The term health inequality refers to the unjust nature of health differences between social groups, generated by social conditions, describing the pattern in which those from economically and socially poorer backgrounds run higher risks of premature death and contracting chronic or serious illness [
1]. As such, health is costly to individuals, societies, and economies [
2]. In parallel, health literacy is now well-established as a modifiable factor that contributes to the promotion and maintenance of good health and wellbeing across the life course. The importance of health literacy is increasingly recognised due to both the prevalence of low health literacy and the associations between low health literacy and poorer health, unhealthy behaviours, and higher rates of healthcare utilization [
3]. Globally, there has been a sustained growth in efforts to measure and monitor health literacy at a population level, to understand how health literacy is distributed within populations, to understand the consequences of this distribution for population health, and ultimately to inform public health policies and strategies. Health literacy follows a socio-economic gradient [
3], as do health outcomes [
4] and health behaviours [
5]. In order to better understand these interrelationships, this study aims to examine the impact of socio-economic position on the health literacy distribution of health status and outcomes in the Irish population. The goal of this study is to investigate the extent to which increasing health literacy may improve health outcomes and behaviours and to compare the effects of increasing health literacy at different levels of social status. It is intended that the results of this study will serve to inform a health-literacy approach to the design and monitoring of public health interventions in Ireland and elsewhere and may contribute to enhancing their efficiency and effectiveness.
Although life expectancy in Ireland has increased, there is evidence to suggest that people are not necessarily ageing in good health—noncommunicable diseases, such as hypertension and obesity, are increasingly common [
6]. It has been estimated that approximately 5400 deaths per year in Ireland could be prevented if social inequalities in health were addressed and that this would involve detailed consideration of three influential factors: the distribution of income and government spending, psychosocial factors, such as stress and social support, and lifestyle or behavioural factors associated with different socio-economic statuses [
1]. These factors interrelate and affect one another through the experience of poverty, leading to the substantial health gap between those of higher and lower socio-economic status [
7]. The conditions of poverty can also contribute to worsened health, for example, chronic respiratory issues from living in damp housing or limited access to education and employment [
1]. Addiction issues, such as smoking, alcohol, and drugs also disproportionally affect those from less affluent socio-economic backgrounds, exacerbating and creating additional chronic conditions such as high blood pressure and increasing the mortality rate due to smoking, drinking, and drug-related deaths. Mental health is also an issue, as there are higher rates of depression and hospitalisation among lower socio-economic classes in Ireland, often due to the mental health effects of poverty, systemic inequality, and material deprivation [
8].
Analysis of health policy in Ireland suggests that the approach is attuned to the impact of poverty and inequality on health. However, limitations in current policies surrounding healthcare provision have been described as being underequipped to deal with more “unpredictable” factors, such as the onset of illness and disability [
9], which place significant demands on individuals in terms of health literacy. Evidence from a European survey “Health Inequalities in Europe: Setting The Stage for Progressive Policy Action” [
10] suggests that Ireland’s two-tiered healthcare system may also contribute to the gap of health inequity, insofar as a proportion of the population on low incomes are above the income threshold of entitlement for the General Medical Scheme (GMS), pay out-of-pocket for medical expenses, and cannot afford private medical insurance [
10,
11]. This report also noted that Ireland is one of the only countries in the European Union without universal healthcare coverage for all citizens [
10], and this is now a key focus of the Sláintecare reform. It is clear that the health and social care system in Ireland is complex and, like many countries, also presents a particular challenge in terms of health literacy and public health, insofar as those most in need are also those who are likely to lack the health literacy skills to navigate the system and engage fully in programmes and interventions to improve health and wellbeing.
1.1. Health Literacy in Ireland
Health literacy is a broad concept. Functional health literacy refers to reading and writing capacities that assist in everyday health concerns, interactive health literacy refers to the ability to apply one’s knowledge of health and wellbeing to new circumstances, and critical health literacy refers to the ability to think critically and analyse health information objectively [
12]. Low levels of health literacy can have serious negative health outcomes, such as an inability to identify and access information on illness, and to communicate about illness, conditions, or pain. Low levels of health literacy have been directly linked to higher rates of negative health outcomes, poor disease knowledge, low levels of preventive health service utilisation, lower levels of mental wellbeing, low medication adherence and earlier death, and poorer healthcare interactions [
13,
14].
The European Health Literacy Survey (HLS-EU), which took place in eight EU countries including Ireland, showed that the mean overall prevalence of inadequate or problematic health literacy was 47.6%, with Ireland having a slightly lower prevalence of 40% [
3]. A financial, age, education, and social status gradient was also observed. These results confirmed the results of studies undertaken elsewhere, showing an association between inadequate or problematic health literacy and lower self-rated health and higher rates of chronic health conditions [
3,
15]. Further, the HLS-EU showed that people with inadequate and problematic health literacy and a chronic health condition found their health condition more limiting and had higher rates of healthcare utilization [
3]. The HLS-EU showed associations between health literacy and self-reported physical exercise, self-reported body-mass index (BMI), and alcohol intake but no consistent association with smoking [
3].
Whilst international data are helpful in setting the international context, it is important to undertake national-level analyses. As an example, analysis of Irish HLS-EU data confirmed the international findings of the financial, age, education, and social status gradients of health literacy [
14], as well as the association between health literacy and exercise [
16,
17], but found no association between health literacy and BMI and alcohol intake [
16]. Another difference from the international findings was a significant association between health literacy and smoking in the Irish data [
16].
In terms of health policies, health literacy is now widely recognised as an important factor in improving health behaviours, enhancing self-management skills, improving health outcomes, addressing health inequalities, and as a lever for preventing and controlling noncommunicable diseases (NCDs). A recent evidence synthesis identified 46 existing and/or developing health literacy policies at international, national, and local levels in 19 of the 53 Member States of the World Health Organisation (WHO) European Region (36%) [
18].
Ireland, like many countries across the WHO region, is actively engaged in the WHO European Action Network on Health Literacy for Prevention and Control of NCDs [
19] and the Measurement of Population and Organisational Health Literacy (M-POHL) Consortium to strengthen evidence-for-policy measuring, in terms of population and organisational health literacy [
20]. In terms of national health policies, strengthening health literacy in Ireland features in multiple health policies [
8,
21,
22].
Like many other countries, at service level in the Irish healthcare system and in terms of health communication, there continues to be widespread recognition of the several main barriers to health literacy as outlined by Zarcadoolas et al. [
23]: complexity of written information in print and on the web; lack of health information in languages other than English; lack of cultural appropriateness of health information; inaccuracy and/or incompleteness of information available through mass media; prevalence of low literacy and numeracy in the population, and among particular cohorts and groups, a lack of empowering content that targets behaviour change. Therefore, it is important to consider the extent to which, in recent years, health service providers and the national health service in Ireland (the Health Service Executive, HSE) have taken a comprehensive and multifaceted approach to overcoming the barriers to health literacy. For example, the current HSE communication strategy [
24] promotes the use of plain English in all written material, champions the provision of credible online and published sources of information, supports targeted information campaigns, and messages and directs information to specific cohorts and groups, adopting behavioural insights in communication with patients and citizens [
25]. In addition, the importance of adapting material to respond to known low literacy and numeracy proficiency levels in the population and particular cohorts is well recognised, and this is complimented by efforts to promote good health literacy practices in the delivery of primary and community health services, for example, through the National Adult Literacy Agency’s unique ‘Crystal Clear’ quality mark for pharmacists and general practitioners [
26].
1.2. Health Literacy and Socio-Economic Status
A critical motivation for this study is the evidence that low health literacy is not evenly distributed across society. There is a marked social gradient; people from lower socio-economic groups are more likely to have low health literacy [
3,
15,
27]. Furthermore, functional health literacy may serve as a pathway by which low Socio-Economic Status (SES) affects health status [
28]. An integrative review by Stormacq et al. showed that health literacy mediates the relationship between SES and health status, quality of life, specific health-related outcomes, health behaviours, and use of preventive services [
29]. The authors hypothesise that health literacy can be considered as a modifiable risk factor of socioeconomic disparities in health and that enhancing the level of health literacy in the population or making health services more accessible to people with low health literacy may be a means to reach a greater equity in health [
29].
There is also a well-described social gradient in chronic conditions, such as diabetes [
30], cardio vascular disease [
31], and chronic obstructive pulmonary disease [
32], in adverse lifestyle choices [
5], health care utilization [
33], and self-rated health [
34].
There is evidence from the UK that public health interventions have tended to have more impact in higher socio-economic groups, thus tending to widen health inequalities [
5]. The presence of social gradients in health literacy, however, means that health literacy interventions may reduce rather than exacerbate health inequalities. Increasingly, effective interventions are being developed to build health literacy skills in socio-economically disadvantaged groups as well as improving healthy behaviours [
35,
36,
37,
38].
Building on this evidence, and the hypotheses put forward by Stormacq et al. [
29], there are two hypotheses explored in this study:
- 1
Increases in health literacy for people in lower social status groups are associated with a greater increase in health outcomes and healthy lifestyle behaviours than for those in middle and upper groups.
- 2
Increases in health literacy for people in lower social status groups are associated with a greater reduction in healthcare utilisation than for those in middle and upper status groups.
The aims of this study were thus to investigate, using a population health perspective:
- 1
The extent to which increasing health literacy may improve health outcomes and behaviours.
- 2
The potential effects of increasing health literacy at different levels of social status.