Association of Inadequate Health Literacy with Health Outcomes in Patients with Type 2 Diabetes and Depression: Secondary Analysis of a Controlled Trial

Objective: To examine the relationship of inadequate health literacy (HL) with changes in depressive symptoms, health-related quality of life and cardiometabolic outcomes in patients with type 2 diabetes mellitus recently screened positive for depression. Methods: Secondary analysis of data from a clinical trial (N = 154) that compared a collaborative team care model and enhanced usual care for primary care for patients with type 2 diabetes and depression. The exposure of interest was inadequate HL, defined as a total summative score of 9 or more on the 3 brief screening questions. Outcomes of interest were differences in the changes in depressive symptoms (Patient Health Questionnaire-9 (PHQ-9) at 12 months, health-related quality of life (short-form health survey 12 [SF-12]) and European Quality of Life-5 Dimensions questionnaire (EQ-5D), glycemic control (A1C), low-density lipoprotein cholesterol and systolic blood pressure. Results: The average age of patients was 58 years; 56% were women and were predominantly white. Only a small proportion (n = 24; 16%) had inadequate HL. In adjusted random effects models, there were no statistically significant or clinically important differences in all outcomes between the HL groups. The between-group differences in change over 1 year were -0.55 points for PHQ-9; 0.76 points for physical and 0.56 points for mental summaries of the SF-12; 0.03 points for EQ-5D; -0.17 for A1C; -0.08 mmol/L for low-density lipoprotein; and -1.94 mm Hg for systolic blood pressure. Conclusions: Among primary care patients with type 2 diabetes who had been screened recently as being positive for depression, it is unlikely that HL impacts health outcomes over 1 year. (C) 2015 Canadian Diabetes Association