Cognitive Functioning, Comorbid Depression, and Medication Adherence in Adults with Type 2 Diabetes

Abstract

Suboptimal medication adherence is common among individuals with type 2 diabetes, therefore it is important to examine factors affecting adherence. Impairments in cognitive functioning associated with diabetes are related to medication non-adherence (Luzny, Ivanova & Jurickova, 2014). Depression is also associated with problematic self-management (Gonzalez et al., 2008) and can directly impair cognitive functioning (Snyder, 2013). The current study aimed to examine the relationships between cognitive functioning, depression, diabetes medication adherence and self-reporting biases. Participants were adults with sub-optimally controlled type 2 diabetes (N = 88, age range = 37-70, female = 50.0%) recruited through Massachusetts General Hospital who completed structured clinical interviews, cognitive measures, validated adherence self-report measures, and electronic monitoring of medication adherence. Discrepancy scores between self-reported and electronically monitored adherence were calculated. Depression symptom severity and cognitive functioning were each expected to have independent relationships to non-adherence (self-reported and electronically-monitored) and discrepancy scores. Multiple linear regression was the primary method of analysis. Results did not provide support for the independent effects of cognitive variables on adherence or discrepancy scores. Depression symptom severity significantly predicted worse self-reported medication adherence β = -.29,p = .01) and greater discrepancy scores β = .28, p = .01), but not MEMS adherence. When examined together, depression symptom severity retained its significance in predicting self-reported medication adherence and discrepancy scores, though the effects of cognitive functioning remained non-significant. Depression symptom severity significantly interacted with attention to affect self-reported medication adherence (R2Δ = .09, p< .001), verbal learning to affect self-reported medication adherence (R2Δ = .13, p< .001), and verbal learning to affect discrepancy scores (R2Δ = .19, p< .001). Post-hoc analyses revealed that at mild levels of depression symptom severity, lower attention was associated with higher self-reported medication adherence. At moderate levels of depression symptom severity, lower verbal learning was associated with higher self-reported medication adherence and lower discrepancy scores. Findings indicate that depression symptom severity is a significant independent predictor of adherence self-reporting biases. Additionally, depression symptom severity interacted with cognitive functioning to affect self-reported medication adherence, but not electronically monitored adherence, resulting in discrepancies between the two measures.