Previous studies have found high levels of excess mortality among the homeless compared with the general population, but little information is available on death rates among homeless and marginally housed people living in low-cost collective dwellings, such as rooming houses and hotels.
So, researchers at St Michael's Hospital in Toronto and Statistics Canada compared death rates and life expectancy among a representative sample of homeless and marginally housed people with rates in the poorest and richest income sectors of the general population.
Using data from the 1991-2001 Canadian census, they tracked 15,000 homeless and marginally housed people across Canada for 11 years.
Mortality rates among homeless and marginally housed people were substantially higher than rates in the poorest income groups, with the highest rates seen at younger ages.
Among those who were homeless and marginally housed, the probability of survival to age 75 was 32% in men and 60% in women. This compared to 51% and 72% among men and women in the lowest income group in the general population.
For men, this equates to about the same chance of surviving to age 75 as men in the general population of Canada in 1921 or men in Laos in 2006. For women, this equates to about the same chance of surviving to age 75 as women in the general population of Canada in 1956 or women in Guatemala in 2006.
Remaining life expectancy at age 25 among homeless and marginally housed men was 42 years - 10 years lower than the general population and six years lower than the poorest income group.
For homeless and marginally housed women, remaining life expectancy at age 25 was 52 years â" seven years lower than the general population, and five years lower than the poorest income group.
A large part of this premature mortality is potentially avoidable, say the authors. Many excess deaths were attributable to alcohol and smoking-related diseases and to violence and injuries, much of which might have been related to substance abuse.
There were also many excess deaths related to mental disorders and suicides.
This study shows that homeless and marginally housed people living in shelters, rooming houses, and hotels have much higher mortality and shorter life expectancy than could be expected on the basis of low income alone, they conclude. These findings emphasise the importance of considering housing situation as a marker of socioeconomic disadvantage.