Flash of greater stroke risk when starting oral contraceptives

The risk of prior stroke associated with oral contraceptives and hormone replacement therapy (HRT) decreased to varying degrees after the first year of use, an observational study found.

UK Biobank participants who received contraception had a higher risk of stroke in the first year of use (HR 2.49, 95% CI 1.44-4.30), after which strokes were no longer excessive compared to non-users (HR 1.00, 95% CI). 0.86-1.14), according to the researchers led by doctoral student Therese Johansson, MSc, from Uppsala University in Sweden.

As with HRT, the first year of therapy was associated with an increased risk of stroke (HR 2.12, 95% CI 1.66-2.70), which decreased over the remaining years. However, the risk remained slightly increased over time (HR 1.18, 95% CI 1.05-1.32) even after stopping HRT (HR 1.16, 95% CI 1.02-1.32), Johansson’s group reported in the journal Stroke.

The study supports previous work linking exogenous hormone use and stroke. However, unlike other groups, Johansson and colleagues were able to show that HRT was associated with both ischemic and subarachnoid hemorrhage stroke subtypes.

“The increased rate of ischemic strokes during the first year of use could be the result of an immediate prothrombotic effect of the treatment, which gradually decreases during the remaining years of use due to the adjustment of the hemostatic imbalance,” the authors suggested.

“However, the underlying mechanism by which HRT confers a direct increased risk of subarachnoid haemorrhage is less clear,” they said. “The short-term increased risk could be explained by cerebral vasodilation together with a transient increase in systemic blood pressure after initiation of HRT, leading to rupture of a pre-existing aneurysm.”

HRT is widely used in clinical practice to treat menopausal symptoms and is thought to improve cardiovascular health in some individuals.

Johansson and colleagues reported that the risk of stroke associated with HRT did not change in relation to the onset of menopause. This is consistent with the notion that going through menopause increases the risk of stroke in non-users, but women who have been taking HRT are not at increased risk when they do go through menopause.

Johansson and colleagues found that the small number of strokes recorded in the relatively young cohort of oral contraceptive users precluded analysis by stroke subtype in this cohort.

The study included more than 250,000 women aged 37 to 73 from the UK Biobank. The first occurrence of stroke was tracked in the database, which categorized events as ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage.

The use of oral contraceptives (81%) and HRT (37%) was self-reported by the participants, leaving room for recall bias in the study, Johansson’s group acknowledged.

In addition, this was a relatively healthy population, which limited the generalizability of the results, and the authors could not distinguish between the different formulations of HRT and the oral contraceptives used.

  • Nicole Lou is a reporter for MedPage Today, where she covers cardiology news and other medical developments. consequences


The study was funded by the Swedish Brain Foundation. The work was also funded by the Swedish Heart Lung Foundation, the Swedish Research Council and the Center for Women’s Mental Health, Uppsala University.

Johansson had no details.

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