A University of Hawaii researcher has co-authored a landmark government study that found estrogen-only hormone therapy reduced the risk of heart attack and breast cancer in menopausal women who have had hysterectomies.

The new findings, reported yesterday in the Journal of the American Medical Association, are in stark contrast to an initial study that found estrogen to promote breast cancer and overall higher risks of chronic health conditions.

“The study shows it’s possible for women in the 50s to take estrogen for the short term and have benefits,” said UH John A. Burns School of Medical researcher David Curb, a professor of geriatric medicine who co-authored the study with colleagues in 40 of the nation’s top research centers.

Research, which includes more than 10,000 participants including 3,200 women in Hawaii, showed that women in their 50s who had hysterectomies and took estrogen for six or fewer years were less likely to die of heart attack or breast cancer than women of the same age who didn’t take the hormone supplement. There were increased risks for heart attacks for women with hysterectomies in their 70s, and decreased risk for those in their 60s.

Estrogen is used to relieve menopausal symptoms such as hot flashes, sweating and insomnia. Severe symptoms typically last five to six years.

About 15.6 percent of 463,742 women age 18 and older in Hawaii have had a hysterectomy, according to 2009 data by the state Department of Health.

An initial finding in 2004 showed taking estrogen along with progestin, which is thought to protect against uterine cancer, increased risk for heart diseases, with “no substantial benefit for health for taking estrogen,” contrary to the latest report, Curb said.

“It doesn’t mean that an individual doesn’t have to weigh the risk carefully with her own physician because there are a lot of factors that go into weighing risk, but it does provide hope for women who have severe symptoms.”