Bulletin January 2018 (Vol. 19 No. 2)

The associations between walkability, greenness and density and public health have been demonstrated in studies by HKU and Oxford academics that use big data to provide the evidence. CITIES THAT MAKE YOU WANT TO GET ACTIVE Dr Chinmoy Sarkar in the Faculty of Architecture’s Healthy High Density Cities Lab, HKUrbanLab, works at the interface of two disciplines, urban planning and medicine, a unique combination that he believes has the potential to improve public health. “We have growing pressures in cities with ageing populations and spiralling health expenditures from chronic disease. If we can make small tweaks and retrofits to the built environment design, we can produce small but nonetheless significant effects on our health. In a city of millions, that can save billions of dollars incurred in health expenditure,” he said. With the aim of designing active-living environments, he has used big data to show how the built environment has direct impacts on physical activity and on people’s health more generally. In studies he conducted with Professor Chris Webster, HKU’s Dean of Architecture, 10 per cent higher odds of obesity and 14 per cent higher odds of reporting low physical activity. If they lived in neighbourhoods with densities of 1,800 units or higher, they had nine per cent lower odds of obesity and five per cent lower odds of reporting low physical activity. Professor John Gallacher of Oxford’s Department of Psychiatry and Honorary Professor of Architecture at HKU, and other scholars, Dr Sarkar has provided evidence of impacts in the UK, and is now preparing to do the same in Hong Kong and Mainland China. For the UK studies, the researchers drew from a huge biobank of half a million people in 22 cities to develop a detailed database, the UK Biobank Urban Morphometric Platform, comprising health-influencing built environment metrics of density, street layouts, salutogenic greenery, amenities such as fast food outlets and sports facilities, measured in relation to where the people reside. Links with weight outcomes and physical activity In one study, Dr Sarkar and his colleagues compared urban density with weight outcomes. They found that at densities below about 1,800 units per square kilometre, people had “There has been some resistance to suburban densification in the UK, so this study shows that it can be a public health opportunity to be embraced, especially by creating active and multifunctional spaces,” he said. Greenness also matters. Using high-resolution photos of neighbourhoods taken from the sky, the researcher showed that increased greenness within 500 metres of one’s home was associated with 3.2 per cent lower odds of obesity and four per cent higher odds of reporting more than 30 minutes of walking. Another study of 15,000 people in London and involving the London Travel Demand Survey, found the density of trees and street-level accessibility were associated with higher odds of walking. Another five-year study of London found street accessibility and morphology to have a significant effect on the odds of being killed or severely injured in a traffic accident. And yet another, soon-to-be-published study has found a link between the walkability of the built environment and blood pressure. “If we did these studies on 500 people and tried to infer an association, it would be very difficult to influence planners, policy-makers and politicians. But detailed country-wide studies are more reliable and generalisable. Hopefully they will look at the science and be convinced,” Dr Sarkar said. Optimising the environment for health The UK is not the only focus. Hong Kong has The FAMILY Cohort, a territory-wide study to understand the health, happiness and harmony at individual, household and neighbourhood levels, of 46,000 participants and the HKU’s Architecture and Medical Faculties are collaborating on a series of studies to decipher evidence here. In addition, Oxford University has a biobank of half a million people in 10 Chinese cities. Professor Webster, Dr Sarkar and colleagues plan to discern associations between the built environment and health in fast-urbanising Chinese cities. Each place is expected to have its own issues – in the UK and North American cities, greater density may be a boon to public health while in crowded Asian cities like Hong Kong, a different outcome may prevail. The point at this stage is to gather to see what the associations are between exposure, behaviour and health in large-scale health cohorts around the world. Dr Sarkar hopes that ultimately the findings will encourage planners to design and configure cities that are health-promoting and encourage people to walk throughout their lives so they can reap the health benefits. He also hopes planners will think in terms of reducing exposure to negative externalities, such as traffic pollution, and regard features such as parks as more than recreational add-ons. “The effects of design interventions may seem small, nonetheless, active environments also encourage more social interactions – the effects are significant and pervasive. If we can design environments that encourage healthier behaviour and lifestyles, it would contribute to reducing our growing burden of chronic disease and health expenditures and enhance mental capital,” he said. “That’s our goal: optimise the built environment, minimise negative exposures and develop predictive models of urban scenarios and population health outcomes.” █ Network modelled street-level movement density (betweenness) at spatial scales of 400m and 3,000m for Greater London. Healthy Cities: Public Health through Urban Planning is co-authored by Dr Chinmoy Sarkar and Professor Chris Webster, HKU’s Faculty of Architecture, and Professor John Gallacher, Department of Psychiatry, Medical Sciences Division, University of Oxford. Dr Sarkar and his team compared urban density with weight outcomes. The study shows that at densities below about 1,800 units per square kilometre, people had 10 per cent higher odds of obesity. If they lived in neighbourhoods with densities of 1,800 units or higher, they had nine per cent lower odds of obesity. If we did these studies on 500 people and tried to infer an association, it would be very difficult to influence planners, policy- makers and politicians. But detailed country-wide studies are more reliable and generalisable. Hopefully they will look at the science and be convinced. Dr Chinmoy Sarkar 05 | 06 The University of Hong Kong Bulletin | January 2018 Cover Story