By Lisa Rapaport

(Reuters Health) – Adults who quit smoking decades ago may have a lower risk of rheumatoid arthritis than people who gave up cigarettes more recently, a U.S. study suggests.

Smoking has long been linked to an increased risk of rheumatoid arthritis, and quitting can reduce this risk. But the new study offers fresh evidence that years of cessation can pay off more than just a brief period without cigarettes.

“These results provide evidence for those at increased rheumatoid arthritis risk to quit smoking since this may delay or even prevent the onset of rheumatoid arthritis,” said senior study author Dr. Jeffrey Sparks of Brigham and Women’s Hospital and Harvard Medical School in Boston.

Also, Sparks said by email, while quitting smoking is the best way to reduce rheumatoid arthritis risk, cutting back on smoking “should also help lessen the risk.”

Rheumatoid arthritis is an immune disorder that causes debilitating swelling and pain in the joints. It’s less common than osteoarthritis, which happens when cartilage on the ends of bones wears down over time.

Sparks and colleagues examined up to 38 years of data on more than 230,000 women, including 1,528 who developed rheumatoid arthritis.

Compared to women who never smoked, current smokers were 47 percent more likely to develop rheumatoid arthritis, the researchers report in Arthritis Care and Research.

Current smokers were also 67 percent more likely to develop “seropositive” rheumatoid arthritis –when patients have antibodies in their blood that help identify the disease.

Patients with seropositive rheumatoid arthritis tend to have a more severe disease course with more joint deformities, disability, and inflammation outside of the joints.

Compared to women who quit smoking within the previous five years, women who quit at least three decades ago were 37 percent less likely to develop seropositive rheumatoid arthritis.

The current study wasn’t a controlled experiment designed to prove whether or how smoking might cause rheumatoid arthritis. It also wasn’t designed to show if quitting can directly prevent rheumatoid arthritis.

Women in the study were predominantly white and well-educated, and it’s also possible that results might be different for other groups of people, the study authors note. Smoking was also only assessed every two years, and it’s possible the study missed some changes in smoking habits that occurred between assessments.

But the results should still give smokers yet another reason to quit, said Dr. Kaleb Michaud, a researcher at the University of Nebraska Medical Center in Omaha who wasn’t involved in the study.

“There’s a clear dose-dependency seen between the cumulative amount of smoking and the risks for future rheumatoid arthritis,” Michaud said by email.

“There’s little evidence that smoking cessation reverses rheumatoid arthritis — it’s still incurable and a chronic source of pain and suffering for many people,” Michaud added. “But current smokers could at least reduce this risk by smoking fewer and fewer cigarettes.”

SOURCE: Arthritis Care and Research, online February 21, 2019.