The Role of The Residential Environment on Biological Ageing in the UK

As life expectancy increases, the burden of disease and disability continues to escalate in ageing societies, necessitating a proactive approach to identifying disease risk. While chronological age conventionally serves as the yardstick for measuring ageing, it fails to encapsulate the intricate and diverse trajectories of age-related decline experienced by individuals across various organ systems. Biological ageing thus gained prominence as a more nuanced marker for disease risk and mortality. Current research on ageing predominantly focuses on the elderly population, neglecting that age-related changes to physiological processes may commence in early adulthood. The WHO Social Determinants of Health framework shows that structural inequalities will influence health through intermediary determinants, including material, behavioural, and psychosocial factors. People's socioeconomic position (SEP) can indicate structural inequalities, which influence the ageing process. Wealth as a crucial measure of SEP is particularly salient to older people as it captures the life-course accumulation of assets, and one of the different measures of SEP, area levels of deprivation, may be more suitable for whole-adulthood people. Limited attention has been given to residential environments and multiple organ systems ageing measurements, but less to the entire age range of adults. Exposures to poor living environments may increase people's stress levels, and biological changes may occur if the body is exposed to chronic stress, resulting in dysregulation of the multiple bodily systems, which may increase biological ageing speed. Identifying the biological ageing process and its social determinants throughout the entire adult lifespan can delay or avoid the onset of age-related diseases and substantially enhance health outcomes in later life.

This study aims to assess the association between the residential environment and adults' biological ageing process using data from Understanding Society. Firstly, this study will compare the multiple organ systems ageing measurements for adults with different socio-demographic characteristics, and then use Pearson and Spearman correlations to see their association with physical and cognitive functioning measures, as well as use latent growth curve modelling to track how the measures of biological ageing are associated with a subsequent decline in health-related quality of life. Secondly, this study will examine the association between area-level SEP measurements and multiple organ systems ageing measurements using two-level random-intercept regression models. Thirdly, this study will explore whether individual physical housing environments have potential mediating effects and to what extent the individual housing environment mediates associations between area deprivation and biological ageing using structural equation modelling.

In this study, area deprivation indexes can be seen as multidimensional area-level structural determinants through material mediation pathways (individual physical housing environments) influencing biological ageing for all age-span adults in the UK. This study can help identify residential inequalities in resources across small geographic areas, which has significant implications for breaking the cycles of poverty and reducing the cost and resources required for ageing and disease-related interventions to minimize health inequalities.