Chinmoy Sarkar

Built environment configuration and change in body mass index: the Caerphilly Prospective Study (CaPS).

There exist no long term longitudinal studies assessing BMI trends of older adults in relation to the built environment. We employed cohort data from the Caerphilly Prospective Study (CaPS) to analyze the long term independent associations between a broad set of built environmental factors and change in BMI measured at three time points over a 12-year period. Built environment morphological metrics (morphometrics) used include measures of land use accessibility and space syntax modelled street network accessibility. A multilevel modelling framework was adopted wherein measurement occasions were nested within individuals and individuals were nested within LSOA census areas. BMI was observed to be significantly (p<0.05) associated with a number of built environment factors including mix; density of retail, churches, recreational and leisure services; street network accessibility as well as slope variability. Controlling for socio-demographic and lifestyle factors and for vascular diseases had negligible impact upon the influence of built environmental factors highlighting the importance of urban design and planning in community public health interventions.

Urban built environment configuration and psychological distress in older men: Results from the Caerphilly study

BackgroundFew studies have examined the impact of the built environment configuration upon mental health. The study examines the impact of objectively assessed land use and street network configuration upon psychological distress and whether this association is moderated by the natural environment and area-level deprivation.MethodsIn a community sample of 687 older men from the Caerphilly Prospective Study, built environment morphological metrics (morphometrics) were related to differences in psychological distress as measured by the General Health Questionnaire. Cross-sectional data were taken from the most recent (5th) phase. A multi-level analysis with individuals nested within census-defined neighbourhoods was conducted. Environmental measures comprised GIS-constructed land use and street network metrics, slope variability and a satellite derived measure of greenness.ResultsReduced psychological distress was associated with residing in a terraced dwelling (OR = 0.48, p = 0.03), higher degrees of land-use mix (OR = 0.42, p = 0.03 for the high tertile) and having higher local-level street-network accessibility (‘movement potential’) (OR = 0.54, p = 0.03). Hillier topography with higher slope variability was associated with increased risks of psychological distress (OR = 1.38, p = 0.05).ConclusionsThe findings support our hypothesis that built environment configuration is independently associated with psychological distress. The study underscores the need for effective intervention in the planning and design of residential built environment to achieve the goal of health-sustaining communities.

UK Biobank Urban Morphometric Platform (UKBUMP) – a nationwide resource for evidence-based healthy city planning and public health interventions

The built environment (BE) has emerged as one of the ‘first causes’ of chronic disease, capable of explaining its socio-spatial variation. There is an increasing need for objective, detailed and precise measurements of attributes of BE that may influence our lifestyle, behaviour and hence physical and mental health. In this paper, we report the UK Biobank Urban Morphometric Platform (UKBUMP), the first ever very large sample size high resolution spatial database of urban morphological metrics (morphometrics), being developed for half-a-million participants of the UK Biobank Prospective study spatially distributed across 22 UK cities. Large-scale objective assessment of the BE was conducted employing state-of-the-art spatial and network analyses upon multiple national-level spatial data-sets. Prospective large-scale objective assessment of the BE enables the development of BE-health modelling studies that have the potential to identify causal pathways from specific attributes of the BE to various complex chronic health outcomes as well as well-being. The UKBUMP will act as a national resource, providing a platform for evidence-based healthy city planning and interventions for the first half of the twenty-first century.

Association between adiposity outcomes and residential density: a full-data, cross-sectional analysis of 419 562 UK Biobank adult participants

BACKGROUND Obesity is a major health issue and an important public health target for urban design. However, the evidence for identifying the optimum residential density in relation to obesity has been far from compelling. We examined the association of obesity with residential density in a large and diverse population sample drawn from the UK Biobank to identify healthy-weight-sustaining density environments. METHODS For this full-data, cross-sectional analysis, we used UK Biobank data for adult men and women aged 37-73 years from 22 cities across the UK. Baseline examinations were done between 2006 and 2010. Residential unit density was objectively assessed within a 1 km street catchment of a participants residence. Other activity-influencing built environment factors were measured in terms of density of retail, public transport, and street-level movement density, which were modelled from network analyses of through movement of street links within the defined catchment. We regressed adiposity indicators of body-mass index (BMI; kg/m2), waist circumference (cm), whole body fat (kg), and obesity (WHO criteria of BMI ≥30 kg/m2) on residential density (units per km2), adjusting for activity-influencing built environment factors and individual covariates. We also investigated effect modification by age, sex, employment status, and physical activity. We used a series of linear continuous and logistic regression models and non-linear restricted cubic spline models as appropriate. FINDINGS Of 502 649 adults in the prospective cohort, 419 562 (83·5%) participants across 22 UK Biobank assessment centres met baseline data requirements and were included in the analytic sample. The fitted restricted cubic spline adiposity-residential density dose-response curve identified a turning point at a residential density of 1800 residential units per km2. Below a residential density of 1800 units per km2, an increment of 1000 units per km2 was positively related with adiposity, being associated with higher BMI (β 0·19 kg/m2, 95% CI 0·14 to 0·24), waist circumference (β 0·41 cm, 0·28 to 0·54), and whole body fat (β 0·40 kg, 0·30 to 0·50), and with increased odds of obesity (odds ratio [OR] 1·10, 1·07 to 1·14). Beyond 1800 units per km2, residential density had a protective effect on adiposity and was associated with lower BMI (β -0·22 kg/m2, -0·25 to -0·20), waist circumference (β -0·54 cm, -0·61 to -0·48), and whole body fat (β -0·38 kg, -0·43 to -0·33), and with decreased odds of obesity (OR 0·91, 0·90 to 0·93). Subgroup analyses identified more pronounced protective effects of residential density among individuals who were younger, female, in employment, and accumulating higher levels of physical activity, except in the case of whole body fat, for which the protective effects were stronger in men. INTERPRETATION Housing-level policy related to the optimisation of healthy density in cities might be a potential upstream-level public health intervention towards the minimisation and offsetting of obesity; however, further research based on accumulated prospective data is necessary for evidencing specific pathways. The findings might mean that governments, such as the UK Government, who are attempting to prevent suburban densification by, for example, prohibiting the subdivision of single lot housing and the conversion of domestic gardens to housing lots, will potentially have the effect of inhibiting the conversion of suburbs into more healthy places to live. FUNDING University of Hong Kong, UK Biobank, and UK Economic & Social Research Council.

Residential greenness and prevalence of major depressive disorders: a cross-sectional, observational, associational study of 94 879 adult UK Biobank participants

BACKGROUND Increased urbanisation and the associated reduced contact of individuals with natural environments have led to a rise in mental disorders, including depression. Residential greenness, a fundamental component of urban design, has been shown to reduce the public health burden of mental disorders. The present study investigates the association between residential green exposure and prevalence of major depressive disorders using a large and diverse cross-sectional dataset from the UK Biobank. METHODS In this cross-sectional, observational, associational study, we used baseline data from the UK Biobank cohort of participants aged 37-73 years from across the UK. Environmental exposure data were derived from a modelled and linked built environment database. Residential greenness was assessed with a 0·5 m resolution Normalised Difference Vegetation Index, which is derived from spectral reflectance measurements in remotely sensed colour infrared data and measured within geocoded dwelling catchments. Other environment metrics included street-level movement density, terrain, and fine particulate exposures. A series of logistic models examined associations between residential greenness and odds of major depressive disorder after adjusting for activity-influencing environments and individual covariates. FINDINGS Of 122 993 participants with data on major depressive disorder, the study analytical sample comprised 94 879 (77·1%) participants recruited across ten UK Biobank assessment centres between April 29, 2009, and Oct 1, 2010. A protective effect of greenness on depression was consistently observed, with 4·0% lower odds of major depressive disorder per interquartile increment in Normalised Difference Vegetation Index greenness (odds ratio 0·960, 95% CI 0·93-0·99; p=0·0044). Interaction analyses indicated that the beneficial effects of greenness were more pronounced among women, participants younger than 60 years, and participants residing in areas with low neighbourhood socioeconomic status or high urbanicity. INTERPRETATION The results point to the benefits of well designed green environments on mental health. Further longitudinal studies are needed to decipher causal pathways. In the UK, policies aimed at optimising allocation and design of green spaces might help preserve psychological ecosystem services, thereby, improving the mental wellbeing of populations and enhancing the mental capital of cities. FUNDING University of Hong Kong, UK Biobank, and the UK Economic & Social Research Council.

The effect of street-level greenery on walking behavior: Evidence from Hong Kong

Accumulating evidence shows that urban greenspaces have great health benefits, but establishing a causal relationship is difficult. It is often hypothesized that walking and physical activity are mediators in the relationship between urban greenspaces and health outcomes. Furthermore, most urban greenspace-physical activity studies have focused on parks rather than on landscaped streets, even though the latter are the most popular places for physical activity. The lack of research attention for landscaped streets is largely due to the fact that street greenery is difficult to measure, especially at eye level. Using readily available Google Street View images, we developed methods and tools to assess the availability of eye-level street greenery. A two-layered study was developed that 1) examined the association between urban greenspaces and the odds of walking (versus not walking) for 90,445 participants in the Hong Kong Travel Characteristics Survey and 2) carried out sensitivity analysis of the association between urban greenspaces and total walking time for a subset of 6770 participants. Multilevel regression models were developed to reveal the associations between street greenery and walking behaviors while controlling for sociodemographic characteristics and other activity-influencing built environment factors, taking into account the inherent clustering within the data. The results showed that both street greenery and the number of parks were associated with higher odds of walking; street greenery but not parks was associated with total walking time. Our results suggest that walking behavior is at least as strongly affected by eye-level street greenery as by parks. They also implicitly support the health benefits of urban greenspaces via walking and physical activity. With the large sample size, our findings pertain to the entire population of Hong Kong. Furthermore, the use of Google Street View is a sound and effective way to assess eye-level greenery, which may benefit further health studies.

Neighbourhood walkability and incidence of hypertension: Findings from the study of 429,334 UK Biobank participants

BACKGROUND With an estimated one billion hypertension cases worldwide, the role of the built environment in its prevention and control is still uncertain. The present study aims to examine the associations between neighbourhood walkability and hypertension in a large and diverse population-based cohort. MATERIALS AND METHODS We examined the association between neighbourhood walkability and blood pressure outcomes for N = 429,334 participants drawn from the UK Biobank and aged 38-73 years. Neighbourhood walkability was objectively modelled from detailed building footprint-level data within multi-scale functional neighbourhoods (1.0-, 1.5- and 2.0-kilometer street catchments of geocoded dwelling). A series of linear and modified Poisson regression models were employed to examine the association between walkability and outcomes of diastolic blood pressure (DBP in mmHg), systolic blood pressure (SBP in mmHg) and prevalent hypertension adjusting for socio-demographic, lifestyle and related physical environmental covariates. We also examined the relationship between walkability and change in blood pressure for a sub-sample of participants with follow-up data and tested for interaction effects of age, sex, employment status, neighbourhood SES, residential density and green exposure. RESULTS Neighbourhood walkability within one-kilometer street catchment was beneficially associated with all the three blood pressure outcomes, independent of all other factors. Each interquartile increment in walkability was associated with the lower blood pressure outcomes of DBP (β = -0.358, 95% CI: -0.42, -0.29 mmHg), SBP (β = -0.833, 95% CI: -0.95, -0.72 mmHg) as well as reduced hypertension risk (RR = 0.970, 95% CI: 0.96, 0.98). The results remained consistent across spatial and temporal scales and were sensitive to sub-groups, with pronounced protective effects among female participants, those aged between 50 and 60 years, in employment, residing in deprived, high density and greener areas. CONCLUSION This large population-based cohort found evidence of protective association between neighbourhood walkability and blood pressure outcomes. Given the enduring public health impact of community design on individual behaviour and lifestyle, of particular interest, are the targetted upstream-level interventions in city design aimed at optimizing walkability. Further long term studies are required to assess its sustained effects upon hypertension prevention and control.

Exploring the Impacts of Housing Condition on Migrants’ Mental Health in Nanxiang, Shanghai: A Structural Equation Modelling Approach

Although rapid urbanization and associated rural-to-urban migration has brought in enormous economic benefits in Chinese cities, one of the negative externalities include adverse effects upon the migrant workers’ mental health. The links between housing conditions and mental health are well-established in healthy city and community planning scholarship. Nonetheless, there has thusfar been no Chinese study deciphering the links between housing conditions and mental health accounting for macro-level community environments, and no study has previously examined the nature of the relationships in locals and migrants. To overcome this research gap, we hypothesized that housing conditions may have a direct and indirect effects upon mental which may be mediated by neighbourhood satisfaction. We tested this hypothesis with the help of a household survey of 368 adult participants in Nanxiang Town, Shanghai, employing a structural equation modeling approach. Our results point to the differential pathways via which housing conditions effect mental health in locals and migrants. For locals, housing conditions have direct effects on mental health, while as for migrants, housing conditions have indirect effects on mental health, mediated via neighborhood satisfaction. Our findings have significant policy implications on building an inclusive and harmonious society. Upstream-level community interventions in the form of sustainable planning and designing of migrant neighborhoods can promote sense of community, social capital and support, thereby improving mental health and overall mental capital of Chinese cities.

Commuting Mode Choice in a High-Density City: Do Land-Use Density and Diversity Matter in Hong Kong?

Hong Kong is a densely populated and transit-oriented Chinese city, which provides an ideal urban environment with which to study the various successful facets of land use policy as a model for potential replication to curb increasing car use in other Chinese cities. We examine the commuting mode choice of 203,900 households living in 4768 street blocks in Hong Kong from 2011 census. A street block is the smallest planning unit, made up of one or more housing estates with a homogenous built environment and socioeconomic status. The built environment is measured using the five Ds framework, an international dimensioning framework for classifying and measuring attributes of the built environment for physical activity and travel behaviors. Generalized, multi-level mixed models were applied to detect the associations between travel choice and built environment characteristics, while adjusting for socioeconomic status. Design and destination accessibility had greater effects on the choices to walk and take public transport than on the choice to drive. Density and diversity had only marginal effects on mode choice. Unexpectedly, distance to the urban center had the opposite effect on automobile use to that found in Western studies. Hong Kong residents living close to the urban center were more likely to drive for commuting trips. The contrasting findings between our study and Western studies suggest that the associations between a high-density built environment and travel choice vary with urban context.

Toward a Metagenomic Understanding on the Bacterial Composition and Resistome in Hong Kong Banknotes

Currency is possibly one of the main media transmitting pathogens and drug resistance due to its wide circulation in daily life. In this study, we made a comprehensive characterization of the bacterial community present on banknotes collected from different geographical regions of Hong Kong (HK) by performing in vitro characterization of the bacterial presence and resistome profile, as well as metagenomic analysis including microbial diversity, the prevalence of potential pathogens, the dissemination potential of antibiotic-resistance genes (ARGs), among others. When comparing the bacterial community of HK banknotes with other HK environmental samples, including water and marine sediment, we revealed that HK banknotes cover nearly 50% of total genera found in all the environmental samples, implying that banknotes harbor diverse bacteria originated from a variety of environments. Furthermore, the banknotes have higher abundance of potential pathogenic species (~5 times more) and ARGs (~5 times more) with higher dissemination potential (~48 times more) compared with other environmental samples. These findings unveiled the capabilities of this common medium of exchange to accommodate various bacteria, and transmit pathogens and antibiotic resistance. Furthermore, the observed independence of microbiome profile from the citys topological indices led us to formulate a hypothesis that due to their high circulation banknotes may harbor a homogenized microbiome.