Effect of self-efficacy and social support on adherence to antihypertensive drugs

Abstract

Study objective: To determine the relationship between poor adherence and self-efficacy or social support after a pharmacist intervention.

Design: Post-hoc analysis of data from two randomized controlled trials of physician-pharmacist collaborative interventions (6 and 9 mo, respectively) to improve blood pressure control.

Setting: Eleven university-affiliated primary care clinics.

Patients: Five hundred eighty-four patients (aged 21-85 yrs) with uncontrolled primary hypertension; 296 were in the intervention group and 288 were in the control group.

Intervention: Pharmacists provided intensified hypertension management and drug adherence counseling to patients in the intervention group.

Measurements and main results: Social support and self-efficacy questionnaires were administered at baseline and end-of-study visits. Patient adherence was monitored by using the Morisky self-reported adherence questionnaire. Self-reported adherence scores improved significantly in the control group (p=0.0053) but not in the intervention group; however, adherence at baseline in both groups was high. There were small, but significant, improvements in self-efficacy (p<0.04) and social support (p<0.05) scores in the intervention group but not the control group at the end of the study. Social support and, to a lesser extent, self-efficacy improved as a function of duration of study participation (9-mo vs 6-mo intervention), regardless of whether the patient received the intervention. Blood pressure control in both groups improved significantly at the end of the study; however, mean blood pressure was significantly lower in the intervention group (129.7/76.6 mm Hg) compared with the control group (140.8/78.9 mm Hg; p<0.0001 for systolic, p=0.032 for diastolic).

Conclusion: Social support and self-efficacy improved significantly in the intervention group at the end of the pharmacist intervention. Drug adherence was correlated with self-efficacy even though drug adherence did not improve significantly in the intervention group. The fact that social support and self-efficacy improved as a function of duration of study participation suggests that participation in a research study may have had a positive influence on these measures. Even though the changes in social support, self-efficacy, and drug adherence were modest, there was significantly better blood pressure control in the intervention group compared with the control group. These findings indicate that changes in drug adherence, self-efficacy, or social support probably played a minor role in the blood pressure outcomes in these studies.