Deciphering an evidence base for healthy cities : residential built environment, and cardiovascular and mental health

Abstract

There has been a surge of studies suggesting that well planned and designed urban built environment could benefit population health. Scientific evidence on the links between specific built environment attributes and chronic health outcomes are of significant importance to inform future policies and design interventions for Healthy Cities. Among all health outcomes, cardiovascular diseases and mental health disorders are leading causes of death and disability. However, existing evidence have often been limited by methodological shortcomings related to study design, sample size and exposure and health outcome assessments. With an objective of overcoming these methodological bottlenecks, this thesis aims to decipher associations of residential built environments, specifically residential density, greenness and walkability with cardiovascular risks and mental health and leverages on data from Hong Kong and the UK. The first section of the thesis conceptualizes a framework of Density, Destination, Design and Salutogenicity (3DS) to study the associations of multi-scalar residential built environments with cardiovascular risks and mental health. Systematic reviews were conducted to summarize existing findings on the links between built environment and cardiovascular risks and mental health. Large-scale population health cohort data from the Hong Kong FAMILY Cohort and UK Biobank with related individual-level spatial exposure databases Hong Kong Housing Environment Database (HKHED) and UK Biobank Urban Morphometric Platform (UKBUMP) for conducting the empirical studies in the thesis has also been described. The second section comprises two empirical studies examining associations of built environments with cardiovascular risk factors. The first empirical study examined the associations of residential densities at multiple scales (within-apartment, building block and at neighbourhood level) with prevalent and incident hypertension in Hong Kong. An inverse association was evident between living space and neighbourhood residential density within 0.5 mile street catchment, and prevalent hypertension, while building density showed a positive association. The second study examined associations of walkability and greenness with arterial stiffness in the UK. The results showed significant inverse associations between walkability and greenness assessed within a 1-kilometre (Km) catchment, and arterial stiffness index. The third section comprises another two empirical studies examining associations of built environment with mental health and social well-being. The first study investigated multilevel longitudinal associations of residential densities at multiple scales with depressive sequelae in Hong Kong. Over a mean follow-up period of 2.2 years, significant inverse associations between living space and probable major depression and depressive symptoms were reported, while building density was associated with more depressive symptoms. The second study examined associations of residential density within 1- and 2-Km residential street catchments with loneliness and social isolation. Residential density was found to be associated with higher odds of loneliness and social isolation. Leveraging data from two prominent health cohorts in Hong Kong and UK, highly characterized individual-level 3DS measures of multi-scalar residential density, walkability and greenness were found to be associated with cardiovascular and mental health. As a strategy for Healthy Cities – optimizing residential built environments can act as preventive interventions for lowering the risk of chronic diseases.