Factors associated with poor adherence to medication among hypertensive patients in twelve low and middle income Sub-Saharan countries

Abstract

Introduction: Over the past few decades, the prevalence of hypertension has dramatically increased in Sub-Saharan Africa. Poor adherence has been identified as a major cause of failure to control hypertension. Scarce data are available in Africa.

Aims: We assessed adherence to medication and identified socioeconomics, clinical and treatment factors associated with low adherence among hypertensive patients in 12 sub-Saharan African countries.

Method: We conducted a cross-sectional survey in urban clinics of both low and middle income countries. Data were collected by physicians on demographics, treatment and clinical data among hypertensive patients attending the clinics. Adherence was assessed by questionnaires completed by the patients. Factors associated with low adherence were investigated using logistic regression with a random effect on countries.

Results: There were 2198 individuals from 12 countries enrolled in the study. Overall, 678 (30.8%), 738 (33.6%), 782 (35.6%) participants had respectively low, medium and high adherence to antihypertensive medication. Multivariate analysis showed that the use of traditional medicine (OR: 2.28, 95%CI [1.79-2.90]) and individual wealth index (low vs. high wealth: OR: 1.86, 95%CI [1.35-2.56] and middle vs. high wealth: OR: 1.42, 95%CI [1.11-1.81]) were significantly and independently associated with poor adherence to medication. In stratified analysis, these differences in adherence to medication according to individual wealth index were observed in low-income countries (p<0.001) but not in middle-income countries (p = 0.17). In addition, 26.5% of the patients admitted having stopped their treatment due to financial reasons and this proportion was 4 fold higher in the lowest than highest wealth group (47.8% vs 11.4%) (p<0.001).

Conclusion: This study revealed the high frequency of poor adherence in African patients and the associated factors. These findings should be useful for tailoring future programs to tackle hypertension in low income countries that are better adapted to patients, with a potential associated enhancement of their effectiveness.

Fig 1. Adherence to medication according to countries.

Squares represent OR and lines, 95% confidence interval (CI). ORs derived from logistic regression analysis adjusted on age, patient wealth index, complications, use of traditional medicine and antihypertensive drugs with a random effect on country to account for intra and inter-country variability.

Fig 2. Odds ratios of patient’s factors significantly associated with low adherence level in multivariate analysis.

Squares represent OR and lines, 95% confidence interval (CI). ORs derived from logistic regression analysis adjusted on age, patient wealth index, complications, use of traditional medicine and antihypertensive drugs with a random effect on country to account for intra and inter-country variability.

Fig 3. Percentage of patients according to their adherence level by patient wealth index stratified by country-level income.

Fig 4. Patients’ main reason for not taking their treatment.