Lifestyle Factors in Dementia and Cognitive Impairment in England and China: The Role of Sleep and Physical Activity

Dementia is a very serious health problem affecting nearly 1 million older people in the UK, and many more millions in China. It has a huge impact on society and on the families of victims, with vast economic costs. Less severe cognitive impairment affects even larger numbers of older people, and has enormous effects on quality of life and independence. Unfortunately, medical research has yet to discover effective treatments, and this highlights the importance of prevention. Genetic and biological factors contribute to these problems, but understanding the role of social and lifestyle factors is crucial.

There are many approaches to research on dementia and cognitive impairment, but one method that is particularly valuable is the analysis of large, nationally representative, multidisciplinary longitudinal population studies. These studies have repeated waves of data collection, so that long-term associations between factors such as socioeconomic inequality or health behaviour and future cognitive impairment and dementia can be explored. Two major studies of this type are the English Longitudinal Study of Ageing (ELSA) and the China Health and Retirement Longitudinal Study (CHARLS). These studies have developed in parallel with strong harmonisation of measures. Both have cognitive data stretching back over several waves, and both have recently implemented the Harmonized Cognitive Aging Protocol (HCAP); this is a US-funded initiative, and involves a set of assessments designed to measure cognitive function in detail.

This application has emerged through a partnership between the Principal Investigators of ELSA (Andrew Steptoe) and CHARLS (Yaohui Zhao), supported by multidisciplinary collaborators. The comparison is valuable because England and China differ in many ways as regards potential risk factors, including socioeconomic inequalities, educational levels, social and cultural factors, and in the prevalence cardiometabolic risks. This Joint Call therefore provides the opportunity to discover whether the impact of risk processes is moderated by the social and cultural context. The work could lead to novel preventive strategies, and to more precise targeting of existing programmes.

The primary aim is to compare factors related to dementia and cognitive impairment in England and China. We will find out whether there are differences in the relationships between lifestyle, socioeconomic and physical health factors, and cognitive function in the two countries. We will evaluate the relevance of socioeconomic inequalities, education, family structure, social environments, lifestyle factors, and history of cardiometabolic disease and the presence of multiple illnesses to dementia risk. We will also assess changes in economic and social circumstances after a dementia diagnosis in the family. In addition, we plan to focus specifically on sleep disturbance and physical activity. The reason is that both are potentially important and both can be modified, but patterns of sleep and activity differ markedly in the two countries. One problem with analysing these issues is that self-report measures of sleep and activity are not very good, particularly among older people. Recollection can be inaccurate, napping is difficult to remember, and physical activity about the house is difficult to quantify. We will add objective measures based on wrist-worn devices to both studies during their next phases of data collection. We will then be able to discover whether there are differences between countries in the relationships of cognitive function and objectively-assessed sleep and physical activity.

We expect that our results will inform public policy and prevention strategies in the two countries. The research partnership will provide a foundation for future collaborations. We will also involve early career researchers so as to help train scientists familiar with integrating social and health research and cross-national studies

There are a number of non-academic groups who will benefit from this research:

1). Health care professionals. This research is not only of purely academic interest, but is of direct relevance to health care professionals involved with treating people with severe cognitive impairment. The scope for active medical treatments is unfortunately very limited at present, but changes in lifestyle are feasible. Our results will provide high quality evidence about the scope for supporting people with cognitive impairment in both countries, with advice and programmes that might both improve the quality of life of patients and their relatives, and potentially slow the progression of cognitive decline with age.

2). Policy makers in social and health care. There are concerns in both the UK and China in how best to manage the current and future projected levels of dementia and severe cognitive impairment. Costs could potentially be very large, so a better understanding of relevant social and lifestyle factors is essential. Policy making is carried out at the national level, but also at the local authority (UK) or county (China) levels, where the problems of limits on welfare expenditure are very striking. The evidence provided by this programme may highlight differences in relationships between cognitive function and economic and social circumstances in the two countries that will prove valuable for both. We also hope that our research partnership will give greater weight to the attention that will be paid to the findings. UCL is one of the top 15 Universities in the world according to the international QS and Shanghai Academic Rankings, while Peking University was recently identified as one of the top 'rising star' Universities for science in Nature (2019). The impact of collaborative research findings coming from this prestigious partnership is therefore likely to be substantial

3). Prevention Practitioners. The dearth of medical treatments indicates that prevention is key to managing the dementia crisis in both countries. This research will highlight important lifestyle factors that are relevant to the development of dementia and cognitive impairment, and whether these vary between the UK and China. In particular, we anticipate that the new findings on sleep will provide fresh avenues in prevention that can be exploited by practitioners in this field.

4). NGOs, voluntary sector and local community groups. Voluntary organisations and third sector groups play a vital role in informing the public, and in supporting people with cognitive impairment. In China, there is increasing involvement of volunteers in community-based NGOs supporting people with dementia and family carers, while in England there is involvement both at the national level with organisations such as Age UK and the Alzheimer's Society, and activities at the local level by small formal and informal groups. Organisations such as HelpAge International are supporting innovative programmes in both countries. The insights our research will provide into the importance of sleep and physical activity patterns and social processes will be valuable in both countries.

We will disseminate findings through non-academic social media outlets (website and blogging platforms in both countries), targeted briefings and workshops. The exact content and location will emerge through local discussions with older people and relevant organisations in the two countries.