*adapted from the contents published by the Li Ka Shing Faculty of Medicine, The University of Hong Kong at http://www.med.hku.hk/v1/archives/13748

Professor Ester Cerin, Visiting Professor of the School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong (HKU) co-authored an international study which finds that people who live in activity-friendly neighbourhoods take up to 90 minutes more exercise per week. The study (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)01284-2/fulltext) has important implications for public health policy and practice and has been published in the prestigious The Lancet on April 2, 2016.

Research method

The international study aims to investigate the amount of physical activity in relation to urban environments. It included 6,822 adults aged 18-66 from 14 cities in 10 countries from the International Physical Activity and Environment Network (IPEN). The cities or regions included were Hong Kong (China), Ghent (Belgium), Curitiba (Brazil), Bogota (Colombia), Olomouc (Czech Republic), Aarhus (Denmark), Cuernavaca (Mexico), North Shore, Waitakere, Wellington and Christchurch (New Zealand), Stoke-on-Trent (UK), Seattle and Baltimore (USA).

The research team mapped out the neighbourhood features from the areas around the participants’ homes, such as residential density, number of street intersections, public transport stops and parks, the nearest public transport points, and mixed land use. Physical activity was measured by using accelerometers worn around participants’ waists for a minimum of four days, recording movement every minute.

Important contribution from Hong Kong to the international study and its major findings

“Hong Kong is a unique and diverse community and played a very important role in this international study,” says Professor Cerin, co-author of the study and Visiting Professor of School of Public Health, Li Ka Shing Faculty of Medicine, HKU. “It greatly expanded the range of variability in the neighbourhood features of interest to us. Many Western cities have relatively low residential density and poor access to public transport and services. In contrast, Hong Kong’s neighbourhoods are very diverse – some have relatively low density (e.g. Lantau Island) while others (e.g. Mong Kok) are among the most densely populated neighbourhoods in the world. Hong Kong is an exciting place to study and contributes critical information relevant to global urban planning policies and practice,” said Professor Cerin.

“The average amount of physical activity in Hong Kong was 44 minutes per day of moderate to vigorous physical activity, most of which were accumulated through walking for transportation,” adds Professor Cerin. “Other analyses we have done and reported in another paper showed that high residential density and easy access to services and public transport are not the only features that help Hong Kong adults be more active than residents of other IPEN cities,” Professor Cerin explained. “Safety from crime is another important factor. Hong Kong is safer than most other IPEN cities. People are not afraid to walk on the streets at any time of the day and night. Hong Kong also has relatively good pedestrian infrastructure and safety that promote walking. Another characteristic of Hong Kong residents that help them be more active is not having a car. From a population health and environmental sustainability viewpoint, this is a great thing for a city to be known for,” said Professor Cerin.

The study also found that on average, participants across all 14 cities did 37 minutes moderate to vigorous physical activity per day – equivalent to brisk walking or more. The four neighbourhood features which were most strongly associated with increased physical activity were high residential density, large number of intersections and public transport stops, and more parks within walking distance. The difference in physical activity between participants living in the most and least activity-friendly neighbourhoods ranged from 68-89 minutes per week, representing 45-60% of the recommended 150 minutes per week.

Relationship between the urban environment and physical activity

Professor James Sallis, lead author of the study from the University of California, San Diego, USA, further explains, “Neighbourhoods with high residential density tend to have connected streets, shops and services, meaning people will be more likely to walk to their local shops. Interestingly, distance to nearest transport stop was not associated with higher levels of physical activity, whereas the number of nearby transport stops was. This might mean that with more options, people are more likely to walk further to a transport stop that best meets their needs. The number of local parks was also important since parks not only provide places for sport, but also a pleasant environment to walk in.”

Writing in a linked Comment, Dr Shifalika Goenka, Public Health Foundation of India, Delhi, India, estimates, “The total health gained by changing to optimal activity friendly environments will be close to 2 million fewer deaths and around 3% fewer non-communicable diseases.” Dr Goenka says that the article presents clear evidence for the role of the urban built environment in enhancing physical activity levels of entire populations.

The Healthy City Initiative

With physical inactivity responsible for over 5 million deaths per year, the authors say that creating healthier cities is an important part of the public health response to the global disease burden of physical inactivity.

The School of Public Health of Li Ka Shing Faculty of Medicine, HKU has been working with colleagues locally and internationally to study the effect of the built environment and urban design on health, and its implications for public health policy and practice. In collaboration with HKU Faculty of Architecture, the team of researchers at School of Public Health are conducting multi-disciplinary studies on the healthy city initiative, which aims to provide evidence-based research to help inform public health policy of both local and global relevance. “One of our interdisciplinary groups has been studying the effects of the neighbourhood environment on the physical activity of Hong Kong residents across the whole life span, from pre-schoolers to older adults, for over a decade. These studies are making an important contribution to the local and global health agenda and knowledge base and we now need the cooperation of policy makers and professionals who are the ones with the power to make a real difference,” says Professor Cerin. Members of the said interdisciplinary group includes Dr Duncan Macfarlane, exercise physiologist and Director of Institute of Human Performance, HKU, Dr Janice Johnston, expert in health services and Associate Professor of School of Public Health, Li Ka Shing Faculty of Medicine, HKU, Professor Poh-chin Lai of Department of Geography, HKU, and colleagues from cognate faculties at HKU and other Hong Kong universities.

About the School of Public Health, Li Ka Shing Faculty of Medicine, HKU

The School of Public Health, Li Ka Shing Faculty of Medicine, HKU has a long and distinguished history in public health education and high impact research. With world leading research in infectious diseases as well as on non-communicable diseases of both local and global importance, the School has made significant contributions through its research and advocacy to improve the health of populations and individuals, both locally and globally. The School is a leading research and teaching hub in public health on influenza and other emerging viruses, control of infectious and non-communicable diseases, tobacco control, air pollution, psycho-oncology, behavioural sciences, life-course epidemiology, and health economics, health services planning and management. This work has informed international (e.g. the World Health Organization, Food and Agriculture Organisation of the United Nations), national and local public health policies.

A research brief published by the group of authors at the International Physical Activity and Environment Network is available at http://press.thelancet.com/IPENresearchbrief.pdf.

The research team of the International Physical Activity and Environment Network (IPEN) includes (from left) Professor James Sallis (USA; lead author of the paper), Professor Neville Owen (Australia; senior author of the paper), Professor Ester Cerin (Hong Kong; second author and chief analyst of the paper), Dr Delfien van Dyck (Belgium; co-author of the paper), Professor Josef Mitas (Czech Republic; co-author of the paper), Professor Jaqueline Kerr (USA; co-author of the paper), and Professor Rodrigo Reis (Brazil; co-author of the paper).

Professor Cerin, Visiting Professor of School of Public Health, Li Ka Shing Faculty of Medicine, HKU, pointed out that increased physical activity was strongly associated with neighbourhood features of high residential density, large number of intersections and public transport stops, and more parks within walking distance.