TORONTO - Canadians living in homeless shelters and rooming houses have a much shorter life expectancy than the general population - and poverty is not the only factor contributing to their premature deaths, researchers conclude.

In a 10-year study, researchers found the chance of surviving to age 75 among the homeless or inadequately housed is 32 per cent for men and 60 per cent for women, compared to 51 per cent and 72 per cent respectively for the lowest income group in Canada's population.

To put that in perspective, the probability that a 25-year-old man living today in marginal housing would make it to age 75 is equal to the life expectancy of the average young male in 1921 - long before the advent of antibiotics and other life-saving treatments.

For homeless or poorly housed females, their chance of surviving to 75 is the same as women in the general population of Canada in 1956.

"Even compared to the poorest one-fifth of the Canadian population, people living in shelters, rooming houses and hotels had a much lower probability of survival," said lead researcher Dr. Stephen Hwang, an internal medicine specialist at St. Michael's Hospital in Toronto's downtown core.

"In fact, the men living in rooming houses are four times more likely to die (prematurely) than people in the general population."

There are many factors that contribute to a lower life expectancy, said Hwang, noting that illnesses linked to alcohol and drug abuse, as well as tobacco-related diseases, are "greatly increased in this population."

"For people living in these marginal housing situations, their access to care and the control of their chronic conditions is worse than in the general population," he said, explaining that poorly managed high blood pressure and diabetes can dramatically ratchet up the risk of death from heart attack and stroke.

Those in shelters and rooming houses often suffer from mental illnesses and suicide is more common. Exposure to deadly violence also occurs more often when compared to the general population, he said.

"I guess violence and injury travel with poverty, and so the individuals are more than just poor, they're living in ... situations that probably further increase the risk (of death)."

The study, published online Monday by the British Medical Journal, looked at 1991 census data on 15,100 people of varying ages across Canada, who reported being homeless or living in rooming houses or hotels.

Using death records, the researchers determined 3,280 had died in the next 10 years, allowing them to calculate mortality rates and life expectancy for different age groups.

While most people may realize that being homeless and relying on shelters can put one's health and life at risk, Hwang said those residing in rooming houses and low-end hotels are just as disadvantaged.

Based on his experience treating patients, he said it's often easier for people in shelters to access medical care because staff will see a person looking ill and send them to a hospital or bring in a doctor or a nurse.

"Rooming houses and other marginal housing situations are kind of a hidden world. You can be on death's door in a room in your rooming house and no one may know that."

Hwang said the study's findings are a de facto call to government to ensure that all citizens have "decent and affordable housing."

"If you improve the housing situation of these individuals, would their chance of dying decrease? Our study doesn't directly tell us that it would make a difference, but I believe that it would."

James Frankish, director of the Centre for Population Health Promotion Research at the University of British Columbia, called the study "interesting and important."

"It raises very interesting questions about this Pandora's box of chronic disease in low-income, marginalized people," he said from Vancouver. "It's not just being poor, it's something about their social conditions, the actual physical environment in which they live."

Improving the health and life expectancy of people on the bottom rungs of society isn't just about providing a roof over their heads, but also about helping them with social reintegration - getting involved in community, working if they can, going back to school and connecting to others, he said.

"This study ... clearly shows that we're putting ... pretty ill people in pretty marginalized housing. And then what?"

"They're either going to die an untimely death, which this study shows that they do, or they often end up having very expensive and inappropriate use of the health system, because they don't have physicians, they don't have GPs. They use the emergency ward, which is a really expensive way to get care. Or they don't get any care until they're really sick and then they have to be hospitalized."

"As Canadians, what are we prepared to do about it?"