A new study that tracks the frequency of cardiac arrest in Toronto neighbourhoods has researchers at St. Michael's Hospital looking at what factors could be at work, from walk-ability and the amount of green space to affluence.
The study mapped the addresses of more than 5,000 participants who had suffered cardiac arrest outside of a hospital. It found that those living in southwest and central Scarborough, western parts of North York and north Etobicoke had the highest rates of cardiac arrest – about 500 per 100,000, over three times higher than the lowest-rate areas: north Scarborough, downtown Toronto, East York and the northeast part of North York.
"One of the things we thought was very surprising about this study was the fact that there are areas that have very, very high [rates of cardiac arrest] adjacent to very, very low," Katherine Allan, a PhD student at the University of Toronto and the lead investigator of the study, explained.
The study focused specifically on cardiac arrest – when the heart suddenly stops beating, as opposed to a heart attack, where the heart experiences a blockage that prevents it from getting enough oxygen. It is based on the City of Toronto's neighbourhood maps.
Increasingly, scientists in Canada, the U.S., UK and elsewhere are mapping the spread of diseases on a micro-geographic level – looking to social determinants of health neighbourhood by neighbourhood. Some argue that urban polarization makes for big differences in health outcomes in small areas.
A 2011 study done by the Direction de Santé Publique de Montréal found men in poorer neighbourhoods lived a almost 11 years less than their counterparts in wealthier areas. The study found people in better-off neighbourhoods go longer without disabilities, and are far less likely to have their babies die shortly after birth. Children and teenagers in poor neighbourhoods die at twice the rate of youth in rich areas.
In the St. Michael's study, Ms. Allan referenced one area in particular – around Victoria Park Avenue, west of Scarborough – where a neighbourhood showing very high risk for cardiac arrest was found directly across the street from one that showed a very low risk.
"That's intriguing," she said. "We're just starting to figure out why it's in particular neighbourhoods and what exactly about those neighbourhoods is contributing to those risks."
To figure out why these trends appeared, Ms. Allan and her team are looking at factors that may contribute to a higher risk of cardiac arrest, such as income and education. They discovered higher levels of education and higher incomes in a neighbourhood correlated with a lower risk of cardiac arrest. But they want to know what other factors could contribute to this trend and are currently looking at everything from ethnicity to the physical characteristics of a neighbourhood.
"We're looking at walk-ability of a neighbourhood, how accessible a neighbourhood is, if there's green space," she said.
Still, discovering what factors lead to cardiac arrest is a lofty goal, according to Paul Dorian, a cardiologist at St. Michael's who supervised the research. Mr. Dorian explained cardiac arrest strikes suddenly and severely because people who have heart disease often don't realize it until it's too late.
"It's kind of like going over a waterfall," he said. "You really wouldn't know that you're about to go over a cliff until this event happens."
But Ms. Allan stressed the study wasn't intended to alarm anybody, even those who live in high-risk neighbourhoods.
"If somebody figures out they live in an area of high cardiac arrest rates, they shouldn't move, and they shouldn't be worried they're going to drop dead the next day," she said. "Everyone's risk is different based on their lifestyle, health status and genetics."
Sheryl Gill, an ambassador for the Heart and Stroke foundation, suffered cardiac arrest when she was 38. Now, she wants people to know what to look for so they can protect themselves and help others in an emergency.
Unlike a stroke or heart attack, those suffering from cardiac arrest simply collapse to the ground, Ms. Gill said. She urged passersby to call 9-1-1 and, if they're trained, to perform CPR.
"It's about paying attention and doing something."
With a report from Anna Mehler Paperny