The United Nations Department of Economic and Social Affairs projects that by the year 2050 there will be more than 9.5 billion people on earth, with the majority concentrated in large cities around the globe.
This growth in population and increasing urbanization is expected to have a significant impact on the incidence of diseases and how they spread.
In addition, there is an increasing prevalence of lifestyle diseases such as cardiovascular diseases (CVD) and diabetes. Now, a series of studies conducted at the University of Melbourne in Australia and published in The Lancet has found a link between city design and disease.
Proactively addressing our growing population
Professor Mark Stevenson, the lead author of the series, explains that over the next three decades, large cities in India will see a greater than 95 percent rise in population and major cities in the United States will see a population growth of more than 30 percent. These dramatic increases will put a strain on infrastructure and public transport systems, forcing more people to drive private automobiles. An increased reliance on automobiles is associated with reduced physical activity, more air pollution, and a greater number of motor vehicle accidents, all of which increase the global burden of chronic disease and injury. The authors have concluded that a proactive approach to changing city design and developing transport systems that encourage walking and cycling is vital.
Prior studies have demonstrated that a compact city model where people cycle or walk to work improves health by increasing physical activity. However, Professor Billie Giles-Corti, co-author of the series, explains that targeting transport infrastructure alone is not enough to counteract the negative impact that rising city populations will have on the health of citizens. A more holistic approach that includes transport, land use, housing, urban design, economic development, public safety, and health services is needed.
The team created a compact city model to estimate the effect that an increasing population will have on the health of its citizens. The model was designed to study the effect of a 30 percent increment in population density combined with diversity in land use. The model also assessed the effect of a 30 percent reduction in travel distance and a 10 percent shift from private cars to walking or cycling. This is a target that some European cities have already set. In Melbourne, for example, the authors estimate that 14 percent of trips in private cars are for distances less than 5 kilometers, a clear indication of the need to encourage walking and cycling and improve public transport.
Models used on most densely populated urban areas of the world
The series authors chose these targets as they can be realistically implemented in the most densely populated cities of the world. The model was applied to Melbourne, Delhi, Copenhagen, London, Sao Paulo, and Boston. In all six cities, physical activity improved and air pollution levels dipped. In addition, the incidence of lifestyle diseases such as type 2 diabetes and cardiovascular disease also fell by 11 percent and 15 percent respectively in Boston, 7 percent and 13 percent respectively in London, and 14 percent and 19 percent respectively in Melbourne. The model acknowledges that there could be a 5-10 percent increase in accidents involving cyclists and pedestrians, but this can be offset by developing transport infrastructure that includes separate lanes for motorized and non-motorized traffic.
The effect of these interventions is projected to be most dramatic in cities that rely heavily on private motor vehicles for transport (London, Boston, and Melbourne are examples), underlining once again the importance of developing strategies that encourage walking, cycling, and public transport. If the infrastructure is concurrently improved to protect pedestrians and cyclists, then the health gains will be real.
In London there was a drop in traffic volume because more people took to cycling.
Some cities like Stockholm and Bogota have already shifted their focus from driving to cycling and walking, and are noticing the health benefits. In London, for instance, while the city's population increased in the decade between 2004 and 2014, there was a 7 percent drop in traffic volume because more people took to cycling.
The team feels more concerted efforts need to be made in cities around the globe to protect citizens from lifestyle diseases. Unfortunately, however, according to series co-author Professor James Sallis of UC-San Diego, city planners and governments continue to ignore the obvious link between city design and disease.
The challenge is to design cities that are geared towards active transport and reduce dependence on automobiles. Such cities will not only improve the health of their citizens, but will be environmentally sustainable in line with the United Nations Sustainable Development Goals.