Non-contraceptive hormones and rheumatoid arthritis: possibilities of using a Swedish population-based cohort

We report the possibility of, and the methodological problems associated with, using a large population-based cohort of 23,000 Swedish women, ascertained from a drug prescription database to have received non-contraceptive oestrogens; to further investigate the relationship between such therapy and the postulated protection against development of rheumatoid arthritis (RA). Although this study was primarily designed to look at cancer risk, it should be possible to study the relationship with RA.