A study by researchers from Harvard Medical School has found that women should have mammograms performed yearly beginning at age 40, contrary to government recommendations that state the screenings should occur biennially beginning at age 50.

The study, published in the American Cancer Society’s “Cancer” journal on Sept. 9, found that most breast cancer deaths occur in young women who do not receive routine mammogram screening.

“Annual screenings started at 40 increased mortality reduction by almost double,” said Blake Cady, one of the study’s co-authors and a professor emeritus at the Medical School. “A 70 percent mortality reduction equals 22 more lives saved per thousand.”

The study analyzed data on breast cancer diagnoses at the Partners HealthCare hospitals in Boston between 1990 and 1999 and followed each case through 2007. The study’s results showed that 29 percent of women who died from cancer had received prior screening, while the remaining 71 percent had not.

“It’s a very controversial topic,” said Matthew L. Webb ’09, the lead author of the study and a researcher at Massachusetts General Hospital. “Something like one in eight women in their lifetime will get breast cancer.”

The study’s recommendation challenges a report from the United States Preventative Services Task Force, or USPSTF, which suggests women get screened for breast cancer every two years between the ages of 50 and 74.

According to Daniel B. Kopans, one of the study’s co-authors, the USPSTF made their recommendation in spite of evidence that most lives were saved through screenings beginning at age 40 in order to reduce false-positive test results.

“They didn’t know the data and came to faulty conclusions,” said Kopans, who is also a radiology professor at the Medical School.

Though Susan G. Komen for the Cure, a foundation devoted to breast cancer research, said the risk of false positives among women who receive yearly mammograms could cause long-term psychological harm, Cady said yearly mammograms are still critical.

“Paradoxically, if you do mammography every year, the rate of false positive is much less than if you do mammography every two or three years because radiologists can look back a year ago and if they see something consistent, they don’t have to call for extra film,” Cady said.

Kopans said he and his colleagues hope their findings will underscore the importance of mammography.

“My only goal is to provide women and their physicians with accurate information,” Kopans said. “There has been a large amount of misinformation that has been disseminated, and I hope this latest information will dispel the non-science.”