Smoking Linked to Rheumatoid Nodules in Early Rheumatoid Arthritis

[Anil Tuladhar]

Smoking is strongly associated with rheumatoid nodules in early seropositive rheumatoid arthritis, Swedish researchers report in the May issue of the Annals of the Rheumatic Diseases.

From a cohort of 1589 patients newly diagnosed with rheumatoid arthritis, the team identified 112 with rheumatoid nodules at enrollment. The investigators compared each nodular patient with two matched controls without nodules from the same cohort.

A total of 210 patients completed a detailed questionnaire on tobacco use. Of the responders, 70 were current smokers, 71 were former smokers, and 69 were never smokers. The frequency of current and former smokers was higher in subjects with rheumatoid nodules than in controls (86% versus 59%, respectively). Positivity for rheumatoid factor (RF) was more common in nodular patients than in controls (78% versus 64%, respectively).

"When analyzing the detailed information obtained from the questionnaires and using conditional logistic regression analyses, we found that ever having smoked was associated with an increased risk of the presence of rheumatoid nodules (odds ratio = 7.3; p = 0.001)," lead author Dr. Britt-Marie Nyhall-Wahlin, of Falun Hospital, and colleagues explain.

When the investigators examined smoking duration or smoking amount, they found that the risk of having rheumatoid nodules was not dose dependent.

Only smokers who were RF positive had an increased risk of nodules. The odds ratio for developing nodules for ever smokers was 7.6 for RF positive patients, compared with 1.4 for seronegative subjects.

An association between smoking and rheumatoid nodules was observed among both men and women. No association was found between tobacco use other than smoking and an increased risk of nodules.

While the mechanism by which smoking influences rheumatoid arthritis is unclear, the investigators say, it's possible that it is mediated through increased RF production.