Oral contraceptives and stroke.

Area of Science:

• Neurology
• Epidemiology
• Pharmacology

Background:

• Over 25 studies since 1962 have investigated the link between oral contraceptives (OCs) and stroke.
• Epidemiological studies, primarily case-control and cohort designs, are the main source of data.
• These study designs have inherent limitations and potential biases.

Purpose of the Study:

• To synthesize findings from epidemiological studies on oral contraceptive use and stroke risk.
• To identify factors influencing the relationship between OCs and cerebrovascular events.
• To assess the overall risk-benefit profile of low-dose oral contraceptives.

Main Methods:

• Systematic review and synthesis of existing epidemiological research on OCs and stroke.
• Analysis of stroke risk stratified by estrogen content and presence of co-existing risk factors.
• Evaluation of data concerning cerebral venous thrombosis (CVT) associated with OC use.

Main Results:

• High estrogen content (≥50 µg) in OCs is associated with increased risk of all stroke subtypes and stroke mortality.
• Low estrogen content (<50 µg) OCs present a very low or negligible stroke risk.
• OC use significantly elevates cerebral venous thrombosis risk, especially with congenital thrombophilia.
• Associated risk factors like hypertension, smoking, and migraine substantially amplify stroke risk with OCs.

Conclusions:

• Low-dose oral contraceptives have a very low stroke risk, particularly when risk factors are controlled.
• The benefits of low-dose OCs generally outweigh the risks for most users.
• Further research is needed on progestogen-only contraceptives and their stroke risk profile.