A C.D. Howe study of life expectancy in Canada finds men in the highest earning group can expect to live eight years longer than men who are the lowest earners.

For women, the gap in longevity between the richest and the poorest is much less, just three years. The richest can expect to live to 86, compared to average life expectancy of 83 for poor women.

For men, the highest income earners — roughly the top 20 per cent — have a life expectancy of 83, while the lowest income workers can expect to live to 75.

The study was performed using figures from the Canada Pension Plan for Canadians born between 1923 and 1955.

This kind of study measuring the difference in longevity between rich and poor over a 30-year period has not been performed before, said Kevin Milligan, a fellow in residence at the C.D. Howe Institute and one of the study's authors.

"This is a fundamental aspect of well-being. We talk about income inequality, but this is one of the most fundamental inequalities there is — how long you live, how many years you have with your family," he told CBC News.

Life expectancy improving for all income groups

Life expectancy in Canada has been rising steadily, with men expected to live 7.7 years longer now than they did in 1965 and women expected to live 6.4 years longer.

A key finding of the study is that the longevity gap between rich and poor men has remained fairly constant. Life expectancy for poor and middle income men is moving up at the same rate as it is for the better-off.

This is a contrast to the U.S., where there has been almost no change in longevity for the poorest 20 per cent of the population, yet there are substantial gains for the highest income earners. In the U.S., the longevity gap is 14 years between the richest and poorest.

"Longevity improvements for the low-income people in the U.S. have slowed right down," Milligan said. "This is something with public policy implications that has to be addressed."

Milligan, who is also a professor at the Vancouver School of Economics, said the study could not explain the cause of the steeper curve between rich and poor in the U.S.

The study's authors put forward the theory that a combination of differences in the healthcare system, the Canadian tax and transfer system that leaves more money in the hands of poorer people and differences in lifestyle factors such smoking, diet and exercise might explain the wider gap in the U.S.

Why the gap is smaller for women

He also points to substantial changes in Canadian public policy and employment trends during the lives of the study's subjects, including an influx of women into the workforce and the advent of universal healthcare.

Senior citizens wait to have their eyes examined at a makeshift clinic in the Downtown Eastside of Vancouver. Life expectancy is rising among people of all income levels in Canada. (Darryl Dick/Canadian Press)

He said the findings about the income gap between rich and poor women may be affected by these changes. For example, women may be categorized as having a lower income because they never worked outside the home, but may have lived all their lives in a high-income household.

A woman born in the 1920s is unlikely to have been in the workforce, while a woman born in the 1950s likely worked, he said, meaning the pension data might not offer a fair comparison.

As payments from the Canadian Pension Plan are based on earned income, it would take a different data set than CPP numbers to learn more about the difference between rich and poor women, Milligan said. It's an area that requires further study.

Milligan said the authors cannot point to any causal relationship between higher income and longer life, as there are too many variables in how lower and upper income people may have lived. These include different types of jobs, different education levels and lifestyle choices, such as smoking and diet.