Health literacy and health-related quality of life in adults with type 2 diabetes: a longitudinal study

Abstract

To examine the association of health literacy (HL) with changes in health-related quality of life (HRQL) among patients with type 2 diabetes. Data from a cohort study of type 2 diabetes patients were used. HL was assessed using 3 previously validated screening questions and HRQL using the EQ-5D-5L and SF-12 [physical and mental composite summary scores (PCS, MCS)]. The associations of baseline HL with changes in EQ-5D, PCS, and MCS scores over 1year and with directions of changes (no change; declined; improved) were examined. Missing data were handled with multiple imputation and sensitivity analyses. Average age of participants (N=1948) was 64.6±10.9years, 45% were female, and 12.6% had inadequate HL. Participants had mean decrements of 0.01 in EQ-5D, 1.0 in PCS, and 1.2 in MCS over 1year. In adjusted analysis, HL was not associated with changes in EQ-5D over 1year (β=0.01, P=0.146); however, patients with adequate HL had 2.1 points greater increase in PCS (P<0.001) and 3.1 points in MCS (P<0.001) compared to those with inadequate HL. Patients with adequate HL were less likely to have a decline in EQ-5D (RR 0.66; 95% CI 0.44, 0.98), PCS (RR 0.51; 95% CI 0.34, 0.76), and MCS (RR 0.49; 95% CI 0.33, 0.72) compared to those with inadequate HL. Patients with adequate HL were more likely to have an improvement in MCS compared to those with inadequate HL (RR 1.78; 95% CI 1.04, 3.04); such associations were not observed for PCS or EQ-5D. All results were robust in sensitivity analyses. Inadequate HL was independently associated with worsening HRQL in adults with type 2 diabetes, particularly in the mental health domain.