to what degree does respondent give "approved" or "desirable" responses

Multivariable regression analyses were used to determine the associations between non-compliance and the psychosocial and behavioral variables. The most relevant results were adjusted odds ratios (ORs) of antihypertensive compliance for the different psychosocial/behavioral variables.

Results

The majority of the study population (248 patients each from the HMO and the VAMC) had the following characteristics: over 65, male, white, high school education level or below, retired, married, and not living alone.

The crude ORs between psychosocial/behavioral characteristics and medication compliance did not show any statistically significant relationships. However, further analyses were done controlling for demographic variables (age, gender, race, education, employment status, treatment site), thiazide diuretics, and co-morbid conditions (coronary artery disease, cerebrovascular disease, and renal failure). These showed that an increase in depression symptom severity was significantly associated with lower odds of compliance; the adjusted OR of good compliance had an increase of 0.93 (95% CI, 0.87 to 0.99) per point increase in the 14-point depression score.

The only other analyzed variable showing a relationship to compliance was the measure of external locus of control; the adjusted OR of good compliance per point increase was 1.14 (95% CI, 0.99 to 1.33 -- not significant). Thus patients who believed that events were largely out of their own control were more likely to be compliant medication takers.

Interestingly, there was no association between compliance and knowledge of hypertension, health beliefs, social supports, satisfaction with health care, and smoking or alcohol use.

Comment

The authors of the study claim this is the first report of a relationship between depressive symptoms and poor compliance with antihypertensive medication. Other studies have shown this effect for compliance with aspirin regimens, and treatments for AIDS, renal transplantation, and asthma. The present study, however, employs a larger collective and an improved method of measuring compliance.

The finding here may help explain the increased cardiovascular morbidity and mortality in depressed patients. Certainly, depressed patients should have their compliance with any medications checked frequently. Depression is largely under- treated and under-detected. And adequate diagnosis and treatment may have additional benefits in all conditions that require long-term medication.

Source

• Noncompliance with antihypertensive medications. The impact of depressive symptoms and psychosocial factors. PS. Wang, RL. Bohn, E. Knight,  et al., J Gen Intern Med, 2002, vol. 17, pp. 504--511

Related Links
Depression in the Elderly Can Predict Coronary Heart Disease
Risk Factors for Cerebral Hemorrhage in Hypertensive Patients

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