The influence of oral contraceptives on the risk of multiple sclerosis

Objective To examine the risk of multiple sclerosis in users of combined or al contraceptives. Design Cohort study conducted between 1968 and 1996 using diagnostic data s upplied by general practitioners Setting General practices throughout the United Kingdom. Population Royal College of General Practitioners' Oral Contraception Study cohort of initially 46,000 women recruited during the late 1960s. Methods Directly standardised incidence rates of multiple sclerosis were ca lculated for current, former and never-users of oral contraceptives using f irst ever cases of multiple sclerosis reported by the general practitioners . The standardisation variables were age,parity, social class and smoking h istory. Five-year survival rates in the different contraceptive groups were calculated using standard life table techniques. Results One hundred and fourteen first ever cases of multiple sclerosis had been reported by November 1996 during 564,000 woman-years of observation. The incidence rate in both current and former users was not materially diff erent to that in never-users. Although based on limited evidence there was no suggestion that the five-year survival was affected by a woman's use of combined oral contraceptives. Conclusions These findings do not suggest a greatly elevated risk of multip le sclerosis during, or after, use of combined oral contraceptives.