Factors Associated with Adherence to Anti-Hypertensive Medication Among Patients Attending a Primary Health Centre in Ndola, Zambia: A Cross-Sectional Study

Abstract

Background: Hypertension is a leading modifiable risk factor for cardiovascular disease and premature death worldwide. Despite effective pharmacological therapy, poor adherence to anti-hypertensive medication remains the primary barrier to achieving blood pressure control, with non-adherence rates reaching 45-65% in sub-Saharan African settings. In Zambia, uncontrolled hypertension contributes substantially to hospital morbidity and mortality, yet context-specific data on adherence barriers remain limited. This study assessed factors associated with adherence to anti-hypertensive medication among patients attending Railway Surgery Urban Health Centre in Ndola, Zambia. Methods: A cross-sectional study was conducted among 237 hypertensive patients attending Railway Surgery Urban Health Centre in Ndola. A structured, interviewer-administered questionnaire assessed socio-demographic characteristics, clinical factors, and medication adherence using the modified Hill-Bone Compliance Scale. Data were analysed using descriptive statistics, chi-square tests, and multivariable logistic regression (p<0.05). Results: The overall adherence rate was 41.4%, with 58.6% of participants classified as non-adherent. The mean adherence score was 19.8 (SD=4.6) out of a possible 32. The most common reasons for non-adherence were running out of pills (mean=2.6), being away from home (mean=2.5), and forgetting to take medication (mean=2.4). Age (p=0.006), education level (p=0.001), and monthly income (p=0.001) were significantly associated with adherence. Clinical factors significantly associated with poorer adherence included presence of comorbidities (p=0.027), experience of side effects (p<0.001), and medication regimen complexity (p=0.007). Multivariable analysis identified age [≥]51 years (AOR=2.89-3.24), secondary/tertiary education (AOR=2.84-3.56), monthly income [≥]K1,000 (AOR=2.21-5.89), absence of comorbidities (AOR=0.51), absence of side effects (AOR=0.36), and simpler regimens (AOR=0.34) as factors independently associated with adherence. Health system barriers included long distances, reliance on public transport, missed appointments due to transport problems (35.4%), medication stock-outs (38.4%), and inadequate counselling time (49.8% received <5 minutes). Conclusion: Adherence to anti-hypertensive medication at Railway Surgery Urban Health Centre is suboptimal, with multiple socio-demographic, clinical, and health system factors associated with non-adherence. Interventions should focus on regimen simplification, proactive side effect management, enhanced patient education, and addressing systemic barriers including medication supply and transport access.