Higher levels of obesity and inactivity, especially among women, explain why arthritis is more common in the United States than in Canada, according to a new study.

Researchers at the Toronto Western Research Institute analyzed 2002-03 data from both countries and found that the prevalence of arthritis in the United States was 18.7 percent and the prevalence of arthritis-attributable activity limitations (AAL) was 9.6 percent. In Canada, the rates were 16.8 percent and 7.7 percent, respectively.

Women in the United States had a higher prevalence of arthritis (23.3 percent) and AAL (13 percent) than Canadian women (19.6 percent and 9.2 percent, respectively). Men in both countries had similar rates of arthritis (14 percent) and AAL (6 percent).

“Our study results suggest that the higher prevalence of arthritis and AAL in the U.S. may be a consequence of greater obesity and physical inactivity in that country, particularly in women,” study lead author Elizabeth Badley said in a news release.

“Public health initiatives that promote healthy weight and physical activity may benefit from including arthritis concerns to its message, and could potentially reduce the incidence of arthritis and AAL,” she concluded.

The study appears in the March issue of the journal Arthritis Care & Research.