A study released by the American College of Rheumatology suggests that the rheumatoid arthritis rate in women is rising sharply after nearly four decades of steady decline.

Epidemiologists with the Mayo Clinic  in Rochester, Minn., who are tracking trends in the incidence of rheumatoid arthritis, or RA, through the meticulously kept medical records of residents of Olmsted County, Minn., found that the incidence of the disease in women in the study population increased by nearly 50 percent from 1995 through 2004, while the incidence in men remained largely unchanged.

“It was pretty surprising to us,” said Hilal Maradit Kremers, MD, a research associate at the Mayo Clinic Department of Health Sciences Research, who was a co-author on the study.

Dr. Kremers said her team is unsure why the numbers are climbing after dropping steadily since 1955, but she said the methods used to conduct the study point to an environmental factor as the likely cause, rather than increased awareness of rheumatoid arthritis symptoms among doctors and better diagnoses.

The next step, she said, would be more digging to try to identify the cause or causes of the increase, which could be anything from dietary to hormonal changes to chemical exposures.

“There is a need for a fresh look back at this disease because preventing it is better than trying to treat the pain and disability and the other things that come along with it like heart disease and diabetes,” Dr. Kremers says.

Rheumatoid arthritis is an autoimmune disease that progressively attacks the joints, heart, liver and kidneys, causing pain and permanent disability if left untreated. 

at trend, researchers had assumed that the incidence of the disease was continuing to drop in more recent years.

But when Sherine E. Gabriel, MD, a professor of medicine and epidemiology at the Mayo Clinic, and her team began to look at more recent data, the numbers appeared to be going up rather than down. From 1985 to 1994, the incidence of rheumatoid arthritis in the study population was 36.4 per 100,000 women, but from 1995 to 2004, that number increased by nearly half to 54 per 100,000 women. The incidence in men, however, stayed about the same, going from 28.6 to 29.5 per 100,000 over the same two decades.

The Mayo Clinic team said they plan to discuss their findings in greater depth at the annual American College of Rheumatology/Arthritis-Related Healthcare Professionals Scientific Meeting in San Francisco.