Investigating the association between health literacy and non-adherence

Background Low health literacy is expected to be associated with medication non-adherence and early research indicated that this might be the case. Further research suggested that the relationship may be more equivocal. Aim of the review The goal of this paper is initially to clarify whether there is a clear relationship between health literacy and non-adherence. Additionally, this review aims to identify factors that may influence that relationship and ultimately to better understand the mechanisms that may be at work in the relationship. Method English language original research or published reviews of health literacy and non-adherence to orally administered medications in adults were identified through a search of four bibliographic databases (PubMed, EMBASE, CINAHL, and EBSCO Health). Results The search protocol produced 78 potentially relevant articles, of which 16 articles addressed factors that contribute to non-adherence and 24 articles reported on the results of research into the relationship between non-adherence and health literacy. Factors that contribute to non-adherence can be categorised into patient related factors, including patient beliefs; medication related factors; logistical factors; and factors around the patient-provider relationship. Of the 23 original research articles that investigated the relationship between non-adherence and health literacy, only five reported finding clear evidence of a relationship, four reported mixed results and 15 articles reported not finding the expected relationship. Research on possible mechanisms relating health literacy to non-adherence suggest that disease and medication knowledge are not sufficient for addressing non-adherence while self-efficacy is an important factor. Other findings suggest a possible U-shaped relationship between non-adherence and health literacy where people with low health literacy are more often non-adherent, largely unintentionally; people with moderate health literacy are most adherent; and people with high health literacy are somewhat non-adherent, sometimes due to intentional non-adherence. Conclusion It is clear that relevant research generally fails to find a significant relationship between non-adherence and health literacy. A U-shaped relationship between these two conditions would explain why linear statistical tests fail to identify a relationship across all three levels of health literacy. It can also account for the conditions under which both positive and negative relationships may be found.