Medical Adherence in Diabetes-Hypertension Comorbidity: A Reply to Kilonzo et al (2017)
The article by Kilonzo et al (2017) evaluated control of hypertension in hypertension-diabetes comorbid patients in Ethiopia (1). High blood pressure in diabetic patients is associated with further risk of serious microvascular and macrovascular complications. The study is particularly relevant to the developing world in which 80% of the global diabetic population resides. I would like to make the following observations with respect to this study. The study collected data through evaluation of patient medical records. However, adherence to medications in the study was defined as patient self-reported use of the prescribed drugs which apparently requires validation by patient interview. The proportion of days covered method could instead be used to assess patient acquisition of medication through refill adherence during a specified period (2). This also requires that the medications refills should have been supplied to the patients through the health facility while also considering the potential for acquiring refills through out of pocket purchases. Furthermore, adherence is a dynamic behaviour which is subject to variation over time due to interaction of diverse patient and health factors (like acute sickness in patient with resulting inability to travel to clinic for drug refills). Hence, the time duration over which adherence was assessed should be stated especially since the longer the time duration, the higher the risk of recall bias. Regimen complexity and higher pill burden can lower medication adherence in diabetics (3). However, from the theoretical perspective of the health belief model, patients who suffer from diabetes-hypertension comorbidity may perceive greater susceptibility and severity of the associated complications on account of medication non-adherence. The authors could therefore have explored whether there was any difference in rate of adherence to anti-diabetic medications among the patients who were hypertensive compared to those who were normotensive. Moreover, was non-adherence to anti-hypertensive medications also associated with nonadherence to anti-diabetic medications? Finally, since self-care practices like daily exercise, consumption of fresh fruit and vegetables along with cessation of smoking are recommended in both the conditions, was there any significant difference in these behaviours among the hypertensive and the normotensive diabetic patients? In conclusion, the identification of the dominant predictors of adherence in comorbid DM-HTN patients and this can aid the development of effective interventions utilizing behaviour change communication for improving medical adherence.