Title: Lifestyle Factors in Dementia and Cognitive Impairment in England and China: The Role of Sleep and Physical Activity
Funder: Medical Research Council

Abstract: 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 scient


Research activity codes: 2.3 PSYCHOLOGICAL, SOCIAL AND ECONOMIC FACTORS
Health categories: NEUROLOGICAL;MENTAL HEALTH