Oral contraceptive, hormone replacement therapy pose increased stroke risk

The use of oral contraceptive and hormone replacement therapy may put women at heightened risk of stroke, particularly within the first year of use, possibly due to immediate changes in haemostatic balance, according to a study.

A total of 257,194 women from the UK Biobank, born between 1939 and 1970, were included in the analysis. Researchers examined the effect of self-reported oral contraceptive and hormone replacement therapy use in relation to outcomes including any type of stroke, ischaemic stroke, intracerebral haemorrhage, and subarachnoid haemorrhage. They used time-varying variables in Cox regression models.

During the first year of oral contraceptive use, there was a more than twofold increase in the event rate of any stroke relative to nonuse (hazard ratio [HR], 2.49, 95 percent confidence interval [CI] 1.44–4.30), while the risk estimates were comparable during remaining years of use (HR, 1.00, 95 percent CI, 0.86–1.14).

Likewise, during the first year of use, hormone replacement therapy was associated with elevated rates of any stroke (HR, 2.12, 95 percent CI, 1.66–2.70) and cause-specific stroke, including ischaemic stroke (HR, 1.93, 95 percent CI, 1.05–3.57) and subarachnoid haemorrhage (HR, 2.17, 95 percent CI, 1.25–3.78). The rates for any stroke remained high during the remaining years of use (HR, 1.18, 95 percent CI, 1.05–1.31) and after discontinuation (HR, 1.16, 95 percent CI, 1.02–1.32).

The findings provide new insights into the effects of hormone exposure on stroke risk and evidence of not only an overall risk but also pronounced effects in the first year of treatment.