Objective: To evaluate exposure to external factors associated with risk or prevention of rheumatoid arthritis (RA).
Methods: Two hundred and ninety-three incident cases of RA and 1346 population-based referents were included in a case-referent study, in which previous exposure experiences were collected through a postal questionnaire.
Results: An inverse association between RA and additional schooling after compulsory school was seen for men. Current smoking was associated with significantly increased risks of RA for men and women [odds ratio (OR) 2.9, 95% confidence interval (CI) 1.4-6.4, and OR 1.8, 95% CI 1.1-2.9, respectively], as was previous smoking for men (OR 2.3, 95% CI 1.2-4.4). There were also indications of relationships between previous use of a private well and RA in both men and women.
Conclusion: Several previously published associations have been reproduced in the present study, which also generates some new hypotheses that suggest further research.