Functional health literacy and glycaemic control in older adults with type 2 diabetes: a cross-sectional study

OBJECTIVES To investigate the relationship between functional health literacy and glycaemic control in a sample of older patients with type 2 diabetes. DESIGN Cross-sectional study. SETTING A government-financed outpatient geriatric clinic in São Paulo, Brazil. PARTICIPANTS 129 older patients with type 2 diabetes, a mean (SD) age of 75.9 (6.2) years, a mean glycosylated haemoglobin (HbA1c) of 7.2% (1.4), of which 14.7% had no formal education and 82.9% had less than a high-school diploma. MEASURES HbA1c was used as a measure of glycaemic control. Functional health literacy was assessed with the 18-item Short Assessment of Health Literacy for Portuguese-speaking Adults (SAHLPA-18), a validated instrument to evaluate pronunciation and comprehension of commonly used medical terms. Regression models were controlled for demographic data, depressive symptoms, diabetes duration, treatment regimen, diabetes knowledge and assistance for taking medications. RESULTS Functional health literacy below adequate was encountered in 56.6% of the sample. After controlling for potential confounding factors, patients with inadequate functional health literacy were more likely than patients with adequate functional health literacy to present poor glycaemic control (OR=4.76; 95% CI 1.36 to 16.63). In a fully adjusted linear regression model, lower functional health literacy (β=-0.42; p<0.001), longer diabetes duration (β=0.24; p=0.012) and lack of assistance for taking medications (β=0.23; p=0.014) were associated with higher levels of HbA1c. Contrary to our expectations, illiterate patients did not have poorer outcomes when compared with patients with adequate functional health literacy, raising the hypothesis that illiterate individuals are more likely to have their difficulties recognised and compensated. However, the small subsample of illiterate patients provided limited power to reject differences with small magnitude. CONCLUSIONS Patients with inadequate functional health literacy presented with higher odds of poor glycaemic control. These findings reinforce the importance of addressing limited functional health literacy in clinical practice.