The 2003 National Assessment of Adult Literacy estimated that 30 million Americans are at Below Basic literacy level and are able to do only simple and concrete literacy tasks. Another 63 million are at the Basic literacy level and are only able to read and understand short and commonplace texts 1. Health Literacy was measured as a new and separate component in the 2003 National Assessment of Adult Literacy where 36% percent scored at the Below Basic or Basic health literacy level. Among adults 65 and older, 59% were at the Below Basic or Basic levels of health literacy 2.

As defined by the National Institutes of Health, health literacy is the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions 3. Health literacy encompasses more than just the ability to read written materials. It also means understanding the information in order to actively participate in managing health. Even people with average or strong reading ability could be at risk for low health literacy because they may find medical terminology and medical concepts foreign. Williams et al. 4 reported that over one third of the patients evaluated in two public hospitals were unable to read and comprehend basic health-related teaching materials.

A systematic review of U.S. studies concluded that nearly half of the total subjects had limited health literacy 5. Another study examined Medicare enrollees (many with chronic conditions including heart failure), and found that more than one third of the respondents had limited literacy 6.

Evidence continues to emerge about the adverse influence of limited health literacy on health outcomes. Limited literacy is associated with decreased knowledge of one's medical condition 789101112, non-adherence to treatment plans 9, poor self care behaviors 781314, and increased hospitalizations 1516. Dewalt's systematic review concluded that people who read at low levels are 1.5 to 3 times more likely to have an adverse outcome compared to people who read at higher levels 17.

Limited health literacy is associated with education 69121819, age 467812, ethnicity 691112, income 69, and chronic diseases including diabetes, AIDS, hypertension and asthma 67891420. Aged, minority, poor, and medically complex individuals are uniquely vulnerable in our convoluted health care systems and may be even more so if they are functionally low literate.

Little is known about the specific prevalence of limited literacy among adults with HF. Using a convenience sample of adults with diabetes we sought to determine the prevalence of limited literacy in diabetic patients with HF compared to those with diabetes and no HF. We also sought to determine if clinically relevant variables shown to be related to limited literacy in other studies, (age, sex, race, marital status, insurance, education, and income) impact literacy.

Nine hundred and ninety eight subjects provided complete data for literacy and heart failure. The mean age was 65 years and just over half were women. Most were white, had at least a high school education and had health insurance. Seventeen percent had limited literacy (STOFHLA < 22) (Table 1). Out of the 172 who reported heart failure, 137 (80%) reported currently receiving treatment for their heart failure, and 100 (58%) reported that their heart failure limits their activities. Compared to subjects without HF, those with HF were more likely to be male, older, less educated, and poorer. Twenty-seven percent of the subjects with both diabetes and HF had limited literacy, compared to 15% of the subjects who had diabetes but no HF (P < 0.001) (Table 1). A box plot (Figure 1) illustrates the variation in literacy between those with and without HF.

In unadjusted analyses, there was a significant relationship between HF and literacy (OR 2.05; 95% CI 1.39, 3.02; P < 0.001). Nine hundred and nine patients provided complete data for the multivariate analyses. After adjusting for age, sex, race, income, marital status, and health insurance, HF was still significantly associated with limited literacy (OR 1.55, 95% CI 1.00, 2.41, P = .05). When education was added to the model, the relationship between HF and literacy was no longer significant (OR 1.31; 95% CI 0.82 – 2.08; P = 0.26). Excluding the 27 subjects who reported they had poor vision or other physical impairments had little effect on the analysis. In all the analyses, limited literacy was significantly associated with older age, male sex, and low income, but not with race, marital status or health insurance (Table 2).

Unadjusted, the prevalence of limited literacy among adults with diabetes and HF is nearly twice as high (27%) as those with diabetes who do not have HF (15%). The overall prevalence of limited literacy in this population is on the low end of the reported range in a systematic literature review that found that 25–50% of adults in outpatient medical settings had limited literacy 5. Gazmararian and colleagues reported limited literacy in 27% to 44% of new Medicare enrollees in four large US cities in 1999 6. In a later study, the same group reported limited literacy in 36% of Medicare enrollees with chronic disease (116 had HF) 25. The lower prevalence reported here may reflect that this population is younger and less likely to be foreign born.

The relationship between literacy and HF was somewhat weaker but still statistically significant after adjusting for likely confounders such as age, sex, race, income, marital status and insurance (but not education). However, it became weaker still and lost statistical significance when controlling for education as well. This suggests that education is either in the causal chain or is a confounder with a direct relationship to both low literacy and heart failure. We find it implausible that heart failure directly causes low educational status, or that low educational status causes heart failure (at least directly). However, the data are consistent with a possible mediating role for literacy in the relationship between education and heart failure 26. In any event, adjusting for education may obscure the fact that, causal or not, literacy is highly associated with heart failure. One in four subjects with HF in this study may require alternatives to written materials to assist them in understanding their disease and following through with self-care. Although limited literacy may or may not be directly caused by HF per se, the high prevalence in this cohort warrants consideration when working with this population.

These data support previous reports of limited literacy among the elderly 56. Older adults have a large burden of chronic diseases and thus considerable health related reading demands 6. Given that the incidence of HF increases with age 27, and with the expanding group of older adults in America, the association of limited literacy and age becomes problematic from a clinical and practical point of view.

Many HF patients lack sufficient knowledge to manage their disease, highlighting the need for improved patient education 2829. Patients with limited literacy are significantly less likely to correctly answer questions about HF than those with adequate literacy 25. In addition, a number of investigators have reported deficient heart failure self-care behaviors among patients despite HF education 3031. The wide gap between receiving information that is presented and acting on it may be the result of low literacy. Limited literacy is likely to influence the learning of essential HF self-care skills leading to poorer health outcomes.

There are limitations to this study. The subjects all had diabetes, were enrolled in primary care, were primarily white, and lived in Vermont and bordering states in a mostly rural environment limiting generalizability. Subjects self reported whether or not they had HF and their response was not verified by their providers. We excluded subjects with significant cognitive impairment based upon assessment by their primary care provider. In addition, our study may be influenced by participation bias: individuals with limited literacy may have been more likely to decline to participate in the survey. We don't have any information on the 570 patients who declined to be interviewed other than many of them are younger and we surmise that their time commitment with work and other responsibilities may have limited their participation. The cross sectional design of the study tells us about associations and not causality and reflects the status of literacy at only one point in time. Additional studies are needed to determine the prevalence of limited literacy in adults with HF without diabetes.

Twenty-seven percent of the adults in this study who have 2 chronic health conditions, diabetes and HF, have limited literacy compared to 15% of the adults with diabetes that do not have HF. After adjusting for age, race, sex, income, insurance, and marital status (but not education), there continues to be a significant association between HF and limited literacy. The relationship of literacy and HF appears to be confounded or mediated by education. Health care providers need to be aware that adults with both diabetes and HF are at increased risk for having limited literacy. Understanding the extent of limited literacy among adults with chronic diseases can lead to enhanced efforts to improve patients knowledge and skills and ultimately, may improve the outcomes of their disease management.

The author(s) declare that they have no competing interests.

ASL conceived of the study, participated in the coordination, interpretation of the data, and drafted the manuscript. NM, BN participated in its design, performed statistical analyses, and interpreted the data. All authors reviewed the manuscript for important intellectual content and gave final approval.