A team of researchers led by Dr. Ruth Ann Marrie of the University of Manitoba looked at health system billing data and death records in that province over a 27-year period covering the fiscal years 1984 to 2011.
They identified nearly 5,800 people with multiple sclerosis and compared them to roughly 29,000 other people who were similar in age, gender, and region of residence. But the people in the larger group did not have MS.
For the people with the neurological disease, the median length of life was 75.9 years. For those without MS, the median was 83.4 years.
Life expectancy for both groups lengthened over the period of the study, Marrie said in an interview.
"There actually was in both groups — MS and the general population — an improvement in life expectancy in people born in more recent years, which is what we've all recognized," she said.
"So we did see an improvement over time. It's just there's still a gap."
Why the difference? The way this study was structured doesn't provide that answer, Marrie said.
She and her co-authors did look at a bunch of other conditions — called comorbidities in medical parlance — to see if they influenced how long people lived; things like heart disease, chronic lung disease, diabetes, depression and anxiety.
Marrie admitted she thought having one or several comorbidities would take a greater toll on people with MS. That wasn't the case.
"That's actually not what I expected to find, but it's a good thing," she said.
The research was done in Manitoba but likely has applicability to other parts of Canada, suggested an MS expert who was not involved in the work.
"MS doesn't shorten life expectancy by much," said Dr. Paul O'Connor, a neurologist and head of the MS clinic at St. Michael's Hospital in Toronto.
O'Connor said the increasing life expectancy for MS patients is at least in part due to the availability of better treatments.
Still, he said, the number of years people with MS might expect to live reveals nothing about the toll the disease takes on quality of life.
Multiple sclerosis can produce a wide and debilitating array of symptoms including balance and mobility problems, difficulty swallowing, cognitive issues, fatigue and more.
"Even if you're not in a wheelchair the fact that you can't see properly, the fact that you can't move properly, that you can't run and you can't go for a walk for several kilometres — these are all major, major negatives for quality of life."
Canada is estimated to have the highest rate of multiple sclerosis in the world. Marrie said the reason for that isn't fully known and is in fact likely a combination of factors.
The research was published in the journal Neurology.