Route of HRT administration may affect stroke risk
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Risk for stroke may be lower with transdermal versus oral hormone replacement therapy (HRT) in postmenopausal women, according to a new study.
Canadian and German researchers performed a population-based, nested case-control study to determine whether route of HRT administration affected stroke risk in postmenopausal women. Data from approximately 400 general practices in the United Kingdom reporting to the General Practice Research Database were examined. Women who were 50 to 79 years of age between Jan. 1, 1987 and Oct. 31, 2006 were included. HRT exposure was classified as estrogens only, estrogens plus progestogen, progestogen only, and tibolone. Estrogens were further classified by oral or transdermal route of administration and high or low dose. The study's main outcome measures were rate ratio of stroke with current oral and transdermal HRT use versus no use. Results were published online June 4 by BMJ.
Overall, 15,710 stroke cases were matched to 59,958 controls over the study period. One thousand two hundred fourteen cases (7.7%) and 4,124 controls (6.9%) received at least one HRT prescription in the year preceding the index date (i.e., the date of the first recorded stroke). The adjusted rate ratio of stroke associated with current transdermal HRT use was 0.95 (95% CI, 0.75 to 1.20) compared with no use. Patches with low estrogen doses did not increase stroke risk compared with no use, while patches with high estrogen doses did (rate ratio, 0.81 [95% CI, 0.62 to 1.05] vs. 1.89 [95% CI, 1.15 to 3.11]). Stroke rate was higher in current low- and high-dose HRT users than in nonusers (rate ratio, 1.28 [95% CI, 1.15 to 1.42]).
The data used in the study were not validated by chart review, and the authors were unable to distinguish between ischemic and hemorrhagic stroke, among other limitations. However, the authors concluded that transdermal HRT with low doses of estrogen does not appear to increase stroke risk among postmenopausal women.
“Although these results alone do not represent definitive evidence to promote the use of the transdermal route over oral administration of oestrogen replacement therapy, this study should encourage further research on the importance of the route of administration to define the role of transdermal oestrogens in the therapeutic arsenal for the treatment of menopausal symptoms,” the authors wrote.