Discussion
To our knowledge, this is the first scoping review appraising the broad range of health literacy interventions for patients with CAD. Most interventions had a primary focus on building social support for health or on improving the interaction between patients and the health system/health professionals. Key findings were: (1) involving partners in health education can be effective at reducing depression, increasing knowledge and improving physical activity; (2) use of peers for education or support may decrease anxiety, increase self-efficacy and improve health behaviours; (3) the teach-back method helps patients understand information and is associated with reduced hospital readmissions and (4) providing structured follow-up support may improve appropriate use of health services and reduce readmissions.
Evidence for the effectiveness of health literacy interventions among patients with CAD is limited in comparison to systematic reviews in other areas such as health promotion12 or chronic disease.12 40 However, similar to CAD, much of this evidence focuses on functional health literacy only. Use of a conceptual framework in our study has enabled identification of a wider range of studies that go beyond functional health literacy and may be useful in other health conditions to identify characteristics of interventions associated with improved behavioural and clinical outcomes. In relation to types of evidence, two-thirds of the included studies were RCTs, and this is reflected in the relatively large proportion of studies of strong methodological quality.
We found no studies addressing empowerment of people with low health literacy, and a paucity of studies addressing health literacy capacities of health professionals or those facilitating access and appropriate use of health services. We also found heterogeneity between interventions, even within intervention categories, with regards to theoretical basis, recipients of the intervention, duration and frequency of interaction and target outcomes. Outcome measures were equally spread across the health literacy, behavioural and clinical health domains. However, few studies comprehensively covered more than one outcome aspect; therefore, it is difficult to conclude whether health literacy outcomes lead sequentially to behavioural and clinical health outcomes. This is a gap in the literature that limits our knowledge of the potential causal mechanisms and long-term health benefits of health literacy interventions.
Findings from this review suggest that involving partners is an effective way of building social support for health behaviours.19–21 Of note, two of these interventions used a theoretically informed educational approach (the HAPA model), including strategies for engaging family members.19 21 Other studies using this approach in non-CAD populations have also shown improved physical activity,41 and smoking cessation.42 For patients with CAD, the practical and emotional help provided by others can assist with understanding health information and decision-making about management of their condition.43 44 This is aligned with the concept of ‘distributed health literacy’ where patients share tasks of finding, understanding and using health information with others, often drawing on health literacy abilities of others to manage their own health.44 Consideration should, therefore, be given to interventions that build social support systems to assist patients to find, understand and apply health information, including use of proven theoretically based approaches.
Improving partnerships between patients and health providers may also be effective, although of the five studies in this category, we found only two that focused on building patients’ capacity to communicate with healthcare providers.32 33 This is an area for further investigation; for example, a 2017 systematic review found most evidence in healthcare communication is centred on improving the communication skills of providers rather than patients.45 We also found that interventions targeting both providers and patients were effective, including those using teach-back.29 The teach-back method of checking and clarifying information can be considered a health literacy intervention because it helps patients both understand information and recall it later at home. While there is strong evidence for the effectiveness of teach-back in chronic disease populations,46 surprisingly few papers have explored its role among patients with CAD.
We found few studies aiming to build health literacy capacity of health professionals or to empower patients with low health literacy. Some evidence from other settings indicates that interventions among lower health literacy groups are effective at increasing empowerment (eg, telehealth support,47 community health education)48 and these may warrant investigation in patients with CAD. This research should include vulnerable populations in whom health literacy and empowerment are known to be lower.1 Future studies in this area should also consider assessing health literacy using multidimensional tools rather than measuring functional health literacy only.14 Of note, those studies that did assess interventions across different health literacy groups found no difference in effects between patients with lower and higher health literacy; although all three used a functional health literacy instrument.37–39
It is noteworthy that only three studies in this review investigated interventions that incorporated digital technologies. Digital health approaches are progressing rapidly across all fields of medicine, including cardiology. The potential benefit of digital technologies to support heath literacy is manifold, such as equity of access to health-related information, convenient delivery of educational content in different audio-visual formats and languages and the possibility to incorporate user interaction for additional intervention effect.49 At the same time, digital technology interventions must consider the digital health literacy of user groups, that is, the degree to which individuals have the capacity to find, understand, appraise and apply health information from electronic sources.50 This review, therefore, highlights an opportunity for future research to develop and investigate digital health literacy interventions for patients with CAD. In line with key findings from this review, the effectiveness of these digital technologies may be further enhanced by strengthening social support or by targeting patient–provider partnerships.
Strengths and limitations
The strengths of this review include a rigorous methodology and comprehensive search strategy. Scoping reviews are an appropriate method to assess the size and scope of research literature and to identify the nature and extent of research evidence.17 Use of a conceptual framework enabled us to identify a wider range of studies that go beyond functional health literacy and can be used for future systematic reviews. Limitations should also be considered. While we attempted to include only those studies meeting our definition of a health literacy intervention, some studies have multiple mechanisms of effect, not all of which fit into our conceptual framework. As such, we cannot be clear that outcomes were due to the health literacy aspects of the intervention. Searches were limited to published studies, subjecting this review to the possibility of publication bias. Finally, the majority of included studies were conducted in high-income or middle-income countries, and our findings and conclusions may not be relevant for lower income countries where overall literacy of the population may be low, and health systems are poorly resourced. There is limited evidence describing health literacy in low-income countries, including in cardiac conditions. A recent systematic review51 identified that health literacy interventions in low-income and middle-income countries were primarily functional in nature, i.e., focused on improving knowledge and understanding at the individual level—there was less emphasis on the role of health services and systems in addressing health literacy barriers. Further research in low-income and middle-income countries is required that incorporates individual and system-level factors; however, it is important that this is locally driven with an understanding of contextual factors.52