Lack of evidence of a link between health literacy and medication adherence

A doctor and patient discuss medicines

A lot of effort these days goes into educating people about good health.  Are people more likely to adhere to recommended treatments as a result?

Clinical question

In people with diabetes or cardiovascular disease, are people who have high health literacy more likely to adhere to treatment?

The review used a broad definition of health literacy, including concepts of education, numeracy and health literacy measurement tools in their search.

The evidence

Seven studies were found.  They were so different from one another that the reviewers decided to perform a narrative review instead of trying to pool the data in a meta-analysis.

They concluded that there was no evidence to show a correlation between health literacy and better treatment adherence.

Appraisal hints:

  • It seems likely that the literature search was inadequate to address the question.  It was restricted to English language articles and did not include sources beyond the mainstream biomedical literature reported in EMBASE and MEDLINE.
  • The studies were of poor quality.
  • The reviewers acknowledge the limitations imposed by the variable definitions of health literacy in these studies.
  • Although they call for more generalised research, it seems that this will simply compound the issues of heterogeneity and that more specific research focusing on specific interventions for particular populations is needed.
  • Given these factors, it seems likely that this review constitutes “absence of evidence” rather than “evidence of absence”.
  • You should look for more recent primary qualitative, observational and experimental research focusing on diabetes education and medication adherence among particular populations (e.g. Mayberry and Osborne 2012, Rausch, Hood et al 2012, Hernandez-Tejada, Campbell et al 2012).

Reference:

Authors: Loke YK, Hinz I, Wang X, Salter C.  Systematic Review of Consistency Between Adherence to Cardiovascular or Diabetes Medication and Health Literacy in Older Adults. Ann Pharmacother. 2012 Jun 5.