Medication adherence and 24-h blood pressure in apparently uncontrolled hypertensive Nigerian patients

Uncontrolled hypertension is a major risk for major cardiovascular events. While medication adherence determines blood pressure (BP) control, studies on treatment adherence among apparently uncontrolled hypertensives are sorely lacking in sub-Saharan Africa. We report the pattern and correlate of medication adherence among the uncontrolled hypertensive population.

We investigated 148 age- and sex-matched hypertensive adults on anti-hypertensive medication for a minimum of 1 year. Apparent uncontrolled BP was defined as clinic BP ≥140/90 mmHg, whereas 24-h ambulatory BP monitoring was used to determine the true uncontrolled hypertension and other BP phenotypes. Using the 8-item Morisky medication adherence scale participants were classified into high, moderate and low adherence while Modified Morisky Scale was used to assess knowledge and motivation.

The mean age and BP were 61 ± 13.3 years and 158/91 mmHg, respectively. High adherence was found in 4.1% of the participants while 68.9% and 27% had moderate and low adherence, respectively. A third had true uncontrolled hypertension. A high proportion of the study participants also had a high motivation (68.9%) and knowledge (89.2%). Medication adherence was associated with motivation (P = 0.0001), knowledge (P = 0.002) and obesity (P = 0.036). Knowledge was an independent determinant of medication adherence with no significant effect on BP control.

High medication adherence was low and a third had true uncontrolled hypertension. Knowledge was an independent predictor of medication adherence with no significant effect on blood control. High medication adherence rather than moderate adherence, and knowledge are indeed needed for adequate BP control.