Obesity has been linked to an increased risk of 13 different cancers in women, and where a woman lives can either raise or reduce her risk.

That's what researchers from New York University and Columbia University found when they followed more than 14,200 women in the New York University Women's Health Study for about 24 years. By getting more exercise, those who lived in more walkable neighborhoods had a lower risk of obesity-related cancers, particularly postmenopausal breast cancer, than those who lived in less walkable neighborhoods.

“The long-term follow-up allowed us to study the effects of walkability with potential long latency periods of cancer. We were also able to measure walkability as participants moved around the country during follow-up,” Yu Chen, corresponding author on the study, told TheDoctor.

By getting more exercise, those who lived in more walkable neighborhoods had a lower risk of obesity-related cancers, particularly postmenopausal breast cancer.

The concept of walkability comes from the field of urban design, Andrew Rundle, another of the co-authors of the study, explained, and the findings support policies that encourage the development of walkable neighborhoods in urban areas.

Neighborhood walkability can be measured in a few different ways. Here are the measures that Rundle says are often used:

  • Population density. The higher the population density, the more walkable a neighborhood is because things are just closer together.
  • Proximity to frequent destinations. For example, people who live two blocks from the grocery store or their church will probably walk to those places. As Rundle put it, “The proximity of destinations that people use on a regular basis increases the likelihood they will walk there.”
  • The way streets are laid out. Street networks that are laid out on a grid are more walkable than a design with cul-de-sacs. They make it easier to get places.
  • Reliable public transportation. Having access to buses, subways and light rail systems makes people less isolated and dependent on their cars, so they start walking more places.

During the years of follow-up, the researchers measured the walkability of each woman's residential neighborhood and then looked at the association between walkability and overall cancer risk, as well as her risk of specific obesity-related cancers such as postmenopausal breast cancer, endometrial cancer, ovarian cancer and multiple myeloma.

By the end of 2016, 18 percent of participants were diagnosed with an obesity-related cancer for the first time: 53 percent with postmenopausal breast cancer, 14 percent with colorectal cancer and 12 percent with endometrial cancer.

They found that living in a more walkable neighborhood offered protection against the risk of obesity-related cancers in women. The connection between walkability and a lower risk of obesity-related cancer was especially strong among women living in lower income neighborhoods.

The researchers don't yet know how that contribution affects disease risk, said Rundle, a professor of epidemiology at the Columbia University Mailman School of Public Health, but it is the kind of thing the researchers would like to study next, along with walkability's impact on diabetes and Alzheimer's disease and dementia. “The study population is aging: they are now between 70 and 100 years old,” Chen, a professor of epidemiology at the NYU Grossman School of Medicine, explained. “Women who live in a more walkable neighborhood earlier in their life may be less likely to develop these aging-related conditions.”

The study is published in the journal Environmental Health Perspectives.