It suggests the price tag for all this hospital time is substantial, about $1.8 billion a year.
The unhealthy behaviours studied in the report are smoking, excess alcohol consumption, poor diet and physical inactivity.
The researchers found what is called a dose effect — the more one indulged in one of these behaviours, the more days that person spent in hospital.
The work was done by researchers at Toronto's Institute for Clinical Evaluative Sciences and the Ottawa Hospital Research Institute.
It is being presented at the annual meeting of the Canadian Public Health Association, underway in Toronto.
The researchers have created an online calculator which people can use to estimate their own life expectancy based on how they fare with these four unhealthy behaviours. The tool even allows users to calculate their chances of living until an important future event, such as the marriage of a grandchild, the person's 100th birthday, or the Toronto Maple Leafs winning a Stanley Cup.
Senior author Dr. Doug Manuel said the purpose of the website was to bring home to individuals how these behaviours affect their lives, not just the health-care system they pay for.
The study looked at the health behaviours of nearly 80,000 people from Ontario aged 20 to 79, linking it to the same individuals' health-care usage records.
They estimated that a sizable portion of the days Ontario residents spend in hospital can be linked to smoking, poor diet, excess drinking, lack of physical activity or a combination of those behaviours.
"One in three people in hospital are there because of their unhealthy living. In Ontario, that adds up to 940,000 patient days per year or $1.8 billion," said Manuel.
"I'm always struck by the magnitude, the size. It always does take us back a step. But it's because these health behaviours affect everything."
Manuel said the cost figure would vary from province to province but the one in three figure is probably comparable across the country.
These poor health habits are common; only 7.2 per cent of people in the study reported having none of these unhealthy behaviours. The largest proportion of men — 35 per cent — reported having two of the four behaviours. The largest proportion of women, 39 per cent, reported having one.
People with the unhealthiest behaviour spent 280 per cent more days in hospital than people at the other end of the behaviour spectrum. For example, a 54-year-old with the unhealthiest behaviours in all four categories spent as much time in hospital as a 74-year-old with none of the risks.
Smoking had the biggest influence on hospital days of all four behaviours, followed by physical inactivity, poor diet and excess drinking.
The life expectancy calculator can be found on the Big Life Health Calculators website at www.projectbiglife.ca/life/
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