Adherence to Antihypertensive Medications in Type 2 Diabetes: Prevalence and Determinants

Aim: To estimate the extent of non-adherence to antihypertensive drugs in type 2 diabetes.
Study Design: Observational.
Place and Duration of Study: The study was conducted at three Belgian specialised diabetes centres during two months.
Methodology: Included were adult type 2 diabetes patients, treated with insulin and either ACE-inhibitors or sartans. Adherence was assessed electronically with the Medication Event Monitoring System. A standardised blood pressure measurement was taken at the study start and end.
Results: Mean age of the 130 included patients was 65 and 51% was male. Mean HbA1c was 7.5mg% (59mmol/mol), mean BMI 32kg/m2 and mean daily oral pill burden 8. Half of the patients showed perfect adherence and another fourth missed the prescribed dose on only 1 of 56 days. Mean baseline blood pressure was 143/77mmHg and 25% had controlled blood pressure (<130/<80mmHg). Higher hypertension knowledge was associated with adherence and higher daily doses of insulin with non-adherence. Adherence correlated positively to diastolic, but not systolic blood pressure. Of patients never missing a dose 78% reached controlled diastolic blood pressure compared to 68% of patients missing doses on ≥3 days.
Conclusion: Adherence to antihypertensive medications was high in this cohort followed up at specialised diabetes centres. Still, about 15-20% had suboptimal adherence and should receive adherence enhancing support, especially since high adherence seems necessary to obtain blood pressure control.