The protective effect of the oral contraceptive pill on rheumatoid arthritis: an overview of the analytical epidemiological studies using meta-analysis.

Department of Epidemiology and Rheumatology, St. Bartholomew's Hospital, London.

PIP: In 1978 the Royal College of General Practitioners reported results from their oral contraceptive study which demonstrated a protective effect of use of oral contraceptive pills on the development of rheumatoid arthritis (RA). Since this publication, 10 additional studies have been reported with differing results and conclusions, so the studies were reviewed and a meta analysis was carried out. In all, 9 independent studies, including 6 case-control and 3 prospective studies were included in the meta analysis. The method described by Yusuf et al. for pooling of clinical trials was used. In addition, the graphical "odd man out" technique as described by Walker at al. was also used to estimate the summary confidence interval (CI) for the underlying estimate of relative risk as well as to test for heterogeneity of the studies. The overall pooled adjusted odds ratio for the case-control studies was 0.60 (95% CI: 0..48-0,75), while the overall pooled adjusted relative risk for the prospective studies was 0.88 (95% CI: 0.70 - 1.12); the overall pooled adjusted risk ratio for all studies combined was 0.73 (98% CI: 0.62-0.85). The "odd man out" method produced a summary 94% confidence interval of 0.70-0.72. the pooled risk ratio for the 5 former studies was 0.49 (95% CI: 0.39-0.63) compared to a pooled risk ratio of 0.95 (95% CI: 0.78 - 1.16) for the latter 4 studies. This results show that OCPs may not have a protective effect on the development of RA, but rather may prevent the progression from mild to severe disease by modifying the disease process, thus the potential disease-modifying effects of sex hormones in patients with incipient RA should be examined.

PMID: 2819342 [PubMed - indexed for MEDLINE]