How Does Depression Influence Diabetes Medication Adherence in Older Patients?

Using various measures (electronic monitoring, patient/provider report, pharmacy data), the authors assessed the association between depression and diabetes medication adherence among older patients with Type 2 diabetes. Patients completed a baseline survey on depression (Patient Health Questionnaire) and were given electronic monitoring caps (EMCs) to use with their oral hypoglycemic medication. At the time of the patient baseline survey, providers completed a survey on their patients' overall medication adherence. Upon returning the caps after 30 days, patients completed a survey on their overall medication adherence. EMC adherence was defined as percent of days out of 30 with correct number of doses. Using pharmacy refill data from the patient baseline through 1 year later, they defined adherence as the percentage of days with adequate medication, based on days' supply across refill periods. Of 203 patients (mean age: 67 years), 10% (N = 19) were depressed. Depressed patients were less likely to self-report good adherence and had a lower median percentage of days with adequate medication coverage (on the basis of pharmacy refill data). After adjustment for alcohol use, cognitive impairment, age, and other medication use, depression was still negatively associated with adequate adherence, according to patient report and pharmacy data. Depression showed no associated with adherence on the basis of provider or EMC data. Depression was independently associated with inadequate medication adherence on the basis of patient self-report and pharmacy data.