In this study conducted by the Kaiser Permanente Division of Research and the University of Washington School of Medicine, 72 percent of the 1,366 study participants had limited health literacy, and had significantly poorer adherence to newly prescribed antidepressants, compared to patients with no limitations.
"Research shows that those with health literacy limitations are more likely to have poor control of their chronic medical conditions such as diabetes, congestive heart failure and HIV," said Andrew Karter, PhD, research scientist at Kaiser Permanente and senior author on the study. "However, this is the first study to examine the association between health literacy and antidepressant adherence among patients with diabetes. This type of research gives our health care systems important feedback because, as providers, we often remain unsure whether the critical health information we convey to our patients is fully understood."
The Institute of Medicine defines health literacy as the capacity for patients to "obtain, process, and understand basic health information and services needed to make appropriate health decisions." Because nearly 90 percent of Americans have some difficulty using routine health information, the U.S. surgeon general has identified the improvement of health literacy as a national priority.
Adequate adherence for antidepressants is particularly important for patients with diabetes and other chronic medical conditions. Depression occurs twice as frequently among adults with diabetes compared to adults without diabetes, and has been associated with an increased risk of the serious diabetic complications, dementia and mortality.
In the study, health literacy was based on a self-reported scale in which participants with type 2 diabetes responded to three questions:
- How often do you have problems learning about your medical condition because of difficulty understanding written information?
- How confident are you filling out medical forms by yourself?
- How often do you have someone like a family member, friend, hospital or clinic worker or caregiver, help you read health plan materials?
Poor adherence to antidepressant medications has been described previously, but what was not known is that those with health-literacy limitations were significantly less likely to take their antidepressant medications. In fact, diabetes patients with limited health literacy were much less likely to refill their antidepressant medications in a timely fashion than patients with no limitations. These patterns were not explained by other factors known to be associated with medication nonadherence, including age, race/ethnicity, English proficiency and income, which were accounted for in the study.
Depression in adults with diabetes is frequently chronic, suggesting the need for long-term antidepressant therapy. "The high rates of early discontinuation that were observed among adults with diabetes who had any health literacy limitation suggest that few of these individuals received an adequate course of antidepressant therapy. Getting that sufficient treatment is critical in preventing relapse and recurrence of depression," said lead author Amy Bauer, MD, of the University of Washington School of Medicine. "Physicians should be aware of this. For antidepressant treatment to succeed, patients with limited health literacy may require more intensive counseling and clearer explanations about use of antidepressant medications and closer follow-up."
The researchers said the study findings underscore the importance of national efforts to address healthy literacy, simplify health communications regarding treatment options, improve public understanding of the importance of depression treatment, and monitor antidepressant adherence.
Additional authors on the study include Wayne Katon, MD, University of Washington; Dean Schillinger, MD, University of California, San Francisco Division of General Internal Medicine; Melissa Parker, MS, Alyce Adams, PhD, and Howard H. Moffet, MPH, Kaiser Permanente Northern California Division of Research; and Nancy Adler, PhD, University of California, San Francisco Center for Health and Community.
This research was supported by funding from the National Institutes of Health.