Oral Contraceptives, Hormone Replacement Therapy, and Stroke Risk

Area of Science:

• Endocrinology
• Neurology
• Epidemiology

Background:

• Millions of women use exogenous hormones for contraception and therapy.
• Long-term stroke risk associated with hormone use remains unclear.

Purpose of the Study:

• To investigate the association between oral contraceptive (OC) and hormone replacement therapy (HRT) use and stroke risk.
• To analyze time-dependent and long-term effects of hormone exposure on stroke incidence.

Main Methods:

• Utilized UK Biobank data from 257,194 women (born 1939-1970).
• Examined stroke outcomes (any stroke, ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage).
• Employed time-varying Cox regression models for exposure analysis.

Main Results:

• First-year OC use showed a 2.49-fold increased stroke risk (HR 2.49).
• First-year HRT use increased stroke risk (HR 2.12), including ischemic stroke (HR 1.93) and subarachnoid hemorrhage (HR 2.17).
• Elevated stroke risk persisted during HRT use and after discontinuation (HR 1.16).

Conclusions:

• OC and HRT use are linked to increased stroke risk, especially early in treatment.
• Immediate hemostatic changes may contribute to the heightened risk during the first year.
• Findings emphasize pronounced early treatment effects on stroke risk from hormone therapy.