PURPOSE This study evaluated a novel composite measure of health literacy and numeracy by assessing its predictive validity for diabetes self-care activities and glycemic control. METHODS Patients (N = 102) with type 2 diabetes were recruited from a family medicine clinic at an academic medical center. Combined health literacy was assessed by combining the results of the Health Literacy Scale and the Subjective Numeracy Scale. Self-management activities were assessed by the Summary of Diabetes Self-Care Activities scale. Hemoglobin A1c (A1c) values were extracted from patients' medical records to assess glycemic control. Path models were used to test the predicted pathways linking health literacy and numeracy, independently and together, to self-management activities and glycemic control. RESULTS The mean combined literacy score was 72.0 (range, 33-104); the mean health literacy score alone was 43.9 (range, 14-56); and the mean numeracy score alone was 28.1 (range, 8-48). The direct effects results showed that the combined health literacy score (B = 0.107, P < .05) and the health literacy score alone (B = 0.234, P < .05) were significantly associated with self-care activities. The health literacy score alone also had a significant direct effect on A1c (B = -0.081, P < .05). The indirect effects of the combined health literacy on glycemic control through self-care activities were not statistically significant. CONCLUSIONS Findings from this study suggest that the combined health literacy has predictive validity for self-care activities whereas the health literacy alone has predictive validity for glycemic control. More research is needed to validate these findings. Higher patient health literacy skills were not consistently associated with higher perceived numeracy skills. Additional attention and efforts should be made to make sure patients understand medical instructions involving numerical calculations.
