HealthDay News -- Just because patients don't ask questions doesn't mean they understand their diagnosis, take their medicines correctly or have insight into what they need to do to manage their care.

Nearly half of all American adults have low health literacy, according to the Institute of Medicine (IOM). In other words, they have difficulty understanding and acting upon health information. Anyone can have low health literacy, but it particularly affects older Americans and people who have lower incomes, limited education or limited proficiency in English.

While more study is needed to assess whether low health literacy causes poor health outcomes, the scientific evidence suggests at least an association. People with low literacy levels are less able to understand health information and less likely to seek preventive care, such as routine health screenings, the IOM noted in a 2004 report. They also use expensive services, like the emergency room, more frequently.

"I think what we're discovering is that health information and health systems are increasingly complex, and there is a gap between patients' knowledge and their ability to be able to use the health information and system in its complexity," explained Terry C. Davis, a professor of medicine and pediatrics at Louisiana State University Health Sciences Center in Shreveport whose research focuses on health literacy.

In interviews with 395 English-speaking adults at clinics in Shreveport, Jackson, Mich., and Chicago, Davis and colleagues tested patients' understanding of prescription instructions on each of five medication labels. People with lower literacy levels and those who took more prescription medications were less likely to understand.

"What we found out is that the labels on medications, though short and seemingly simple, were not clear to people," she said. For example, when the label read "take two pills twice daily," only about a third of the patients properly dosed out four pills.

Now Davis and colleagues are beginning to assess patients' understanding of the instructions on their own medications.

Meanwhile, the U.S. Food and Drug Administration is increasingly examining prescription labels and instructions to ensure that the information is clear to patients.

But prescription comprehension is only part of the problem. Interpreting a physician's instructions, often peppered in jargon, is another. As the IOM pointed out, a number of studies find that patients remember and understand as little as half of what their physicians tell them.

"The big barrier for the physician is trying to un-train himself from the medical terminology that he's used and come up with a lay-based language so that people can understand," said Sharon E. Barrett, a staff consultant to the Association of Clinicians for the Underserved in Tysons Corner, Va., and principal investigator on two health literacy studies.

Communicating clearly is important, she explained, because patients who understand their condition tend to be more compliant and get more involved in the management of their own care.

Legislation introduced by Sens. Tom Harkin (D-Iowa) and Norm Coleman (R-Minn.) in December 2007 would address the problem by creating a health literacy implementation center. Among other things, the center would seek to enhance Americans' ability to function as literate health consumers by disseminating health literacy resources and developing demonstration projects to test health literacy tools and interventions.

Physicians can do more, too. Davis teaches medical students to write down three things after a patient encounter to give to the patient: what the problem is, what he or she needs to do about it and why that's in the patient's best interest.

"If the doctor would slow down and do that, that would be very helpful for all patients," she said.

For almost ten years the American College of Physicians (ACP) Foundation has been working to improve health communication by addressing the problem of low health literacy.

More information about the Foundation's initiatives, as well as resources to improve patient understanding of health information, can be found on the ACP Foundation Web site.