After forty years of decline, rheumatoid arthritis (RA) may be on the rise in women, according to recent research. An estimated 1.3 million Americans have RA, and the disease typically affects women twice as often as men.

The overall incidence, or occurrence, of newly diagnosed RA in a given year, declined between 1955 and 1994. Researchers recently set out to examine the incidence, and the prevalence, or number of persons affected by RA in a population at any given time,

The study identified a group of patients with RA (who were at least 18 years old and met the criteria) first diagnosed between January 1, 1995 and January 1, 2005, and a group of patients with prevalent RA on January 1, 2005 living in Olmsted County, Minn.

A total of 350 patients were identified with new-onset RA between 1995 and 2005. Of these patients, 242 were women with an average age of 56.5 years old. Researchers found that the overall incidence of RA was 41.8 per 100,000 people. Among women, the incidence was 54 per 100,000 people, a significant increase when compared to the incidence of 36.4 per 100,000 people in the decade 1985-1994. In contrast, among men, the incidence of RA was 28.6 per 100,000 people, which was consistent with the incidence for men in the previous decade.

The overall prevalence of RA in 2005 was 950 per 100,000 people, which was higher than the 1995 estimate of 850 per 100,000 people.

“Over the past decade, more people have become affected with RA, and we do not yet understand the reasons why,” says Sherine Gabriel, MD, Mayo Clinic rheumatologist and lead author of the study. “This worrisome increase in occurrence of RA not only offers us clues into the causes of RA, but also highlights the need for more research into the causes and treatment of this devastating disease.”

[Source: Newswise]