Breast Cancer Is Rising in Young People: 4 Possible Reasons Why

It was a rainy March day in Texas when Stephanie Hargis received the call. Her 2-year-old daughter sat in the living room, mesmerized by the fire trucks across the street putting out a small fire, and her husband worked quietly in the other room. “We got your results back from the biopsy. Could you come into the office?” she heard on the other line. Her heart sank. The lump she’d felt under her breast a month earlier wasn’t a swollen lymph node. Hargis, just 25 at the time, would soon be diagnosed with stage II triple negative invasive ductal carcinoma. 

“I knew that you didn’t have to be a certain age to get cancer, but what are the odds? I don’t have any family history, I’m pretty young,” Hargis says. Hargis isn’t alone in this. Cancer, once a disease tied to older age, is on the rise for young people across the world and breast cancer is no exception. 

About 15 years ago, researchers started noticing an alarming trend: more young people were being diagnosed with breast cancer. In the early 2000s and 2010s, breast cancer was rising at about 0.24% per year in women under 50. Now, breast cancer in younger women is rising at double the rate of older women, at about 1.4% per year. Young Hispanic, Asian American, and Pacific Islander people are experiencing even higher rates of breast cancer. 

To understand this rise, experts are untangling a mix of factors that may be making younger people more susceptible to breast cancer:  

Research shows that the longer a person is exposed to the hormones estrogen and progesterone, the more their breast cancer risk increases. This exposure is directly linked to the number of menstrual cycles a person goes through in their lifetime, which has slowly been increasing over the last several decades. 

People born in the U.S. in the 1950s and 1960s on average got their first period when they were 12.5 years old. Younger generations now get their first period about six months earlier, one study found. More young girls are getting their period before the age of nine now too. The trend is greater among Black, Hispanic, Asian, and mixed-race people, and those in families with lower incomes. 

Childhood obesity may be one reason why people are getting periods earlier. Fat cells interact with hormones that kickstart puberty. Another reason may be changes in the environment. Factors like exposure to chemicals from plastics or cosmetics that disrupt hormones may also contribute to early puberty. 

People are also entering menopause later in life. Over the past six decades, the average age people enter natural menopause has increased by 1.5 years. With earlier first periods and later menopause, people have a longer reproductive life span, which increases breast cancer risk.  

Although there are some breast cancer risks connected to having a child, generally speaking, giving birth and breastfeeding are protective against breast cancer in the long run. There are two ways that pregnancy helps to protect against breast cancer: It reduces how many menstrual cycles a person has in their lifetime and allows breast cells to fully develop.  

Prior to pregnancy, breast cells aren’t fully developed and are more likely to respond to estrogen or chemicals that mimic estrogen. This may increase the risk of developing estrogen receptor-positive breast cancer, which relies on estrogen to grow and divide. Pregnancy and breastfeeding change breast cells and tissue, making breasts less vulnerable to cancer. 

Family planning trends are also changing. The U.S. fertility rate has been decreasing since the late 2010s and hit an all-time low in 2023. People are also choosing to have kids later in life. In 2000, people usually gave birth to their first child when they were 24.9 years old. That increased to 27.5 years of age as of 2023.  As more people are choosing to have kids later in life or not at all, their breast cells stay undeveloped for longer, increasing their risk of breast cancer. 

“We're seeing that it's mostly estrogen receptor-positive tumors that are rising in young patients,” says Megan Tesch, MD, MPH, a breast oncologist at Dana-Farber Cancer Institute. “So earlier menstruation, later menopause, delayed childbearing, or not having children at all fit with those findings.”  

How we eat, exercise, sleep, and unwind can all impact our likelihood of developing diseases like breast cancer. In 2019, about one-third of breast cancer cases in the U.S. were linked to behaviors like smoking, lack of exercise, and drinking alcohol. These behaviors may be rising in younger people. 

Alcohol increases the risk of breast cancer. It primes the body for cancer by damaging DNA, disrupting hormone levels, and increasing inflammation. While attitudes are changing around alcohol consumption, since the mid-2000s, binge drinking has been rising among women under 50, especially in those without children and with higher incomes.

Exercising — even for just a few hours a week — reduces the risk of developing breast cancer. But research shows that people are generally less active than they used to be. The Centers for Disease Control and Prevention recommends that people get 2.5 hours of aerobic activity per week and muscle strengthening activities twice a week. In 2020, 80% of women in the U.S. didn’t meet these weekly recommendations.

In the U.S., eating habits have changed drastically over the last century. Americans now eat more saturated fats, red meats, and ultra-processed foods and less fruits and vegetables, whole grains, and fiber. Most U.S. diets don’t meet federal nutrition guidelines. More parts of the world are adopting a similar diet, leading to a rise in obesity. 

In 2022, 1 in 8 people around the world were living with obesity. Obesity doesn’t seem to increase the risk of breast cancer in young people but the foods that young people are eating could make them more vulnerable to cancer.  A 2014 study suggests that people who ate the most animal fat in young adulthood were at a higher risk of early-onset breast cancer than those who ate the least. Still, Tesch cautions, “there’s not enough definitive evidence out there,” on the link between diet and early-onset breast cancer.

“I still see a lot of patients who are young when they’re diagnosed and they’re the healthiest people ever — they eat well and exercise all the time,” Tesch says. “It’s still a bit of a question mark. It makes me wonder about environmental factors.”  

The chemicals we interact with every day may be related to the rise in cancer cases among younger people. Chemicals from plastic, pesticides, and cosmetics “are extremely common and can be found in our air, water, and food,” says Katie O’Brien, PhD, a staff scientist at the National Institute of Environmental Health Sciences. 

Some of these chemicals, like bisphenol A (BPA) and perfluorooctanoic acid (PFOA), increase breast cancer risk by interfering with hormones in our body, like estrogen. 

Exposure to air pollution may also be a risk factor for developing breast cancer because air pollutants can be absorbed into breast tissue and may help mutated breast cells become cancerous. People living in urban areas, near factories, or in places that are prone to wildfires experience higher exposures to air pollution. 

More research is needed. Most studies on the link between environmental exposures and breast cancer are focused on women who have gone through menopause. “We still have a lot to learn about environmental risk factors for breast cancer, which likely do play a role in the increases we are seeing in young women,” O’Brien says. Studies that record “exposures that occur during puberty, adolescence, and early adulthood, especially during women’s reproductive years,” she says, will help scientists pinpoint possible causes of breast cancer in young people.

Tesch emphasizes that it’s important for young people to be aware of the different factors that might increase their risk of breast cancer and do what they can to reduce this risk. “I’m always encouraging people to get genetic testing done to see if they have a predisposition for breast cancer,” she says. Since many young people don’t qualify for yearly screening mammograms, “it’s very important for young people to advocate for themselves when they notice a change in their breasts.”