RISK OF ACUTE CEREBROVASCULAR EVENTS RELATED TO LOW ESTROGEN ORAL-CONTRACEPTIVE TREATMENT

To establish if an association exists between use of oral contraceptiv es (OC) and the occurrence of cerebral arterial thromboembolism, cereb ral venous thrombosis and retinal vein/artery thrombosis, we identifie d all women aged 15-44 years resident in the province of Parma, Italy, who were hospitalized because of a documented cerebral or retinal thr omboembolic event during the period 1989-1993. The numbers of users an d nonusers of OC were estimated from drug sale data and demographic st atistics for the province. There were 21 cases of cerebral arterial th romboembolism during the study period: 10 in OC users and 11 in nonuse rs, for an estimated incidence rate of 1.70 and 0.35 per 10000 woman-y ears OC of use and nonuse, respectively (RR=4.8, 95% CI = 1.8-9.0). Ei ght cases of cerebral venous thrombosis were observed: 6 in OC users a nd 2 in nonusers (both in puerperium), for an incidence rate of 1.00 a nd 0.06 per 10000 woman-years, respectively (RR=16.7, 95% CI = 3.3-81. 4). Finally, 13 cases of retinal vein/artery thrombosis were found: 1 in OC users and 12 in nonusers, for an incidence rate of 0.17 and 0.37 per 10000 woman-years, respectively (RR=0.46, 95% CI = 0.06-3.7). In our population study the use of low oestrogen OC was associated with a n increased risk of cerebral venous thrombosis and ischemic stroke, bu t not of retinal vein/artery thrombosis.