1414Hormone replacement therapy, oral contraceptives and stroke risk

Abstract

Abstract Background Millions of women use exogenous hormones as hormone replacement therapy (HRT) or oral contraceptives (OC). Still, time-dependent and long-term consequences of exogenous hormones on cerebrovascular health remains unclear. Methods We examined the effects of HRT and OC usage on stroke risk in 256,661 women from UK Biobank, born between 1939 and 1970. Outcomes included any type of stroke, ischemic stroke (IS), intracerebral hemorrhage (IH), and subarachnoid hemorrhage (SH). Exposures were analyzed as time-dependent variables in Cox regression models. Results are expressed as hazard ratios (HR) with 95% confidence intervals. Results During first year of exposure, HRT usage was associated with higher hazard rates of any stroke (HR = 2.12[1.66-2.70]), IS (HR = 1.93[1.04-3.56]) and SH (HR = 2.14[1.23-3.72]) compared to non-usage, which remained significant only for any stroke during remaining years of exposure. Similarly, we observed an increased hazard of any stroke during first year of OC exposure (HR = 2.29[1.34-3.92]), while the hazards were found to be comparable during remaining years of use (HR = 1.03[0.92-1.17]). Conversely, women who previously had been exposed to OC, had a lower hazard rate of any stroke later in life, (HR = 0.88[0.82-0.94]). Conclusions Our findings suggest that HRT and OC use cause immediate changes in hemostatic balance, therefore increasing the short-term stroke risk. However, long-term effects of OC use during reproductive years might improve cerebrovascular health and prevent stroke events later in life. Key messages HRT usage increase the risk of stroke, both short-term and with longer use, while the increased stroke risk might be limited to the first year of OC use.