The combination of the key words with the three search terms resulted in the initial identification of 170 publications. Additional publications were found by reference tracking and included in the review. Based on the application of the inclusion criteria to the abstracts, 19 publications were retrieved which explicitly dealt with the definition of health literacy, and 12 with conceptual frameworks of health literacy.
Definitions of health literacy
From the 19 publications focusing specifically on definitions of health literacy 17 explicit definitions could be derived (Table ). Of these definitions, the ones by the American Medical Association [12
], the Institute of Medicine [8
] and WHO [31
] are cited most frequently in the eligible literature. A shared characteristic of these definitions is their focus on individual skills to obtain, process and understand health information and services necessary to make appropriate health decisions. However, recent discussions on the role of health literacy highlight the importance of moving beyond an individual focus, and of considering health literacy as an interaction between the demands of health systems and the skills of individuals. In fact the Institute of Medicine report already alluded that "health literacy is a shared function of social and individual factors, which emerges from the interaction of the skills of individuals and the demands of social systems" [8
]. More recently, Kwan [32
] and Pleasant [33
] underscored the importance of skills and abilities on the part of all
parties involved in communication and decisions about health, including patients, providers, health educators, and lay people. This broader view is presented in the definition proposed by Zarcadoolas, Pleasant and Greer [34
], who state that a health literate person is able to apply health concepts and information to novel situations, and to participate in ongoing public and private dialogues about health, medicine, scientific knowledge, and cultural beliefs. Freedman and her collegues [35
] argue that the medical perspective on factors influencing people's health should be shifted towards a societal level, and that a distinction must be made between public and individual health literacy. Public health literacy can be found when the conceptual foundations of health literacy are in place in a group or community.
Definitions of health literacy
The content analysis on the definitions yielded six clusters representing: (1) competence, skills, abilities; (2) actions; (3) information and resources; (4) objective; (5) context; and (6) time as outlined in Table . Accordingly each cluster was carefully examined, discussed and condensed by the research team and the resulting chosen terms and notions were combined to yield a new 'all inclusive' comprehensive definition capturing the essence of the 17 definitions identified in the literature:
The six clusters identified when condensing the definitions from the literature review
Health literacy is linked to literacy and entails people's knowledge, motivation and competences to access, understand, appraise, and apply health information in order to make judgments and take decisions in everyday life concerning healthcare, disease prevention and health promotion to maintain or improve quality of life during the life course.
This definition encompasses the public health perspective and can easily be specified to accommodate an individual approach by substituting the three domains of health "healthcare, disease prevention and health promotion" with "being ill, being at risk and staying healthy".
An integrated conceptual model of health literacy
Whereas a number of conceptual models of health literacy have been presented in the literature, none of these can be regarded as sufficiently comprehensive to line up with the evolving health literacy definitions and with the competencies they imply [59
]. This is probably due to the fact that attempts to conceptualize health literacy have thus far failed to integrate the existing knowledge encompassing different perspectives on health literacy. Firstly, most of the existing conceptual models are not sufficiently grounded in theory in terms of the notions and concepts included. Secondly, very few models have integrated the components included in "medical" and "public health" literacy models. The only models which explicitly try to bridge the difference between both views are Nutbeam's [36
] and Manganello's [50
], whose dimension of functional literacy corresponds with the cognitive skills of medical health literacy. Thirdly, while acknowledging that health literacy entails different dimensions, the majority of the existing models are rather static and do not explicitly account for the fact that health literacy is also a process, which involves the consecutive steps of accessing, understanding, processing and communicating information. Fourthly, while most conceptual models identify the factors that influence health literacy and mention its impact on health service use, health costs and health outcomes, the pathways linking health literacy to its antecedents and consequences are not very clear. Researchers could link conceptual models of health literacy more explicitly to established health promotion theories and models [59
]. Finally, very few conceptual models of health literacy have been empirically validated. To address these shortcomings, we propose an integrated model of health literacy which captures the main dimensions of the existing conceptual models reviewed above (Figure ).
Integrated model of health literacy--see separate file.
The model combines the qualities of a conceptual model outlining the main dimensions of health literacy (represented in the concentric oval shape in the middle of Figure ), and of a logical model showing the proximal and distal factors which impact on health literacy, as well as the pathways linking health literacy to health outcomes.
The core of the model shows the competencies related to the process of accessing, understanding, appraising and applying health-related information. According to the 'all inclusive' definition this process requires four types of competencies: (1) Access
refers to the ability to seek, find and obtain health information; (2) Understand
refers to the ability to comprehend the health information that is accessed; (3) Appraise
describes the ability to interpret, filter, judge and evaluate the health information that has been accessed; and (4) Apply
refers to the ability to communicate and use the information to make a decision to maintain and improve health. Each of these competences represents a crucial dimension of health literacy, requires specific cognitive qualities and depends on the quality of the information provided [60
]: obtaining and accessing health information depends on understanding, timing and trustworthiness; understanding the information depends on expectations, perceived utility, individualization of outcomes, and interpretation of causalities; processing and appraisal of the information depends on the complexity, jargon and partial understandings of the information; and effective communication depends on comprehension. The competences also incorporate the qualities of functional, interactive and critical health literacy as proposed by Nutbeam [36
This process generates knowledge and skills which enable a person to navigate three domains of the health continuum: being ill or as a patient in the healthcare setting, as a person at risk of disease in the disease prevention system, and as a citizen in relation to the health promotion efforts in the community, the work place, the educational system, the political arena and the market place. Going through the steps of the health literacy process in each of these three domains equips people to take control over their health by applying their general literacy and numerical skills as well as their specific health literacy skills to acquire the necessary information, understanding this information, critically analyzing and appraising it, and acting independently to engage in actions overcoming personal, structural, social and economical barriers to health. As contextual demands change over time, and the capacity to navigate the health system depends on cognitive and psychosocial development as well as on previous and current experiences, the skills and competencies of health literacy develop during the life course and are linked to life long learning.
The frameworks associated with the three domains represent a progression from an individual towards a population perspective. As such, the model integrates the "medical" conceptualization of health literacy with the broader "public health" perspective. Placing greater emphasis on heath literacy outside of healthcare settings has the potential to impact on preventative health and reduce pressures on health systems.
The combination of the four dimensions referring to health information processing with the three levels of domains yields a matrix with 12 dimensions of health literacy as illustrated in Table .
The matrix with four dimensions of health literacy applied to three health domains
Four dimensions of health literacy in the domain of healthcare, i.e., the ability to access information on medical or clinical issues, to understand medical information, to interpret and evaluate medical information, and to make informed decisions on medical issues and comply with medical advice.
Four dimensions of health literacy in the domain of disease prevention, notably the ability to access information on risk factors for health, to understand information on risk factors and derive meaning, to interpret and evaluate information on risk factors, and to make informed decisions on risk factors for health.
Four dimensions in the domain of health promotion, notably the ability to regularly update oneself on determinants of health in the social and physical environment, to comprehend information on determinants of health in the social and physical environment and derive meaning, to interpret and evaluate information on determinants, of health in the social and physical environment, and the ability to make informed decisions on health determinants in the social and physical environment.
Health literacy is in our understanding regarded an asset for improving people's empowerment within the domains of healthcare, disease prevention and health promotion.
In addition to the components of health literacy proper, the model in Figure also shows the main antecedents and consequences of health literacy. Among the factors which impact on health literacy, a distinction is made between more distal factors, including societal and environmental determinants (e.g., demographic situation, culture, language, political forces, societal systems), and proximal factors, which are more concerned with personal determinants (e.g., age, gender, race, socioeconomic status, education, occupation, employment, income, literacy) and situational determinants (e.g. social support, family and peer influences, media use and physical environment). Health literacy is strongly associated with educational attainment [50
], as well as with overall literacy [34
]. Fundamental literacy affects a wide range of cognitive, behavioral, and societal skills and abilities. It should be distinguished from other specific literacy, such as science literacy (i.e., the ability to comprehend technical complexity, understanding of common technology, and an understanding that scientific uncertainty is to be expected), cultural literacy (i.e., recognizing and using collective beliefs, customs, world-views, and social identity relationships) and civic literacy (i.e., knowledge about sources of information and about agendas and how to interpret them, enabling citizens to engage in dialogue and decision-making). According to Mancuso [43
], an individual must have certain skills and abilities to obtain competence in health literacy, and identifies six dimensions that are considered as necessary antecedents of health literacy, namely operational, interactive, autonomous, informational, contextual, and cultural competence.
Health literacy in turn influences health behavior and the use of health services, and thereby will also impact on health outcomes and on the health costs in society. At an individual level, ineffective communication due to poor health literacy will result in errors, poor quality, and risks to patient safety of the healthcare services [61
]. At a population level, health literate persons are able to participate in the ongoing public and private dialogues about health, medicine, scientific knowledge and cultural beliefs. Thus, the benefits of health literacy impact the full range of life's activities--home, work, society and culture [34
]. Advancing health literacy will progressively allow for greater autonomy and personal empowerment, and the process of health literacy can be seen as a part of an individual's development towards improved quality of life. In the population, it may also lead to more equity and sustainability of changes in public health. Consequently, low health literacy can be addressed by educating persons to become more resourceful (i.e., increasing their personal health literacy), and by making the task or situation less demanding, (i.e., improving the "readability of the system").