Some women take estrogen hormone therapy to help with the uncomfortable symptoms of menopause and in the hopes that the therapy can protect against cognitive decline, such as dementia and memory loss.
But a new study has bad news about estrogen therapy.
"Women who were taking estrogen only, had an increased risk of developing dementia," Dr. Rapp said.
Dr. Stephen Rapp and colleagues at Wake Forest University School of Medicine and eight other institutions around the U.S.. analyzed data from the women's health initiative memory study.
Their findings appear in the journal of the American Medical Association. They tracked nine years of data on about 3,000 women age 65 and over. Half those women took estrogen alone. Half took placebo, or sugar pill.
"We found about a 50 percent increased risk in the women taking estrogen, compared with the women who were taking placebo," said Rapp.
The researchers say that for every 10,000 women taking estrogen alone, 23 would develop dementia each year, compared to 12 per 10,000 each year for the placebo group, a difference of just 11 per 10,000 per year. So the risk to the individual woman is quite small.
"But when we think about the number of women who are taking estrogen therapy at this time, and that number is in the millions, suddenly the impact of the risk of dementia on estrogen therapy becomes quite meaningful," Rapp said.
These findings mirror last year's women's health initiative memory study findings on estrogen plus progestin.
Dr. Rapp said both studies have the same conclusion.
"Women over 65 should not be taking hormone therapy to protect them from developing dementia or to protect them from memory problems," said Rapp.