Smoking is a significant risk factor for seropositive rheumatoid arthritis, and quitting may delay or even prevent the disease, a study has found.

American Heart Association

In a paper published in Arthritis Care & Research, researchers report the analysis of data from 230,732 women – including 1,528 individuals with rheumatoid arthritis – participating in the Nurses’ Health Study (NHS) and NHS II.

They saw that current smokers had a significant 67% increased risk for seropositive rheumatoid arthritis (RA), compared with never smokers, while those who smoked 25 or more cigarettes per day had a 92% higher risk.

There was an increasing trend of association between pack-years of smoking and seropositive RA such that 35 pack-years of exposure was associated with a 2.3-fold higher risk for seropositive RA, compared with never smokers (P less than .0001).

Xinyi Liu of the division of rheumatology, immunology, and allergy at Brigham and Women’s Hospital, Boston, and her coauthors noted that the population attributable risk of RA from smoking was 14% and that smoking could contribute up to 35% of seropositive RA risk.

“Although the biologic mechanisms linking smoking with increased risk for developing RA are still not clear, components in cigarette smoke, such as nicotine, hydrocarbons, and carbon monoxide, are known to have aberrant effects on the immune system,” the authors wrote.

The good news was that sustained smoking cessation significantly reduced the risk of RA and seropositive RA, and those benefits increased with the amount of time since the individual stopped smoking.

Women who had quit smoking at least 30 years prior showed a 22% lower risk of all RA and a 37% lower risk of seropositive RA, compared with those who had quit within the previous 5 years. However, even 30 years after quitting, there was still a 30% higher risk of seropositive rheumatoid arthritis, compared with the risk among women who had never smoked.

“While smoking cessation may not decrease RA risk to the level of a never smoker, our findings provide evidence that a behavior change of smoking cessation may delay or even prevent the onset of seropositive RA,” the authors wrote. “These results could provide rationale for a smoking intervention trial among active smokers to prevent the formation of RA-related autoantibodies or to prevent the progression to RA among those at elevated risk for seropositive RA.”

Commenting on the difference in associations with seropositive and seronegative rheumatoid arthritis and smoking behavior, the authors wrote this suggested these two types of the disease may represent separate phenotypes with different risk factors.

The National Institutes of Health supported the study. No conflicts of interest were declared.

SOURCE: Liu X et al. Arthritis Care Res. 2019 Feb 21. doi: 10.1002/acr.23837.