People with poor health literacy find it difficult to obtain and understand medical information, and they are more likely to have physical or mental problems that produce pain and limit daily activities, according to an article in the September 26 issue of the Archives of Internal Medicine.
The American Institute of Medicine reported that 48 percent of adults in the US have inadequate health literacy, defined as the ability to obtain, process, and understand basic information and services needed to make appropriate decisions regarding health.

Michael S. Wolf, PhD, MPH, of the Feinberg School of Medicine, Northwestern University, Chicago, and colleagues used data from a survey of 2,923 Medicare enrollees in several different states. In a one-hour in-person interview, individuals' physical and mental health status were assessed. Questions included medical history, alcohol and tobacco use, and height and weight. Standardized mental and physical health test scores were determined. The average age of participants was 71 years.

Approximately one third of those surveyed had marginal (11 percent) or inadequate (22.2 percent) health literacy. Individuals with lower health literacy were more likely to have never smoked and to abstain from alcohol than individuals with adequate health literacy.

Individuals with inadequate health literacy had significantly higher rates of certain chronic conditions, including hypertension, diabetes mellitus, heart failure, and arthritis. Individuals with inadequate health literacy were more likely to report activity limitations related to health, including activities of daily living and pain that "quite a bit" or "extremely" interfered with normal work activities. "The magnitude of these associations were large and clinically important," the authors wrote.

Previous studies have suggested that inadequate health literacy is linked to worse knowledge of proper health behaviors and lower adherence to medical instructions; that despite access to health care the quality of medical encounters may be compromised when health care providers do not communicate at a level that is understood; and that patient education materials may be too complex or written at too high a level to be helpful. "Over time, these factors could contribute to the worse health status seen among the older patients with low health literacy in this study," the authors suggest3e.

"Although the causal pathways between low health literacy and disease-specific health outcomes remain unclear, this study provides further evidence of the likelihood that inadequate health literacy detrimentally affects health," the authors concluded.

"To develop appropriate and responsive interventions, future studies should discern how adults with lower health literacy recognize health issues, and they should identify barriers to seeking out appropriate health care services. In addition, interventions are needed that can help physicians and other health care professionals recognize and address the special needs of patients with limited health literacy."

In an editorial accompanying the article, Darren A. DeWalt, MD, MPH, and Michael P. Pignone, MD, MPH, of the University of North Carolina School of Medicine, Chapel Hill, wrote, "The study by Wolf and colleagues substantially expands our understanding of the relationship between low literacy and adverse outcomes. Patients with low literacy were also more likely to report having diabetes mellitus and heart failure but were not more likely to have asthma, cancer, or coronary artery disease. The relationship between literacy and the prevalence of chronic diseases has not been previously reported in such detail, to our knowledge. The finding of a higher prevalence of certain chronic conditions among people with low literacy is important because it raises the question about the role of literacy in the development of chronic conditions, rather than the common notion that literacy is most important once one develops a health problem. . . we can theorize that low literacy could have a causal role in their development."

"After the important study reported herein, we have more knowledge of the relationship between literacy and the prevalence of chronic disease, which opens the door for important inquiries about the reasons for these associations," the authors concluded. "Furthermore, these analyses offer the most rigorous estimates that we are aware of to date of the relationship between literacy and important patient-reported outcomes. As the evidence continues to build, we are more and more convinced that reading is fundamental, and one's health may depend on it."