To identify if tobacco smoking or sociodemographic characteristics are risk factors of rheumatoid arthritis (RA).
From a county RA register 361 patients in the age range 20-79 years were recruited from incidence cohorts with recent disease onset (mean 3.4 years) and compared with 5851 randomly selected individuals from the same population area. Data on selected risk factors were collected by questionnaires (response rate 75 and 59%, respectively) and associations with smoking and risk factors were expressed as odds ratios (OR) with 95% confidence intervals (CI) in a multiple regression analysis.
Age and female sex were, as expected, identified as risk factors of RA. In addition, current smoking was an overall risk factor (OR 1.46, 95% CI 1.10-1.94), in men (OR 2.38, 95% CI 1.45-3.92), especially in men with seropositive RA (OR 4.77, 95% CI 2.09-10.90). Separate analyses revealed no statistically significant risk in women (OR 1.14, 95% CI 0.80-1.62). Low level of formal education, body mass index, marital or employment status were not significantly associated with risk of RA.
Current smoking in men was identified as an independent risk factor for RA, whereas surrogate markers of socioeconomic status were unrelated to the onset of RA.