Social determinants of neurological disease: tackling inequalities

The importance of social determinants of health and disease has historically been understudied, despite their wide-ranging impact; however, the COVID-19 pandemic has brought the significance of these factors to the fore. Multiple factors—including, poverty, educational level, geography, race, and gender—are associated with variation in disease outcomes (figure ). In the Marmot review, published in February 2010, socioeconomic deprivation was linked with many adverse health outcomes, ranging from childhood dental caries to cancer mortality. Despite publication of this report, the way that social inequalities cause or affect disease, and potential interventions to address these factors, have not been well studied.

Figure.

Social determinants of health are the conditions in which people are born, grow, live, work, and age

Evidence is mounting to show that neurological diseases are no exception to the effects of social determinants. For example, in England and Wales in 2017, 14 837 (21%) dementia deaths were attributable to socioeconomic deprivation. Yet, deprivation and other social determinants were not included as risk factors in the 2020 update to the Lancet Commission on dementia prevention, intervention and care. There are many pathways by which social determinants might affect brain health, and these routes influence all stages of disease risk and trajectory. Aside from their effect on access to health care and diagnostic services, social determinants could be important modulators of disease biology, either directly or indirectly through influences on lifestyle risk factors and comorbidities. Moreover, rapid adoption of innovations to deliver services remotely and a push towards self-monitoring, patient-initiated follow-up, and self-management are factors that could potentially widen health inequalities.

Multidisciplinary approaches are required to further our understanding of these issues in neurological disease, with the aim of ultimately making research and health care relevant to all. On Nov 25, 2021, the Preventive Neurology Unit at the Wolfson Institute of Population Health (Queen Mary University London, London, UK) hosted a symposium on inequalities and social determinants of health, with a particular focus on lessons for neurology. The aims of the symposium were to increase awareness of these topics for researchers, clinicians, and funders, and to generate new research ideas for equity and inclusivity.

For the past 40 years, the field of HIV has been at the forefront of research into health inequalities, and neurologists have much to learn from this experience and expertise. Vanessa Apea (Barts Health NHS Trust, London, UK) started the symposium by highlighting that, despite striking improvements in the management of HIV, there remain disparities in outcomes across ethnicity, gender, and sexuality. Women, people older than 50 years, people of Black African ethnicity, and transgender people are most likely to be diagnosed with HIV at a late stage. Women make up 30% of people living with HIV, yet they represent only 23% of participants in HIV studies. More than half of women living with HIV in the UK have experienced violence because of their HIV status, and 45% live below the poverty line.

Apea described the four As of health equity—namely, acknowledging inequality, advocating for those affected by inequalities, amplifying their needs, and acting to tackle these needs. People should not be thought of as hard to reach; instead, we should acknowledge that methods being used are not working for them. The REACH study has examined barriers to engagement in HIV care and has driven multimodal and targeted interventions to improve outcomes in the most marginalised populations. Cultural humility and listening are vital, a key part of which is ongoing community involvement and representation. Health care and research professionals have more power to enact change than do the communities they work with, and have a responsibility to advocate for their more vulnerable and minoritised patients and amplify their needs. The SHARE collaborative in east London is an example of a multimodal approach to research performed in partnership with the HIV community that aims to deliver meaningful change for the most marginalised populations. This work is not easy, and there are no shortcuts to increasing engagement with seldom heard communities. Time, resources, and a plurality of options, both online and offline, are needed.

Samantha Quaife (Wolfson Institute of Population Health) illustrated the stark influence of socioeconomic inequalities on cancer burden. Across the UK, more than 30 000 extra cases of cancer per year are attributable to socioeconomic deprivation. The all-cancer mortality rate is 53% higher in people from the most deprived backgrounds compared with the least deprived. Inequalities exist across the oncological care continuum, from screening through to end-of-life care. To improve the uptake of cancer screening, it is vital to understand modifiable determinants of behaviour. For example, people from deprived backgrounds are most likely to report intention to be screened (but non-participation), lack of awareness, lack of engagement, and a decision not to partake in screening. These individuals are also likely to not read screening invitation leaflets (eg, because of unsuitable language), so communication must be targeted accordingly. Interventions such as advance notification, tailored reminders, and simpler tests can all positively affect participation and, hence, downstream outcomes. Understanding psychological barriers to participation in cancer screening—including fatalism rooted in low confidence in treatment, little control over perceived high risk, and stigmatisation—would allow interventions to be tailored to specific populations. The study of data disaggregated by socioeconomic status, and the subsequent qualitative analysis to understand discrepancies between socioeconomic groups, has facilitated the understanding of these barriers. It will be important to use similar approaches in neurological diseases, to ensure that research translation reaches, and is relevant to, all people.

Carol Rivas (University College London, London, UK) extended the discussion by asserting that a focus on health outcomes by socioeconomic status alone leads to a unidimensional understanding of inequity. Socioeconomic differences and racial inequalities have been historically conflated, but the relation is not of simple cause and effect. Correcting for income, education, or occupational status leaves substantial ethnic disparities. The effect of individual and institutional racism on health outcomes is increasingly recognised. Many structural, contextual, and individual factors determine social disadvantage and affect health experience—but they are not additive. By using an intersectional lens to consider these factors from different perspectives, these interactions and effects can be systematically studied.

A novel way of understanding the true effect of multiple social determinants is by co-produced research. The ongoing Coronavirus Chronic Conditions and Disability Awareness study (CICADA) uses lay researchers from minority ethnic backgrounds, who themselves have chronic conditions or disabilities, to independently perform qualitative interviews in their communities. This approach brings multiple challenges, including training the lay researchers in processes, ethics and governance, interview practice, and transferable skills. Other difficulties to be overcome include participants who cannot read or write, and the need to conduct interviews across multiple dialects. However, the benefit in terms of trust, additional research understanding, and making the findings truly relevant to the most affected communities outweigh these challenges.

Andrew Singleton (National Institutes of Health, Bethesda, MD, USA) discussed the need for equity in genetic research in neurology, arguing for parity, clarity, and efficacy. With this idea, it is believed that parity of access to research will improve clarity about disease processes, leading to increased efficacy of treatments, potentially via targeted or personalised therapies. Genetic targets identified in genome-wide association studies done in one racial group (usually individuals with northern European ancestry) do not always generalise to other racial groups. For example, APOE ɛ4 alleles have discrepant risk profiles in people from different ethnic backgrounds, and polygenic risk scores translate poorly across ancestral groups.

Engaging understudied communities for genetic research is not easy. Resources are needed for infrastructure, training, and capacity building. Furthermore, funding bodies need to support projects that promote inclusivity, which can be perceived as being high risk because the work is not being performed by established groups. The Global Parkinson's Genetics Program is meeting this challenge by funding structural research priorities, including democratisation of data (eg, making local data available to local researchers), diversity in research and researchers, collaboration and cooperation, and developing meaningful infrastructure alongside research production. Expansion of work in under-represented groups in an ethical and sustainable way requires the promotion of inclusion and personal development within these groups, which in turn requires access to experts and substantial training locally—similar to the training of lay researchers.

Which should be the next steps for studies in neurological diseases? Research has, historically, been subject to considerable bias, with a failure to systematically study the effects of social and other inequalities. Although this shortcoming is not unique to neurology, the field is only just starting to recognise and address it. The neurological community has much to learn from other chronic diseases. Social inequalities affect people at all disease stages, and we need to move away from a one-size-fits-all model of research. It is vital to improve representation within research topics, participants, and researchers. Researchers must focus on what the research process gives back at all levels, in terms of training, infrastructure, and relevant findings that inform personalised interventions or policy. Doing truly inclusive research carries considerable financial and time cost, and funders should also accept the challenge to enable us to start to address the impact of social inequalities. The challenge to change might appear overwhelming but, by recognising it and tackling parts of the challenge incrementally, change can be enacted.