A survey has found that Canadians have less arthritis and less arthritis-related disability than Americans, probably because our neighbors to the north are leaner and more physically active, researchers say.

The results of the survey, part of the Joint Canada/United States Survey of Health, which were published in the March issue of Arthritis Care & Research, revealed that the rates for arthritis in the U.S. were about 2 percent higher than in Canada – 18.7 percent compared to 16.9 percent.

And more people said that arthritis limited their daily activities in the U.S. – 9.3 percent compared to 7.4 percent in Canada.

“What accounts for the difference in the two is the higher proportion of obesity and inactivity in America, particularly among women,” says Elizabeth Badley, PhD, an epidemiologist at the University of Toronto.  “I think that’s surprising.”

In the survey, 14 percent of Americans who reported having arthritis were also obese. That number went up to 20 percent when they reported being disabled by arthritis. Among Canadians, 13 percent of those with arthritis reported being obese and 17 percent who reported arthritis-related disability were obese.

Perhaps the biggest difference between the two countries, however, had to do with physical inactivity. Americans with arthritis were nearly three times as likely to report not getting any exercise as Canadians with arthritis.

“It’s particularly American women who are not doing very well actually. American men and Canadian men are not that different," Badley says. “American women tend to be more obese and more physically inactive than Canadian women. And quite why that is I don’t know.”

“But we have nothing to be complacent about in Canada. Obesity is growing as it is in the United States and a lot of the population is physically inactive. I think it’s a western world phenomenon. It’s not just a United States phenomenon,” she continues. “We have nothing to be complacent about, but that few percentage points made a difference. “

Eric Matteson, MD a professor of medicine and rheumatology at the Mayo Clinic in Rochester Minnesota, says researchers only looked at arthritis as a general term, but he says this is a good study because you can see similar factors at work across two countries.

“It helps us to affirm the biological plausibility of the hypothesis that a certain risk factor like obesity is associated with arthritis and gives us a starting point to prevent it,” Dr. Matteson says.

Researchers stress the numbers in both countries are high and point to the need for public health initiatives to encourage people to lose weight and increase their physical activity.

“The take home message is, being physically active and keeping a normal weight is actually important and this shows up in the amount of arthritis there is in the population,” Badley says.

“Promoting physical activity and a healthy weight in America – it’s really important that we do this. And also that people with arthritis aren’t missing out. They can and should still exercise,” Badley continues. “If they have such bad knees they can’t do their exercise, it’s probably way overdue to think about a joint replacement. There is a strong literature that shows the benefit of exercise."

Dr. Matteson agrees. “For the American audience it shows that we really do need to be more physically active if we want to avoid these problems and for people in both countries, it’s telling them a significant portion of our population is inactive and overweight and we have significant health consequences from that."

Researchers admit this study did not address the issue of race because they did not have comparable data in the two countries. Dr. Matteson says this is a downside of the study.

“I think that is unfortunate that they weren’t able to adjust for race because that has been associated in some studies. At least in the United States, there are studies looking at the effects of occupation, race, obesity in development for example of knee arthritis.”

Researchers say they also weren’t able to determine what effect insurance coverage has. Canada has universal health coverage for its citizens and the researchers say financial trouble could keep some Americans from getting care.