Review question/objective

The overall objective of this systematic review is to identify and synthesize the best available evidence on the effectiveness of health literacy interventions in socioeconomically disadvantaged people living in the community to improve health-related outcomes.

More specifically, the objectives of this systematic review are to identify and synthesize evidence on the effectiveness of single or complex health literacy interventions in enabling socioeconomically disadvantaged people living in the community to access, understand, appraise and apply health information.

Background

Literacy is "the capacity to read, write and have basic numeric skills",1(p291) allowing people to effectively function and participate in society.1 Approximately 25% of the adult population in the world are illiterate or have poor literacy skills.1 Low literacy levels are associated with a variety of adverse health outcomes.2 In addition to the literacy skills required to adequately function in everyday life, the notion of literacy has expanded to health literacy (HL) in order to effectively function in the healthcare system. "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".3(p3) Health literacy is a relatively new concept introduced for the first time in the 1970s, and has been discussed in many studies over the last two decades. The HL concept has many implications in health care, health education and health promotion,4 and is strongly correlated with the social determinants of health, health behaviors and health outcomes.3 Therefore, HL is today considered as one of the most important issues in healthcare and in public health,3-5 and is thus increasingly addressed in current health and social policies.

Health literacy: a public health concern

Today, each individual is confronted, at some point, with multiple health issues and decisions.6 Society and healthcare systems are becoming more complex.5,7 Consequently, requirements in literacy and optimal use of health information have become more and more important5 for maintaining good health status. Increasingly, citizens are asked to take an active part in health decisions7 and to become "informed patients".6 To navigate this new healthcare environment,7 many abilities and skills are needed, such as information-seeking, communication, critical thinking and problem-solving.3 A good level of HL appears to positively influence health and the ability to effectively navigate in the healthcare system, as shown by cross-sectional studies, via better choices and sound health decisions, more active involvement in discussions with health professionals,8-10 greater self-efficacy,11-15 better abilities in self-care,15 adoption of positive health behaviors,16-19 increased prevention,20-22 better health outcomes,16 social capital development,6 and lower healthcare costs.23 We can therefore consider that good levels of HL contribute to improved global health in the general population.24 According to a national study,25 nearly half of the adult American population shows a low or marginal level of functional HL, particularly among socially and socioeconomically disadvantaged groups. Similarly, in Europe, almost half of the population has limited HL.26 Due to poor understanding of health messages,27 low HL skills are associated with a variety of adverse health effects:16 increased mortality,16,20 poorer self-reported health status,28-32 greater use of emergency services but less use of preventive services, higher rates of chronic diseases and adoption of adverse health behaviors (smoking, consumption of alcohol and illicit products, sedentary lifestyles),33 which lead to higher healthcare costs.5,7,20,28,29 Given the significant number of consequences of a low HL level, the importance of the HL issue is increasingly discussed in health policies in Europe, and HL has been recognized as a priority within the Strategy of the European Commission 2008-2013.3,34 A public health imperative,6 HL is also considered as an important predictor of health status and health behaviors in the general population,31 and is recognized as a major determinant of health by the World Health Organization (WHO).35 Therefore, HL is a key public health issue1 and must take a central place in future research, action and health policy debates.6

Health literacy dimensions and health literacy skills

To promote and maintain good health, to function effectively in the healthcare context and to enable people to act on their health condition, a set of skills or competencies is required. From this perspective, HL can be considered as a "constellation of skills" or as a multidimensional concept.3,36

To describe the skills that are essential to function effectively in the health system, Sorensen et al.3 proposed an integrative conceptual model of HL. This model focuses on the three domains of the health continuum (health care, disease prevention and health promotion), and both clinical and community settings are considered. Besides basic reading and writing skills needed in everyday situations to function and participate effectively in society,37 defined as functional literacy by Nutbeam,3 four types of competencies, each representing an essential dimension of HL, are required in order to navigate the health continuum: "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".3(p9) Progressing on these four levels allows people to acquire a multitude of social, personal and cognitive skills that are essential for a greater control on one's own health,6 and "to exert greater control over life events and situations".4(p264) Therefore, HL "is not simply a set of functional capabilities" such as reading, writing and numeracy skills,37(p2075) but a wide range of complementary skills and competencies that can be built. However, HL does not impact health directly.11,12,38-40 Health literacy levels influence some health promotion or health education constructs, such as specific health related knowledge, self-care, self-management, self-efficacy, problem-solving skills, decision-making skills and empowerment.38,11,12,40 These can be considered as proxy outcomes of a HL process and suggest that different ways exist to operationalize the HL concept in interventions. These interventions can take many forms, such as education and disease management interventions, interventions aiming at improving patient-provider communication, interventions aiming at improving access to health information, and interventions for improving usability of healthcare systems and services. Therefore, proxy measures of the impact of HL on health-related outcomes need to be assessed.

The clinical approach and the public health approach of health literacy

Two complementary HL approaches can be distinguished: the "clinical" approach and the "public health" approach.41,42 In the clinical approach, HL represents the necessary skills needed to navigate in a clinical setting and often include aspects such as selecting care providers,43 understanding and completing consent forms,1,43 and understanding medicine labels, how to take medication,1,43 oral information given by health professionals,1 and how to manage the disease.43 In this context, HL is considered a construction at the individual or patient level,41 and the focus is on the "therapeutic dyad" patient-healthcare provider.41 From this clinical perspective, HL strategies should focus primarily on the effectiveness of clinical care. Health literacy interventions mainly focus on the improvement of HL skills and on the adaptation of health communications at the patient level41 in people with low HL levels and related to patient education.

To extend the HL concept to the community setting, the "public health" approach, introduced by Freedman in 2009, was developed41 to incorporate social and environmental factors, and other determinants of health causing low levels of HL among populations. Public health literacy is defined as "the degree to which individuals and groups can obtain, process, understand, evaluate, and act upon information needed to make public health decisions that benefit the community".41(p448) From this public health perspective, HL can be considered as a tool, an asset or a means for individuals to exert a greater control and to act on all personal, social and environmental factors that determine health, thus reflecting a health promotion orientation.37 In this respect, this perspective can be operationalized across the continuum of strategies in health care, prevention, health education and health promotion.41 Therefore, public health literacy is a comprehensive HL conceptualization, and public health literacy interventions need to be assessed for their effectiveness.

The mediating role played by health literacy between socio-economic status (SES) and health outcomes and health disparities

Some demographic and social factors, such as social status and socioeconomic situation (educational attainment, occupation, income),4,12,26 social support,3,12 culture and language,3 and some personal characteristics (e.g. age,3,29,42 gender,3,28 race and ethnicity),3,28,33 influence HL skills and are thus considered as antecedents of HL.3,16 These can have a positive impact on HL and promote good levels of HL. Conversely, antecedents can also negatively impact HL (e.g. low level of educational attainment, disadvantaged socioeconomic status, belonging to a minority group, immigration), thereby becoming risk factors for low HL levels. Considering the relationship between SES and HL level, it is not surprising to notice that the weakest health-related skills are found among the most disadvantaged socioeconomic groups. Advantaged social and socioeconomic groups are those placed on the higher levels of the social hierarchy, and thus tend to have greater HL skills. Conversely, disadvantaged social and socioeconomic groups are those at the bottom of the social ladder, with a lack of material resources44 lower educational attainment, and less desirable or underpaid profession. In a HL context, the socially and socioeconomically disadvantaged are those at risk of low HL levels. Thus, different HL levels contribute to health disparities.22 A health disparity is defined as differences in health status and health outcomes45,46 between social groups "that is not only unnecessary and avoidable, but in addition, are considered unfair and unjust".46(p219) A health disparity includes differences that occur through age, gender, race/ethnicity, education, income, disability, geographic location, sexual orientation or religion,47 and which systematically and adversely impact socially and economically disadvantaged groups.44,45 The HL level then becomes a modifiable risk factor for health disparities on which it is possible to act to reach greater health equity. Therefore, ways to improve health status and reduce disparities among disadvantaged people through HL strategies need to be further explored.42,48

Existing systematic reviews

A search was undertaken in databases such as the Cochrane Database of Systematic Reviews, Best BETS, Campbell Collaboration and the Joanna Briggs Institute Database of Systematic Reviews and Implementation Reports, as well as PubMed which found that there are no quantitative systematic reviews that examine HL interventions to improve health-related outcomes among socioeconomically disadvantaged groups. One systematic review focused on the relationship between HL, numeracy and health outcomes in the diabetes population.49 This review shed light on certain HL proxy measures, such as knowledge, self-efficacy, self-care and self-monitoring, but there was not enough consistent evidence showing that HL levels were associated with diabetes-related outcomes. Two systematic reviews50,51 on the effectiveness of interventions in improving health-related outcomes of people with limited or low literacy only considered HL as the ability to read, write and use numbers effectively, and did not address HL as a broader concept. One systematic review52 measuring interventions to mitigate the effects of low HL and to improve health outcomes and use of healthcare services may be relevant to the topic of this proposed review, but it did not address the public health approach of HL and hence was not within the scope of this review. One systematic review53 on the effectiveness of interventions in primary healthcare and in the community to improve HL in adults and to promote positive change in lifestyle behavior did not refer to disadvantaged groups. The author had called for the inclusion of these groups in future HL studies.

This proposed systematic review will aim to identify and synthesize the best available evidence on HL interventions in the community, and allow a better understanding of the conditions for which effective HL interventions aimed at improving health-related outcomes in socioeconomically disadvantaged people can be implemented. This will enable the development of an intervention aiming at reducing health disparities based on a comprehensive HL strategy. This review will therefore address all dimensions and components of HL and shed light on interventions that can positively influence health outcomes and reduce health disparities.

Inclusion criteria

Types of participants

This review will consider studies that include adults aged 18 years or over, male and female, of any ethnicity and cultural group, and who are socially or socioeconomically disadvantaged in the community.

PROGRESS factors, including Place of residence, Race/ethnicity - culture - language, Occupation, Gender, Religion, Education, Socio economic status, Social capital or age,54 will serve to identify "disadvantaged" people and social groups. These are "socially stratifying factors that drive variations in health outcomes"54(p58) and contribute to disparities in health. For example, people living in rural areas, from a minority group, with low education or low income,26 are considered as disadvantaged and are at risk of health disparities. In this review, studies considering any or several of these factors will be considered for inclusion. In this review, studies conducted in any community setting will be considered, such as community centers, community preventive services, community-based health promotion settings, community healthcare facilities, primary healthcare centers, homes or worksite settings.

Exclusion criteria: studies involving children aged under 18 years, studies involving people living in nursing or other institutional living facilities, studies involving people with cognitive impairments or dementia, for whom HL - or one of its components - is difficult to measure or evaluate, studies targeting healthcare professionals (e.g. physician, nurse, etc.), studies targeting non-health professionals (e.g. community workers, social workers, etc.), and studies which do not give an indication of the socioeconomic status will be excluded

Types of intervention(s)/phenomena of interest

This review will consider studies focused on the following interventions:

1) Those that target HL according to a clinical approach (in a clinical setting, at the patient or individual level) and/or a public health approach (in a community setting, at the population level), any of its dimensions, and operationalized by any healthcare, prevention, education or health promotion strategy.

2) Those delivered at the individual/intrapersonal level, which encompass characteristics and personal factors of an individual, such as knowledge, skills, lifestyles, behavior and attitudes55,56 (such as education interventions and disease management interventions); the interpersonal level, including social interactions, social influences and social support55-57 (such as interventions aimed at improving patient-provider interaction/communication); the community level, with a focus on populations, groups and organizations, and including social and physical environments considered to have an impact on health outcomes55,58 (such as interventions aimed to improve access to accurate and appropriate health information); or at the societal level, including economic, social, educational and health policies55 (such as interventions for improving usability of a healthcare system and health services).

3) Those delivered by any healthcare or social work professional from healthcare system or out of the healthcare system, such as physician, nurse, community worker or social educator with a professional degree recognized in the country where the intervention takes place.

4) Those that are either single strategy or complex interventions. Exclusion criteria: studies concerning general literacy (e.g. reading, writing and calculating) will be excluded.

Types of comparison

This review will consider studies that offer no comparison, a passive comparison (such as no treatment, standard care), or an active comparison (such as variation of the intervention).

Types of outcomes

This review will consider studies that include the following outcome measures, based on the Outcome Model for Health Promotion4 and informed by the Outcomes of Interest to the Cochrane Consumers and Communication Review Group,59 but are not limited to:

Primary outcomes: those considered as final outcomes of a HL process, that is, outcomes related to the capacity to apply health information in order to promote and maintain good health, such as: 1) health-related quality of life and health-related outcomes (general health status, perceived health status, wellbeing, life expectancy, morbidity, mortality, disability); 2) health behaviors (self-efficacy, healthy life styles and preventive health practices, compliance/adherence and behavior change); and 3) access and use of healthcare services (preventive service use, office visits, hospitalizations).

Some examples of measurement tools for the primary outcomes include: Health Status: Short-Form-36 Health Survey,60 Quality of life: the EuroQol,61 Wellbeing: the Satisfaction with Life Scale,62 Self-efficacy: the Self-Efficacy Scale,63 Disability: the OECD Long-Term Disability Questionnaire,64 Health-related behaviors: the Health Promoting Lifestyle Profile,65 and access to healthcare services: Unmet Needs for Healthcare indicators.66

Secondary outcomes: those leading to the application of health information, comprising basic level of HL and other components of a HL process, such as: 1) functional HL (reading, writing and numeracy skills) as a prerequisite for more advanced HL skills (accessing, understanding, appraising and applying health information); 2) knowledge and understanding: information access and use, health-related knowledge acquisition, participant satisfaction with the information provided or received; 3) communication: communication enhancement, communication skills; 4) participant decision-making: (shared) decision-making process, decision made, satisfaction with the decisions made; 5) support: social interactions, social support, help-seeking behavior; 6) skills acquisition: self-care and self-management skills, self-monitoring, self-advocacy, self-learning skills, social skills, coping skills, empowerment skills, critical thinking, problem-solving ability, and navigation skills; 7) predisposing factors of health behavior change: attitudes, beliefs, intent to change health behavior; and 8) other relevant outcomes.

Exclusion criteria: studies that used cognitive impairment or dementia as an outcome of interest, studies considering HL levels as an outcome, and studies on cost-effectiveness outcomes of HL interventions will be excluded.

Types of studies

This review will consider any experimental study design including randomized controlled trials, non-randomized controlled trials, and quasi-experimental studies for inclusion.

Search strategy

The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of MEDLINE and CINAHL will be undertaken followed by an analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Thirdly, the reference list of all identified reports and articles will be searched for additional studies. A hand search of relevant journals not included in electronic databases will also be conducted. Studies published in any language will be considered for inclusion in this review. Assessment for inclusion of papers in languages other than Romance languages (e.g. Spanish, French, Portuguese, Italian) and Germanic languages (e.g., English, German, Dutch) will be based on the English language abstracts where available. Relevant studies will be translated into English. No date limits will be imposed on database searching. The search in CINAHL will be performed to filter out articles also published in PubMed. Individual search strategies will be developed for each database to take into account the differences in Thesaurus terminology and indexing. Titles and abstracts of studies retrieved in the search will be assessed for relevance against the inclusion and exclusion criteria. Bibliographic details of the studies will be downloaded or manually entered into the references management database, Endnote X7.

The databases searched will include: Pubmed, CINAHL, the Cochrane Central Register of Controlled Trials (CENTRAL), Embase, ERIC, PsycINFO, TRoPHI, and Web of Science.

The search for grey literature and unpublished studies will include clinical trial registers, technical and official rapports from government or academic institutions, conference papers and proceedings, theses and dissertations, and an internet search of Doaj, Google, Google Scholar, Mednar, Worldcat, ProQuest, and Scopus. The databases searched for clinical trial registers will include: Clinical Trials.gov, EU Clinical Trial Register, Current Controlled Trials (CCT), and UK Clinical Trials Gateway. The databases searched for theses and dissertations will include: ProQuest Dissertations & Theses Global (PQDT Global) and DART-Europe E-theses portal.

Initial keywords to be used will be:

1) Health Literacy, public Health Literacy, health competences, health illiteracy;

2) Social characteristics, vulnerable populations [MeSH], minority groups, social inequities, social disparities, social class [MeSH], socioeconomic status; Socioeconomic Factors [MeSH], disadvantaged.

3) Health status [MeSH], health disparities outcomes, community health outcomes, health behavior [MeSH], health status disparities [MeSH], Health Literacy outcomes.

A PRISMA flow diagram will be used to summarize the study selection process. It will include the total numbers of studies identified and screened from all databases included in the review and from hand searches, studies assessed for eligibility, studies included in the review, and studies excluded from the review with reasons for exclusions.67

Assessment of methodological quality

Quantitative papers selected for retrieval will be assessed independently by two reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion, or with a third reviewer. For inclusion in the review, reviewers agree that studies must meet any of the seven out of ten methodological assessment criteria.

Data extraction

Upon agreement between the reviewers, quantitative data will be extracted from papers included in the review using the standardized data extraction tool from JBI-MAStARI for experimental studies (Appendix II). The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. Authors of quantitative primary studies will be contacted for missing information or to clarify unclear data.

Data synthesis

Quantitative data will, where possible, be pooled in statistical meta-analysis using JBI-MAStARI. All results will be subject to double data entry. Effect sizes expressed as odds ratio (OR) for categorical data and weighted mean differences (MD) for continuous data and their 95% confidence intervals will be calculated for analysis. Heterogeneity will be assessed statistically using the standard Chi-square. In the absence of clinical and statistical heterogeneity, a fixed-effect model will be applied to pooled data. In the presence of statistical heterogeneity, a random effects model will be applied for meta-analysis. Subgroup analysis, based on the different quantitative study designs, types of intervention included in this review, and population differences, will be used to explore variations in treatment effects. Where statistical pooling is not possible, the findings will be presented in narrative form including tables and figures to aid in data presentation where appropriate.

Conflicts of interest

We declare that there are no conflicts of interest.

References