Postmenopausal oestrogen treatment and stroke: a prospective study.

STUDY OBJECTIVE: To determine whether post-menopausal oestrogen use affects the risk of dying from stroke. DESIGN: Postal questionnaire survey to elicit details of oestrogen replacement therapy and potential risk modifiers. SETTING: Californian retirement community. PARTICIPANTS: All 22,781 residents of community (white, affluent, well educated) contacted by mail and phone; 13,986 (61%, median age 73) responded, including 8882 women. These formed cohort for mortality follow up, using health department death certification. Only 13 lost to follow up, apparently not deceased, but 34 excluded because no information on oestrogen use. INTERVENTIONS: None. END POINT: Mortality rate from stroke compared in women who did and did not receive oestrogen replacement treatment. MEASUREMENTS AND MAIN RESULTS: Age adjusted mortality rates were computed using internal standard and four age groups. By January 1987 there had been 1019 deaths in the cohort. Twenty out of 4962 women who used oestrogen replacement treatment died from stroke compared with 43 out of 3845 women who did not use oestrogen replacement treatment: relative risk 0.53, 95% confidence interval 0.31 to 0.91. Protection was found in all age groups except the youngest and was unaffected by adjustment for possible confounding factors (hypertension, smoking, alcohol, body mass index, exercise). CONCLUSIONS: Oestrogen replacement treatment protects against death due to stroke.