An Alarmingly Strong Link Between Lack of Walkability and Diabetes
Many urban planners and activists subscribe to the central belief that a walkable neighborhood is a healthier one, quite literally. After all, if you have the choice to stroll to school, or the corner store, or even just the nearest bus stop, all those steps add up over time, amounting to a more active lifestyle than is possible at the end of a cul-de-sac.
Science, however, has been a bit slower to prove this point with hard data, particularly as researchers have been making the fairly massive shift in philosophy toward recognizing the places where we live as a key determinant in our health. Now, a new study out of Toronto just published online in the journal Diabetes Care, adds yet more compelling evidence.
Researchers at St. Michael's Hospital and the Institute for Clinical Evaluative Sciences examined data from more than one million residents of Toronto and concluded that people who lived in less walkable neighborhoods were significantly more likely over time to develop diabetes. The effect was particularly strong for immigrants to the city, many of whom live with a high-risk combination of genetic predisposition to diabetes, poverty and poor walkability. In the most startling finding, the study found that a new immigrant in a less walkable neighborhood was more than 50 percent more likely to develop diabetes than a long-term resident of Toronto living in one of the most walkable areas, regardless of neighborhood income.
The study looked at just about everyone in Toronto aged 30-64 – the population experiencing the most rapid rise of diabetes incidence – and singled out those who did not have diabetes as of March 31, 2005. The study followed these people over the next five years: in all, 1,239,262 of them, including 214,882 who appeared to be recent immigrants based on registration in the province’s healthcare plan.
By March of 2010, 58,544 of these people had developed diabetes. And the walkability of the communities in which they lived turned out to be closely linked to that outcome (given the complex factors that affect health, the researchers acknowledge that they can’t definitively say this relationship is directly causal).
As a side note, this study is also a great eye-opener to the type of research that’s possible within a nationalized healthcare system, where you don’t have to account for health outcomes skewed by access to care (in the U.S., amid all the other variables stacked against their health, low-income families also often lack insurance), and where it’s possible to comprehensively cross-reference health data with metrics from other sources like the census. As the researchers explain: “Health records for each individual in our cohort were linked anonymously across datasets using an encrypted version of their health card number.”
The researchers were further able to link this health data to the postal codes of individual residences, which were used in determining walkability (this tactic passed ethical muster with the hospital’s review boards, in case you’re wondering). The researchers also developed their own walkability index assessing population and dwelling density, street connectivity and the availability of nearby retail and service destinations.
This chart sums up the key findings, broken down by group. The white squares represent low-income recent immigrants; the black circles low-income long-term residents; the black squares high-income recent immigrants; and the white circles high-income long-term residents.
For all of these groups, the incidence of diabetes drops for people living in the most walkable neighborhoods. But the gap between them is most striking (and also speaks to the variable of poverty). The authors note that the majority of immigrants to Toronto – one of the world’s most multi-cultural cities – come from South Asia, East Asia, and Africa, and these are also groups that are particularly susceptible to the development of diabetes.
Public health researchers have become increasingly alarmed by the incidence of diabetes in developing countries in these parts of the world, where, the Toronto authors write, “the rise in diabetes seems to be intricately linked to shifts in urbanization.”
In this context, however, they’re talking about a specific form of urbanization: the kind that mimics post-World War II Western growth patterns and lifestyles.
The Toronto study highlights that within urbanized areas, the impact of neighborhoods on public health can vary significantly. And so there’s hope for applying this lesson in the parts of the world that have yet to urbanize, as well as within cities like Toronto as they continue to grow. It’s no coincidence that the least walkable neighborhoods identified in this research were often the most recently developed. Unlike their older counterparts, they had large blocks instead of smaller ones, sprawling development instead of density, separated land uses instead of mixed ones.
The doctors and public health researchers behind this paper noted all of these differences, sounding remarkably like urban planners themselves. Reaching across disciplines, they conclude: “the way we structure and build our cities will play an increasingly greater role in shaping the health of the world’s population.”