THE RISK OF SERIOUS ILLNESS AMONG ORAL-CONTRACEPTIVE USERS - EVIDENCEFROM THE RCGPS ORAL-CONTRACEPTIVE STUDY

Background. So far, no-one has attempted to evaluate the overall balan ce of serious, but not necessarily fatal, disease among a cohort of or al contraceptive users. Aim. To emprirically assess the balance of ris k of serious illness among a cohort of oral contraceptive users follow ed up for up to 28 years. Methods. Oral contraceptive-associated serio us disease was defined as that which is often life-threatening and/or associated with long-term disability, and which has been found, or pos tulated, to be associated with use of combined oral contraceptives. Da ta from the Royal College of General Practitioners' (RCGP) Oral Contra ception Study were examined to determine the rate of such conditions d uring 335 181 woman-years of observation in 'ever users' and 228 727 w oman-years in 'never users'. The rates were standardized for age, pari ty, social class, and smoking. Results. Compared with never users, eve r users had a small increased risk of any serious disease (relative ri sk = 1.17; 95% confidence interval = 1.09-1.25). Ever users had an exc ess risk of cerebrovascular disease, pulmonary embolism, and venous th romboembolism, and reduced risk of ovarian and endometrial cancer. The increased risk was seen only in younger women; by the age of 50, ever users had the same risk as never users. The risk appeared to be confi ned to women using older oral contraceptives containing 50 micrograms or more of oestrogen. Conclusions. Past users of older, higher dose or al contraceptives can be reassured that the small increased risk of se rious disease seen during current use does not persist after stopping, and that latent effects do not appear later in life. Currently availa ble oral contraceptives, containing less than 50 micrograms of oestrog en accompanied by the progestogen, levonorgestrel, or norethisterone a cetate, do not appear to be associated with an increased net risk of s erious disease.