The impact of the Environment and Pollution On Cognitive Health (EPOCH): Building the knowledge base through international collaboration

Dementia, a syndrome related to a decline in cognitive function and loss of functional ability, has been recognised to be a critical issue in ageing societies across the globe. To develop strategies for reducing the risk of cognitive decline and dementia, a large body of research has identified several lifestyle factors that maintain cognitive function and health status (e.g., physical activity and social interaction), and some chronic conditions with detrimental effects on cognitive function (e.g., hypertension and diabetes). Since the built environment - human-made infrastructures and facilities, such as street network and public transport - can play a key role in influencing health behaviours and prevention of obesity and non-communicable diseases, it is important to investigate the potential impact of the built environment on cognitive health in older people and further consider other related environmental characteristics, such as the natural environment (non-human made surroundings such as green and blue spaces) and pollution (air pollutants and noise).

Recent studies have suggested that vibrant, high-density, destination-rich neighbourhood environments can provide opportunities for older residents to engage in physical, social and mental activities that benefit cognitive health. However, such environments are also associated with harmful levels of traffic-related pollution and noise, which are found to have a negative influence on cognitive decline and dementia. It is essential to understand these complex and interacting factors in neighbourhood environments and their joint impact on cognitive health and identify key environmental factors that reduce the acceleration of cognitive decline and prevent the development of cognitive impairment and dementia. This evidence will inform multi-level, multi-sectoral prevention strategies to address challenges related to population ageing and burden of dementia through the improvement of urban planning and design, the transportation system, environmental protection practices and public health interventions.

To address these knowledge gaps, the aim of this project is to investigate the complex relationships between the built environment, natural environment and pollution and their potential impact on cognitive health in later life. Utilising interdisciplinary data resources from the health and social sciences, the project will create innovative datasets integrating environmental and individual health data in the UK and Australia. Novel analytical methods will also be developed to investigate (1) how different environmental factors in neighbourhoods can influence cognitive decline and dementia in older people; (2) how lifestyle behaviours (levels of engagement in physical, social and mental activities) can explain the impact of neighbourhood environments on cognitive health; (3) whether the effects of neighbourhood environments depend on sex, socioeconomic status and genetic predisposition to dementia. Similar research methods and analytical approaches will be carried out in different populations across the UK and Australia to provide comparable results for cross-country comparison. The international collaboration will maximise the potential for developing the next generation of researchers in the environment, cognition and ageing research fields and create a cross-disciplinary network for future research and innovations. The outputs of this project will contribute to knowledge and methodologies that will advance research on environment, cognition and ageing and enhance evidence-based strategies to reduce the risk of accelerated decline in cognitive function and prevent the progression toward cognitive impairment and dementia.

Vibrant, high-density, destination-rich neighbourhood environments provide opportunities for older residents to engage in physical, social and mental activities that benefit cognitive health. However, such environments are also associated with harmful levels of air pollution and noise, which can have a negative impact on cognitive decline and dementia. The aim of this project is to investigate the joint impact of multiple neighbourhood environmental attributes on cognitive health in later life using interdisciplinary data resources in the UK and Australia. This project will integrate data on the neighbourhood built environment (dwelling density, street intersection density, land use, public transport and different types of services), natural environment (greenness, distance to parks and natural aquatic features), pollution (air pollutants and noise) and population-based cohort studies (UK: Cognitive Function and Ageing Study (CFAS) II, CFAS Wales, English Longitudinal Study of Ageing (ELSA); Australia: Personality And Total Health through life project (PATH), Sydney Memory and Ageing Study (MAS), Older Australian Twin Study (OATS)) and develop novel analytical frameworks using the integrated datasets and a study with existing environmental measures (UK Biobank). Advanced statistical methods such as generalised structural equation modelling, nonlinear structural equation mixture modelling and multistate modelling will be used to examine hypotheses on the relationships between different neighbourhood environmental attributes and cognitive health measures and investigate the meditating effects of lifestyle behaviours (engagement in physical, social and mental activities) and the modifying effects of sociodemographic (sex, socioeconomic status) and genetic risk factors (APOE genotype). Bayesian evidence synthesis approaches will be employed to integrate results from individual cohorts within UK and Australia and provide pooled estimates for cross-country comparison.

The outputs of this project will have a strong impact on the research community, policy makers, civic organisations and the pubic and inform evidence-based strategies for risk reduction of cognitive decline and dementia via improving neighbourhood environments and creating a supportive environment for the growing numbers of older people across the world.

(1) Impact on knowledge and research: This interdisciplinary project will make substantial theoretical and methodological contributions to environmental, cognitive and ageing research. The findings will inform how and for whom the joint effects of a comprehensive set of interrelated environmental factors are beneficial and harmful to cognitive health. This will address limitations of prior research focusing on single dimensions of the neighbourhood environment (harmful pollutants or activity-supportive aspects of the built environment) and contribute to the development and refinement of a comprehensive theoretical model of environmental influences on cognitive health in later life. This collaborative project will bring together resources and expertise from the UK and Australian research teams and carry out similar analyses across cohort studies to allow cross-country comparison. The evidence generated from this project will guide the conceptualisation and design of future observational and intervention studies.

(2) Impact on policy and practice: The findings of this project will identify key environmental factors, particularly in the built environment, related to cognitive health in later life and provide robust evidence to inform public health, urban planning, transportation and environmental protection policies and practices. The project will identify how neighbourhood environments can support cognitive health in older people, what are favourable or unfavourable environmental characteristics, and who are vulnerable groups that are most affected by unfavourable neighbourhood environments or individual characteristics. These findings will address the United Nation's Sustainable Development Goal 11: 'to make cities and human developments inclusive, safe, resilient and sustainable by 2030', which highlights the importance of creating a supportive environment for population health through improving road safety, public transport, air quality and access to green and public spaces. This project will provide specific information on the links between the environment and cognitive health in later life and generate robust evidence informing recommendations on optimal levels of environmental attributes, such as the maximal distance to green spaces from residential areas, the minimal level of access to public transport, or the 'safe' concentration levels of traffic-related pollution for cognitive health in the two nations. This will inspire the commitment and collaboration across the public health, urban planning, transportation and environmental protection sectors to incorporate environmental factors into prevention strategies for cognitive decline and dementia and develop specific guidelines to improve neighbourhood environments in different areas.

(3) Impact on civic organisations and the public: The outputs of this project will benefit civic organisations focusing on the promotion of healthy ageing and on the creation of age-friendly, sustainable and healthy communities. Civic organisations will be able to use the project findings to identify issues in local areas and inform policy gaps in the health and social care, transportation or urban planning sectors and, subsequently, reframe policy debates and engage stakeholders to improve understanding of the key environmental issues and devise actionable solutions. The improvement of neighbourhood environments and changes in relevant policies will ultimately benefit the public and reduce the risk of cognitive decline and dementia in older populations.