The risk of fatal stroke in Finnish postmenopausal hormone therapy users before and after the Women's Health Initiative: A cohort study

•The risk of stroke death in HT users was similarly reduced in the pre- and post-WHI eras.•The discontinuation of HT was accompanied by a significant 33% increase in stroke death risk in the pre-WHI era and a non-significant 32% increase in the post-WHI era within the first post-treatment year, but no longer after 1–8 years.•The change in prescribing policy after the WHI study did not affect the risk of fatal stroke in Finnish HT users.

ObjectiveThe Women's Health Initiative (WHI) study clarified the indications and contraindications for postmenopausal hormone therapy (HT). We studied the impact of the WHI results on the risk of fatal stroke in HT users in Finland.Study designRetrospective analysis setting: Nationwide registers on postmenopausal HT use and causes of death between 1995 and 2009.PopulationWomen ≥40 years (n = 290,272) using systemic estradiol-based postmenopausal HT.MethodsFollow-up started from the first HT purchase during the pre-WHI era (1995–2001) and post-WHI era (2002–2009).Main outcome measuresStroke deaths in HT users were compared with that in the age-matched background population and expressed as standardized mortality ratio (SMR) with 95% confidence intervals.ResultsOverall, 311 HT users died due to stroke. The exposure to HT ≤1 year was associated with a similarly reduced 22% (0.67–0.91) risk of stroke death in the pre-WHI era and in the post-WHI era 27% (0.55–0.94). The risk reductions for HT exposure of 1–8 years in the pre-WHI era (47%, 0.42–0.65) did not differ from that in the post-WHI era (32%, 0.48–0.94). The discontinuation of HT was accompanied by a significant 33% (1.02–1.72) increase in stroke death risk in the pre-WHI era and a non-significant 32% (0.84–1.99) increase in the post-WHI era within the first post-treatment year, but no longer after 1–8 years.ConclusionsThe change in prescribing policy after the WHI study did not affect the risk of fatal stroke in Finnish HT users.