Studies of interventions to improve the health of persons with low literacy have increased in number over the past 10 years but remain relatively uncommon. Most completed studies have examined the effect of interventions on health knowledge or behaviors; fewer studies have examined interventions designed to mitigate the effects of low literacy on intermediate markers, measures of disease incidence or prevalence, or use of health services. No research to date has examined how interventions affect the general health status of persons with low literacy or whether interventions can affect health care costs or health disparities based on race, ethnicity, culture, or age. Because too few studies examined each type of intervention (brochure, videotape, computerized tool, or oral presentation), we are also unable to comment about which types of interventions might be most effective.
Completed studies to date have found mixed results: some have shown positive effects on health, others have found no effect. The diverse range of outcomes examined limited our ability to draw conclusions about effectiveness. Differences in study quality, as measured by our rating scale, did not appear to explain differences in effectiveness. Although several studies showed improved overall outcomes, most had not been designed to measure whether the intervention helped the participants with low literacy less or more than (or equally to) patients with higher literacy. We identified only 5 studies that did measure whether an intervention had different effects in persons with low versus high literacy. These studies all used controlled designs, measured literacy in all participants, and stratified their results according to literacy level, but to date such studies have examined only knowledge outcomes. Their findings were also mixed with respect to differences in their ability to improve health knowledge based on the user's literacy level: some found that interventions worked similarly in low-and high-literacy patients, others found that low-literacy patients benefited more than high-literacy patients, and still others found the opposite.
Although our review is to our knowledge the first to systematically identify and evaluate interventions for low-literacy patients, it should be interpreted in the context of several limitations. First, as with all systematic reviews, its findings depend on the quality of the information in the published literature. Limitations of the available intervention studies include frequent use of nonrandomized designs and nonconcealment of allocation; infrequent reporting of how health outcomes were assessed, including whether assessors were blinded to literacy and intervention status and whether the questions were administered in ways that would allow accurate responses by participants with limited literacy; poor description of interventions; and use of multimodal interventions that make it difficult to know which portions produced positive effects. Moreover, published research has focused on knowledge rather than more meaningful health outcomes, and we encountered so many different outcomes that quantitative synthesis (meta-analysis) of results was not possible.
Our review process also had some limitations. We did not include studies that did not measure literacy directly. As such, we may have failed to identify interventions that could be beneficial for patients with low literacy. Our quality grading system, although based on previous research, has not been independently validated, relies solely on information reported in published articles, and should be interpreted cautiously. In addition, we did not, for time and resource constraint reasons, conduct dual, independent, blinded review of all articles for inclusion or for abstraction of information into evidence tables. We believe, however, our modified process allows sufficient rigor to minimize potential selection bias.
Because currently available intervention studies leave many important questions unanswered, additional research is key to advancing this field. In particular, we need more intervention studies that examine whether the association between low literacy and adverse health outcomes is mainly direct (meaning that outcomes could be improved by interventions designed to overcome limitations in reading and quantitative reasoning) or indirect (such that outcomes might be better addressed by focusing on other underlying causes of health disparities such as poverty, lack of access to care, or racism).
Future studies should carefully specify research questions and comparisons to allow stronger conclusions to be drawn about the interventions' true value and to help clarify whether interventions work directly by affecting the ability of patients to understand health information or indirectly by overcoming other barriers.
Intervention studies should stratify results by literacy level. Without such analysis, readers cannot determine whether the intervention is more or less effective in the low-literacy group and whether it helped to ameliorate the differences in outcome according to literacy status. We have highlighted in this report the studies that perform this type of analysis. All used health knowledge as the main outcome, but their conclusions about the interaction between the effectiveness of the intervention and patient literacy levels were mixed.
Intervention studies have generally focused mostly on short-term knowledge outcomes or health behaviors. Future studies should link short-term knowledge changes to important, longer-term health outcomes that matter more directly to patients and their families. Interventions aimed at changing health behaviors such as dietary intake for patients with low literacy also face the challenge that changing such behavior has been difficult for patients, regardless of literacy level. Further, many interventions had multiple components. Analyses that examine the individual effects of the key intervention components could significantly advance the field and help us determine “how much” intervention is enough to improve health.
Another limitation of the literature is that few studies presented details about the nature of the intervention materials beyond reading level or about how patient outcome assessments were performed. Research suggests that people with low literacy skills can learn appropriate self-care tasks if the tasks are organized and presented in a fashion that facilitates incorporation into everyday life, but doing so effectively requires more than just developing easy-to-read written materials. More studies that examine and describe the tasks required for effective self-care and measure the ability of patients to learn those tasks may lead to more effective interventions. For example, rather than asking diabetes knowledge questions, researchers could analyze patient logs of insulin use based on glucose levels.
Finally, we need to conduct more studies that examine the effect on health outcomes of teaching persons with low literacy skills to read better. To do so will require collaboration between health researchers and experts in adult education and literacy training.
This review has important implications for practitioners as well. Health care providers, including physicians, nurses, and other health care personnel, should be alert to the widespread problem of low literacy, and should consider how to convey important health care information in ways that do not require advanced reading skills. They should have access to tools that have been shown to be effective, including videotapes, computer programs, and group education curricula. Practitioners can use the “teach-back” method to check to see that patients understand health information, a technique that has been associated with better outcomes in an observational study of diabetes.39
Structural changes in the way care is delivered, such as the use of disease management programs, may also have important benefits for patients with low literacy.40–42