No doubt you recall the recent brouhaha when the US Preventive Services Task Force shocked America by saying that women in their 40s didn't need mammograms to screen for breast cancer. It claimed that the test's downsides—inconvenience, discomfort, risk for false positives—outweighed its benefits because as many as 1,900 women in their 40s would need to be screened to save one life. At the time, many cancer experts denounced the new guidelines, citing research demonstrating that mammograms reduce breast cancer mortality by at least 15%, regardless of age.

Now, a huge Swedish study provides additional evidence that 40-something women should get mammograms. Today, throughout Sweden, mammography screening is standard for women ages 40 to 74but in the past, individual counties determined whether women ages 40 to 49 should be "invited" to screen for breast cancer. Researchers looked at breast cancer mortality among women in their 40s, comparing death rates in counties that did screening for this group with death rates in counties that did not. Women were followed for 16 years, on average, from the time screening started.

Result: Women who got mammograms in their 40s were 29% less likely to die of breast cancer during the study than women who did not get screened.

Bottom line: This study supports the American Cancer Society and American Congress of Obstetricians and Gynecologists, which recommend annual mammograms starting at age 40.

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