Background: Medication adherence can be affected by many factors, including health literacy. The purpose of this study is to determine (1) if a relationship exists between health literacy and self-reported or objectively measured medication adherence and (2) which aspect or aspects of medication nonadherence are most associated with health literacy.
Subjects and methods: This is a multicenter, cross-sectional survey study of adult patients with type 2 diabetes mellitus (T2DM), taking one or more antidiabetes medication for ≥6 months with a hemoglobin A1c (HbA1c) measure on record. Data collected included patient demographics (age, gender, race, language, highest level of education, injectable diabetes medication use, last HbA1c, and diabetes medication refill history) and two survey instruments (the Morisky eight-item Medication Adherence Scale [MMAS-8] and the short-form Test of Functional Health Literacy in Adults [s-TOFHLA]). Descriptive statistics and bivariate correlations were assessed, along with linear and logistic regression.
Results: One hundred ninety-two patients with an average HbA1c level of 8.1% were included. Of these subjects, 32.8% had limited health literacy as measured by the s-TOFHLA, 58.9% had low adherence as measured by MMAS-8, and 65.1% were nonadherent based on cumulative medication gap (CMG) analysis. Age was associated with s-TOFHLA (-0.411; P<0.01) and MMAS-8 (0.157; P<0.05) scores. HbA1c was associated with MMAS-8 (-0.209; P<0.01) and CMG (0.152; P<0.05) scores. There was no significant association between s-TOFHLA and MMAS-8 or CMG. However, s-TOFHLA was positively related to MMAS-8 question 8, assessing difficulty remembering to take medications (P=0.017).
Conclusions: Health literacy level is not associated with self-reported or objectively measured medication adherence in underserved patients with T2DM. Lower health literacy scores are associated with a patient experiencing difficulty remembering to take medications.