Social determinants of dementia: A cross-country investigation between UK and Japan

Dementia is one of the major contributors to disability and dependency amongst the elderly population, and a significant public health issue for government and policymakers throughout the world. Recent evidence suggests that in the UK, people with dementia are at increased mortality risk compared with similarly aged people without dementia, overtaking cardiovascular disease. Even though the prevalence of dementia in the UK is rising due to higher numbers of people surviving into older ages, recent evidence suggests that the UK is experiencing a decline in dementia incidence. By contrast, Japan has witnessed a different trend, with increases in both incidence and prevalence. This difference could be related to diagnostic practice within each country, which needs to be further explored or to the cultural variability in the risk and protective factors driving these emerging forecasts that remain fundamentally different between the UK and Japan.
Research in this field has been dominated by clinical studies of dementia mostly conducted in the UK and US, and the current evidence base lacks reliable national data on incidence and prevalence of dementia that are vital for service planning, the prediction of future needs, estimating the costs of dementia care. Examining the influence of social factors on mental health is one of the ESRC's core strategic priorities.
Moreover, addressing socioeconomic inequalities and social determinants of health is a major focus for policy, so it is crucial to understand how these factors affect dementia incidence globally, and more specifically in geographical regions where the incidence trends seem to be diverging (e.g. the UK and Japan).
The overall aim is to create a collaborative network between investigators from three longitudinal studies of ageing: the English Longitudinal Study of Ageing (ELSA) in the UK, the Japan Collaborative Cohort Study (JACC study) and Japan Gerontological Evaluation Study of Aging (JAGES), which are ideally placed for conducting cross-cohort comparisons using harmonised longitudinal analyses and address the following research questions:
1. What are the social determinants of dementia in England and Japan?
2. What are the exploratory mechanisms of the divergent trends in dementia incidence observed in England and Japan?
3. What are the critical differences between the social determinants of dementia in England and Japan?
The specific objectives of this project are to lay the groundwork for future larger-scale cross-country investigations, which are essential and timely given that Japan experiences a fundamentally opposite trend in dementia incidence compared to the UK. We plan to organise a number of network events in London and Osaka, comprising of an international seminar, data harmonisation and policy workshops and offer the opportunity for the two Early Career Researchers to broaden their research horizons and exchange their work experience in renowned international teams. They will visit London and Osaka to gain in-depth insight into other data cohorts, and have opportunities to learn new cross-cohort analytical techniques, contributing to the establishment of a UK-Japan collaborative partnership in dementia. We anticipate that findings from this study will help policymakers and practitioners develop policies and interventions that can help improve health on older population and reduce dementia risk, especially in the most vulnerable groups.

This project is likely to have considerable societal and academic impact on the international scientific community. The proposed collaboration between the UK and Japan is multidisciplinary in nature, and the proposed research approach will provide great benefits to academics across several disciplines including social sciences, epidemiology, public health, psychology and neuroscience. Secondly, policymakers, as well as key workers (i.e. public health nurse and social workers), will benefit from this project findings and dissemination. Comparisons of the social determinants of dementia and the risk factors associated in each country could facilitate a better understanding of the actual differences in dementia risks. These findings could contribute to the knowledge base underpinning country-specific health policies targeting older people health, reducing socioeconomic inequalities and introducing new effective interventions to reduce dementia risk. Importantly, this international collaborative research will enrich networks between the two countries and contribute to constructing the foundation of multi-disciplinary research in this filed to exchange research, policies and practices in a broader range for a mutual benefit. This collaboration will also strengthen the newly formed partnership between University College London and Osaka University; facilitate knowledge transfer and data sharing.
From the viewpoint of the impact on the society, we have identified four distinct groups who may benefit from this international collaborative research:
1. Policy makers and advisers
Governmental departments such as the Department of Health and Social Care and Public Health England will be only some of the target organisation to influence their policy and reforms. Demands for evidence about dementia prevention is currently high in every society. Information about dementia prevention across lifespan on individual, family, workplace and community setting will influence systems for hospital care design for potential patients as well as comprehensive community care in the ever growing older societies. We anticipate these governmental departments to also have interests in international comparisons with other countries such as Japan and estimate the effects of prevention for the total population worldwide.
2. Health and welfare organisations
Expected findings will be highly relevant to charities such as AgeUK, Alzheimer's Society and Mind who will be able to provide advice to older people about the lifestyles and activities benefiting reduced risks of the dementia onset in the community in their later stage of life. Also, Local Municipality Offices, as well as the community organisation of social welfare and community work in Japan, will benefit of these findings to inform their activities for dementia prevention programs planned for their local communities. Furthermore, health professionals who work in the community will benefit from understanding the potential mechanisms and social impact of the dementia prevention.
3. Social science in the UK through the development of new and established skilled researchers in cross-disciplinary and multi-disciplinary areas. This is vital where social science as a discipline and social scientists as individuals will make ongoing contributions to evidence-based policy-making and will influence public policies and legislation at the local, regional and national levels.
4. Social Policies and programs to promote healthy ageing for all individuals in the society are highly required in this rapid ageing society. Consequently, dementia prevention will contribute worldwide to increase the years of disability-free and independent living, which affect the social cost of the medical, and health insurance expenditures. Reducing the healthcare costs and improving older people's quality of life is an international societal priority and government's agenda both in the UK and Japan.