Though cities can seem stressful, hectic, and potentially dangerous, there are certainly positives: they bring working, living, and socializing closer together, cutting down on cars and car journeys, and promoting walking and active transport. So while the stress might seem overwhelming if you aren’t used to it, the act of living in a city can actually be quite beneficial to your health–if the city is designed the right way
That’s the conclusion of a major new study looking at the relationship between different levels of housing density and long-term health outcomes. It finds that suburban places, with their car-centric transport and more spread out design, make people less healthy over time, compared to city centers.
In short: despite their endless stress and hustle-bustle, cities may not be as bad for you as you thought.
The longitudinal study, from researchers in the U.K. and Hong Kong, makes use of a unique dataset of about 500,000 people, ages 37 to 73, living in 22 British cities. It looks at the association between housing density and levels of body-mass index (BMI), waist circumference, whole body fat, and obesity–important indicators and markers for a series of serious health problems.
The big finding: housing densities of less than 1,800 units per square kilometer, including those in suburbia, increase the chances of someone being obese by about 10%. The researchers argue that lower-density development encourages sedentary behavior, including driving to stores and work, and less cycling and walking.
The average housing density in the U.S. is about 1,200 units per square kilometer. Defined as BMI above 30, obesity is associated with higher risk of diabetes, heart disease, and other cardiovascular problems.
By contrast, people living in areas above an 1,800 units per kilometer density threshold have a roughly 10% lower chance of being obese, the study finds. That includes inner cities where people are more likely to live in apartment blocks and smaller terraced homes, and where walking to work and for shopping is normalized.
In an interview co-author Chinmoy Sarkar says that the 10% increase or decrease in obesity risk may not sound like a lot. But, extrapolated to a whole city or country, it may be a very big deal. “Urban interventions are all pervasive. They affect all the people living in that city. They might prevent several billions of health costs,” says Sarkar, an assistant professor with the Healthy High Density Cities Lab at the University of Hong Kong.
Using the same dataset, Sarkar also looked recently at green spaces and obesity levels. It also found an improvement in obesity in places with more green vegetation cover, though again the effect was relatively small. Sarkar cautions the results may not be generalizable. He also still has to work out whether cities are better off having a few major parks, or whether lots of green spaces through a city work better from a health point of view.
The main study shows that the relationship between health outcomes and density is not linear. You can have too much city-living for your own good. On the one hand, higher density leads to more walking on average, more social interaction, and better access to services, like healthcare. But when cities become too crowded the positive health benefits tail away. It’s not as though a slum, where there are too many people, is healthier than a well-planned urban area, with space to move around.
Previous research has shown that installing new transit stations can promote walking and improve health, and that rates of obesity increase in areas where people are exposed to high numbers of fast food outlets. But Sarkar says the field of healthy urban planning is still at an early stage. His models don’t yet have predictive value, such that you could, say, predict the health outcome of a new shopping mall.
“We would like to reach a stage where you have different urban design parameters in terms of density and accessibility and different scenarios of [personal] health risk. Then we could predict the health outcome,” he says.