Contrary to popular belief that estrogen is a risk factor for stroke at all ages, researchers found that the sex hormone actually may prevent strokes in premature or early menopausal women. For the research, published in the journal Menopause, Mayo Clinic scientists analyzed seven other studies to determine how premature or early menopause is associated with stroke.

They found that women who had their ovaries removed before age 50 were more likely to suffer a stroke than women who did not have a bilateral oophorectomy before age 50. But hormone therapy seemed to lower the increased stroke risk for the first group of women, suggesting that a lack of estrogen is linked to the greater risk.

In addition, the age of menopause onset was more important to stroke risk than whether menopause was natural or induced, with earlier onset menopause connected to higher stroke risk.

Study author Walter Rocca said scientists must correct the idea that estrogen is always a problem in the brain. While estrogen can be an issue in older women, the hormone may protect younger women from stroke, he said. Women who experience premature (before age 40) or early menopause (before age 45), whether from natural causes or from ovary removal, should consider taking estrogen up to about age 50 to prevent stroke, Rocca said.

Stroke is the third leading cause of death and the top cause of long-term disability in the U.S. In 2006, more than half of deaths due to stroke were in women, according to the CDC.

Click here to read the Mayo Clinic study.