In November 2009, the U.S. Preventive Services Task Force issued a new recommendation that women under 50 should not have routine screening mammograms unless they are in a high-risk category. The group's previous advice was for women aged 40 and older to get routine screenings every year or two. The new guidelines also recommended against regular breast self-exams.
The task force came to their conclusions based in part on the fact that mammograms produce false-positive results in approximately 10 percent of cases, resulting in unnecessary anxiety, follow-up tests and, in some cases, treatment. The final guidelines as of 2016 recommended biennial screening mammograms for women aged 50 to 74 years. However, many women have important risk factors for breast cancer and should have annual mammograms starting at age 40.

Factors linked to increased risk of breast cancer

The Task Force's recommendations allow exceptions to the age 50 starting point if breast cancer risk is heightened based on a known underlying genetic mutation or a history of radiation to the chest. However, all women with a first degree relative with breast cancer are at increased risk compared to the general population, not just those with family members who have harmful BRCA1 or BRCA2 mutations. In addition, women with a history of benign fibrocystic breast disease, previous breast biopsy, and use of hormone replacement therapy (HRT) (for example, after early hysterectomy) are at increased risk of breast cancer.
Women with dense breasts are more likely to develop breast cancer than those whose breasts consist almost entirely of fat. However, a woman's degree of mammographic density will not be determined until her first mammogram.
There are also some factors relating to prenatal, childhood and adolescent exposures that influence breast cancer risk later in adulthood. For example, high birth weight (and long length at birth) has been linked to increased risk (see our article on the prenatal period and infancy for more information). Early age at menarche (first period), which increases premenopausal cumulative estrogen exposure, also appears to increase subsequent breast cancer risk (see childhood and puberty). Use of tobacco, alcohol or birth control pills starting during the teenage years also disproportionately increases breast cancer risk compared to later use (see teenage years and young adulthood).
In addition, certain occupations have been linked to increased breast cancer risk. These include those with significant exposures to night shift work, ionizing radiation, petroleum-based chemicals such as organic solvents, car and truck exhaust, dyes and inks, pesticides and herbicides. It is difficult to quantify the degree of additional risk conferred by such exposures, however it can be meaningful.
Unfortunately, most cases of breast cancer among women in their 40s are found in those not in a traditional high risk group. For example, one study of women aged 40 to 49 (who were screened with mammograms and found to have breast cancer) reported that invasive breast cancer was diagnosed with equal frequency in women presenting with or without a family history.

Women of color are not well served by the age 50 rule

White women of predominantly European background are more likely to develop breast cancer during their lifetimes than African Americans, Latinas and some Asian American groups. However, when African-American women do develop breast cancer, they tend to be younger (57 year median age at diagnosis compared to 62 to 64 years for whites) and are more likely to have aggressive disease such as triple negative (ER-/PR-/HER2-) or inflammatory breast cancer (IBC). Latinas, as well as women with Indian and Pakistani heritage living in the U.S., are also more likely to be younger at diagnosis (54 to 55 years) and to be diagnosed with triple negative disease. This suggests that starting mammograms at age 40 may be particularly important for many non-white women even if they have no other obvious risk factors.

Overdiagnosis is not solved by restricting the use of mammograms

The underlying problem contributing to overdiagnosis is not that women are having unnecessary mammograms but rather that mammograms need to improve. False positives, false negatives, and problems evaluating mammograms of women with dense breasts are all emblematic of difficulties with regard to mammogram accuracy. More precise screening mammograms and other forms of breast cancer screening are needed.
Below are links to recent studies on this topic. For a more complete list of studies, please click on mammogram.