The number of younger women diagnosed with breast cancer has been increasing, a trend that has doctors and researchers working to understand why.
The past 20 years have seen a more than 15% increase in the incidence of breast cancer among women under 50. A particular kind of breast cancer that is driven by the hormone estrogen, known as estrogen receptor-positive (ER+) breast cancer, is largely increasing.
Since this type explains nearly all of the rise in instances among younger women, researchers believe the trend may be related to changes in reproductive patterns, as more women are starting menstruation earlier in life and delaying the onset of their first children.
Estrogen receptor-positive breast cancer, the most prevalent form in all age groups, is particularly noteworthy because of its reliance on estrogen links it to hormone exposure over time.
This suggests that changing in the timing of significant life events, such as puberty and childbirth, may be contributing causes.
Dr. Alexandra Thomas, a medical oncologist at Duke Health, said one possible contributing cause is that many women are now exposed to estrogen for longer periods of time throughout their live. she points out, there is still much to learn about why puberty appears to be occurring sooner, which is a crucial topic of research.
Breast cancer risk may also be influenced by a wide range of other factors, including genetic predisposition, alcohol use, obesity, and certain hormonal contraceptives.
Many other factors, such as obesity, alcohol consumption, genetic predisposition, and certain hormonal contraceptives, could also play a role in breast cancer risk.
Among these factors, early puberty has been gaining particular attention for its connection to breast cancer risk. Over the years, the average age at which girls begin menstruating has dropped, especially among Black and Asian American populations.
Dr. Adetunji Toriola, a molecular epidemiologist at Washington University’s Siteman Cancer Center, mentions that early research indicates reproductive factors have a clear connection to breast cancer risk.
Historically, early onset of puberty has been known to correlate with a higher risk of developing breast cancer later in life. However, less is known about how it may affect the age at which women are diagnosed.
A study published in JAMA Network Open examined changes over time in the age of first menstruation among American women. It found that women born between 1950 and 1969 had their first period at an average age of 12.5 years, with fewer than 9% experiencing menarche (the medical term for a girl’s first menstrual period) before age 11, which is considered early. Only 0.6% of these women had their first period before age 9, classified as “very early.”
