Risk of ischemic stroke among users of the oral contraceptive pill: The Melbourne Risk Factor Study (MERFS) Group

Abstract

Background and purpose: Use of oral contraceptives has increased, and there is uncertainty about the stroke risk associated with their use. Our aim was to investigate this issue.

Methods: Using case-control techniques, we identified consecutive women with ischemic stroke from 4 Melbourne hospitals. All patients were between 15 and 55 years of age and had no prior stroke. Neighborhood-based control subjects were individually age-matched (+/-5 years) and geographically matched to subject cases. A questionnaire administered to participants elicited information about prior exposure to various potential risk factors, including the oral contraceptive pill (OCP).

Results: We included 234 cases and 234 controls (mean age, 42 years). Compared with noncurrent use, current use of the OCP, in doses of <or=50 microg estrogen, was not associated with an increased risk of ischemic stroke (odds ratio [OR] 1.76; 95% CI, 0.86 to 3.61; P=0.124). Factors associated with an increased risk of ischemic stroke were a history of hypertension (OR, 2.18; 95% CI, 1.22 to 3.91), transient ischemic attack (OR, 8.17; 95% CI, 1.69 to 39.6), previous myocardial infarction (OR, 5.64; 95% CI, 1.04 to 30.61), and diabetes mellitus (OR, 5.42; 95% CI, 1.42 to 20.75); family history of stroke (OR, 2.22; 95% CI, 1.12 to 4.43); and smoking >20 cigarettes per day (OR, 3.68; 95% CI, 1.22 to 11.09).

Conclusions: There was no evidence for an association between ischemic stroke and use of the OCP in low doses (<or=50 microg estrogen) in young Australian women. Other modifiable risk factors such as hypertension, diabetes mellitus, and smoking are important.