A population based nested case-control database (United Kingdom’s General Practice Research Database) study included all women in the database aged 50-79 years (n=955 582) in years 1987- 2006. Exposure to hormone replacement therapy (HRT) was categorised into oestrogens only, oestrogens plus progestogen, progestogen only, and tibolone. Oestrogens were further subdivided according to the route of administration (oral vs transdermal) and dose (low vs high): low dose oral products contained ≤ 0.625 mg of equine oestrogen or ≤ 2 mg of estradiol and; transdermal low dose products contained ≤ 50 μg of oestrogen. There were 15 710 cases of stroke matched to 59 958 controls. The rate of stroke in the cohort was 2.85 per 1000 per year. The adjusted rate ratio of stroke associated with current use of transdermal HRT was 0.95 (95% CI 0.75 to 1.20) relative to no use. The rate of stroke did not increase with the addition of a progestogen to the transdermal oestrogens. The risk of stroke was not increased with use of low oestrogen dose patches (RR 0.81, 95% CI 0.62 to 1.05) compared with no use, whereas the risk was increased with high dose patches (RR 1.89, 95 % CI 1.15 to 3.11). Current users of oral HRT had a higher rate of stroke than non-users (RR 1.28, 95% CI 1.15 to 1.42) with both low dose and high dose.
Date of latest search: 05 February 2016