To examine whether smoking is a risk factor for rheumatoid nodules in early rheumatoid arthritis, and if so to determine the quantitative effect of smoking.
From a cohort (n = 1589) in a structured programme for follow up of newly diagnosed cases of rheumatoid arthritis (symptoms of swollen joints < or =12 months), 112 individuals with rheumatoid nodules at inclusion were identified. Nodular patients were each compared with two age and sex matched controls without nodules from the same cohort. A detailed self administered tobacco use questionnaire was answered by 210 patients (63%).
Seventy patients were current smokers, 71 former smokers, and 69 had never smoked. Current smoking and former smoking were more common in patients with rheumatoid nodules compared with controls (86% v 59%) in both sexes. Positive rheumatoid factor (RF) was found more often among cases with nodules than controls (78% v 64%). Using detailed information from the questionnaires with conditional logistic regression analyses, ever having smoked was associated with an increased risk of the presence of rheumatoid nodules (odds ratio (OR) = 7.3 (95% confidence interval, 2.3 to 23.6); p = 0.001). The risk of having nodules was not obviously dose dependent when smoking duration as well as smoking amount were examined. A stratified analysis showed that only RF positive smokers had an increased risk of rheumatoid nodules. Smoking was associated with rheumatoid nodules among both men (p = 0.006) and women (p = 0.001). Tobacco use other than smoking (n = 31) was not associated with an increased risk of nodules (OR = 0.8 (0.2 to 3.4); p = 0.813).
There is a strong association between smoking and rheumatoid nodules in early seropositive rheumatoid arthritis.