A new study from Sweden is stirring fresh debate over whether women in their 40s should get mammograms. It suggests that the breast cancer screening test can lower the risk of dying from the disease by 26 percent or more in this age group.

That’s a bigger benefit than was found by earlier studies, which a year ago led an influential task force of U.S. science advisers to recommend against routine screening before age 50. The panel said the benefits were so small and potential problems from screening so great that the decision should be left to each woman and her doctor.

The new Swedish study appears to be the largest of the 40-49 age group — about 1 million women. Researchers counted breast cancer deaths of women who had been diagnosed in their 40s and died within 16 years.

There were 803 such deaths among women in counties that offered mammogram screening versus 1,238 in counties that didn’t offer it, although the number of women in each group and the amount of time they were followed differed. Researchers did not express the results in terms of death rates, which would have made comparing these groups much easier.

The results translated to a 26 percent lower risk of dying of breast cancer for those offered screening. There was a 29 percent lower risk for women who actually had mammograms, said lead researcher Hakan Jonsson of Umea University in Umea, Sweden.

“It’s just one piece of evidence supporting the fact that screening women in their 40s does save lives,” said the American Cancer Society’s chief medical officer, Dr. Otis Brawley.

But others were unconvinced and stood by the U.S. Preventive Services Task Force. That panel last fall recommended against routine screening for women in their 40s.

“Everybody is confused, but in my opinion, the strength of evidence is robust” for following the panel’s advice, said Dr. Ranit Mishori, a family medicine specialist at Georgetown University.