Impact of health literacy on health outcomes in ambulatory care patients: a systematic review.

OBJECTIVE

To examine the relationship between low health literacy and disease state control and between low health literacy medication adherence in the primary care setting.

DATA SOURCES

The following databases were searched for relevant articles from date of inception to April 2008: The Cochrane Database of Systematic Reviews, Cumulative Index to Nursing & Allied Health Literature, EMBASE, Education Resources Information Center, PsycINFO, International Pharmaceutical Abstracts, and Iowa Drug Information Service. MEDLINE was searched from 1966 to April 2008. Key words included literacy, health literacy, health education, educational status, disease outcomes, health outcomes, adherence, medication adherence, and patient compliance. Additional articles were identified by reviewing reference sections of retrieved articles.

STUDY SELECTION AND DATA EXTRACTION

Studies using a validated measure of health literacy and performing statistical analysis to evaluate the relationship between health literacy and disease state control or medication adherence were evaluated.

DATA SYNTHESIS

Eleven evaluations, including 10 discrete studies, met eligibility criteria. Six studies evaluated the relationship between health literacy and disease state control, 3 evaluated health literacy and medication adherence, and 1 study evaluated health literacy and both outcomes. A quality rating of poor, fair, or good was assigned to each study based on the study question, population, outcome measures, statistical analysis, and results. Eight studies had good quality, 1 was fair, and 2 were poor. Two high-quality studies demonstrated statistically significant relationships with health literacy, 1 with disease state control and 1 with medication adherence. Limitations of the other studies included inadequate sample size, underrepresentation of patients with low health literacy, use of less objective outcome measures, and insufficient statistical analysis.

CONCLUSIONS

There may be a relationship between health literacy and disease state control and health literacy and medication adherence. Future research, with adequate representation of patients with low health literacy, is needed to further define this relationship and explore interventions to overcome the impact that low health literacy may have on patient outcomes.