Easton et al. BMC Public Health 2010, 10:459 http://www.biomedcentral.com/1471-2458/10/459 (perhaps via reduced ability to use written instructions and advice) to reduced adherence to effective medica- tion regimes and to serious medication errors [8]. Low functional literacy may affect health via its negative implications for social functioning and social status (including social stigma) [9]. Low health literacy is likely to be associated with limited knowledge of health and healthcare issues, which may contribute to poor self- management of long-term conditions [10-12]. It is difficult to differentiate between the implications of low functional literacy and low health literacy. There is clearly an overlap between the two concepts, but the relationship between them is not simple. While low functional literacy is very likely to impede the achieve- ment of high health literacy, a person may have high functional literacy but low health literacy. The measures of health literacy that are currently available do not assess all aspects of the concept [13] and much of what they do assess could be considered relevant to func- tional literacy as well. For example, the REALM focuses primarily on reading ability and does not examine moti- vation, understanding, or ability to access or use health- related information in any detail. In practice, then, assessments of health literacy are closely linked to assessments of functional literacy. People who are func- tionally literate are likely to score high on the existing measures of health literacy even though they may have low health literacy according to the definition given. The implications of low functional or health literacy for health are likely to be mediated or moderated by a number of factors, including the extent to which health services and health professionals recognize and make allowances for these. Low functional or health literacy is likely to be more readily recognized in some groups than others. For example, it will be evident in healthcare consultations that people from minority ethnic groups who do not speak the dominant language of their coun- try of residence or health service will have functional and health literacy difficulties in that context unless alternative language provision is made. When literacy difficulties are associated with language differences, they may be addressed through interpretation and transla- tion. Health professionals may also be more likely to consider the possibility of literacy difficulties among older than younger adults if they associate ageing with visual and/or cognitive impairments, or think that older cohorts were more likely to have missed out on school- ing as children. They might thus be more likely to give clear or increased oral instruction to older people. In developed countries with a compulsory education system, there may be a large ‘hidden population’ of peo- ple with literacy difficulties. The ability to communicate orally can mask the inability of many people who speak the dominant language well to read and write Page 2 of 10 competently. Some of these people are unaware they have low health literacy skills [1] and many are reluctant to disclose them and careful to use coping strategies that hide them [9]. Several studies have shown that health care staff often do not recognise health literacy difficulties among working age adults who can engage in spoken conversations in the dominant language [14-16]. Much of the research that has established associations between low functional or health literacy and health sta- tus to date has included several or all of the groups of people whose literacy difficulties are more likely to be recognised and addressed by health services and staff. This may obscure important differences in the ways in which literacy can affect health. Relatively little is known about the implications of low functional or health literacy among those people whose literacy diffi- culties are more hidden. Specific attention to this group may be important to support the development of strate- gies for reducing any adverse health implications of their literacy difficulties. The current review was developed to further our understanding of the relationship between functional or health literacy level and health in a working age popula- tion whose low functional or health literacy skills may be neither obvious nor readily identifiable to health care staff and others. Methods The review sought to establish evidence of associations between low functional or health literacy and health in a working age population whose first language was the dominant language of their country. We considered relationships between measured literacy and health sta- tus, and considered how these might be mediated or moderated by attending as well to relationships between measured literacy and a variety of health-related beha- viours and activities. Review questions The review questions were, for the population of interest: 1. What evidence is there of an association between functional literacy or health literacy level and health status? 2. What evidence is there of an association between functional literacy or health literacy level and the follow- ing potential mediating variables: health promoting or health risk behaviours? access to and use of health services? self-management of health problems? 3. Is there evidence that knowledge of particular health risk or health conditions may mediate the rela- tionship between functional literacy or health literacy and health behaviours?