Oral contraceptives and rheumatoid arthritis: Further evidence for a preventive effect

To investigate a reported negative association between the use of oral contraceptives (OC) and the development of rheumatoid arthritis, a case-control study was undertaken to compare the histories of OC use between 228 women with a diagnosis of probable or definite rheumatoid arthritis and 302 women with the diagnosis of soft-tissue rheumatism and/or osteoarthritis. The use of OCs before the onset of joint complaints was acknowledged by 31·1% of the rheumatoid arthritis patients and by 55·6% of the controls. After adjustment for possible confounding variables, the rate ratio for ever use became 0·42 (95% confidence interval 0·27-0·65), while it was 0·40 (0·22-0·72) for ex-users and 0·45(0·28-0·75) for current users. These findings confirm the finding from the Royal College of General Practitioners Oral Contraceptive Study that the incidence rate of rheumatoid arthritis among OC users was halved.