The study of 130,000 women in two communities in Sweden showed 30 percent fewer women in the screening group died of breast cancer and that this effect persisted year after year.

Now, 29 years after the study began, the researchers found that the number of women saved from breast cancer goes up with each year of screening.

"We've found that the longer we look, the more lives are saved," Professor Stephen Duffy of Queen Mary, University of London, whose study was published in the journal Radiology, said in a statement.

SCREENING CONTROVERSY

New breast screening recommendations issued in 2009 by the U.S. Preventive Services Task Force, an influential advisory group, recommended against routine mammograms for women in their 40s and said women in their 50s should get mammograms every other year instead of every year.

The guidelines contradicted years of messages about the need for routine breast cancer screening starting at age 40, eliciting protests from breast cancer experts and advocacy groups who argued the recommendation for fewer screenings would confuse women and result in more deaths from breast cancer.

The changes were meant to spare women some of the worry and expense of extra tests needed to distinguish between cancer and harmless lumps. But the latest results from the Swedish study show the rate of false positive results was low.