A new study from Columbia University Mailman School of Public Health has found that breast cancer rates among women under 40 in the U.S. are increasing, but the trends vary depending on location. Researchers suggest that adding geographic information to existing risk factors could help identify young women at higher risk of developing early-onset breast cancer.
This study is the first to use cancer registry data from all 50 states to analyze breast cancer trends based on geography, race, and ethnicity. The findings, published in Cancer Causes & Control, highlight how breast cancer rates differ across states, regions, and urban versus rural areas.
Geographic Differences in Breast Cancer Rates
Between 2001 and 2020, the rate of breast cancer in women aged 25 to 39 increased by more than 0.50% per year in 21 states. However, in other states, the rate remained stable or even decreased.
The Western region of the U.S. saw the fastest-growing increase in breast cancer cases in young women, while the Northeast had the highest overall rates. The Southern states were the only region where breast cancer rates in women under 40 did not rise during this period.
The study found significant differences between states. Wyoming had the lowest early-onset breast cancer rate, with 28.6 cases per 100,000 people, while Connecticut had the highest rate at 41 cases per 100,000. The five states with the highest incidence rates were Maryland, New York, New Jersey, Hawaii, and Connecticut.
Differences by Race and Ethnicity
The study also revealed racial and ethnic disparities in breast cancer rates.
- Non-Hispanic White women were the only racial group with a statistically significant increase in early-onset breast cancer rates in every U.S. region.
- Non-Hispanic Black women had the highest incidence of early-onset breast cancer, regardless of location.
- Hispanic women had the lowest early-onset breast cancer rates across all regions. Their rates ranged from 26 cases per 100,000 in the Midwest to 32.6 per 100,000 in the Northeast.
Why Are Early-Onset Breast Cancer Rates Increasing?
The rising number of breast cancer cases in younger women is concerning, as genetic factors alone cannot explain the trend. Genetic changes take much longer to develop, and women under 40 are generally not included in routine mammogram screenings. This suggests that other factors, such as lifestyle and environmental exposures, could be playing a role.
One possible contributor is alcohol consumption, which is an established risk factor for breast cancer. Alcohol intake varies by state and is influenced by local policies, so it could help explain some of the geographic differences in breast cancer rates.
More research is needed to examine how state-level exposures, including diet, pollution, and lifestyle habits, might contribute to early-onset breast cancer.
The Importance of Understanding Geographic Trends
Dr. Rebecca Kehm, the study’s lead author, emphasized that geographic trends in breast cancer rates could provide new clues about risk factors.
“Until now, we didn’t know whether the increase in breast cancer cases among young women varied across different parts of the country,” she said. “Our findings suggest that certain environmental or lifestyle factors that differ by location could be contributing to the rise in cases.”
Professor Mary Beth Terry, the study’s senior author, added that understanding these trends can help shape future research. “By studying how breast cancer incidence varies across different populations, we can generate new ideas about possible causes and risk factors,” she explained.
Final Thoughts
Breast cancer remains a major health concern, and the fact that cases are increasing among younger women makes early detection and prevention even more important. This study highlights the need to look beyond genetics and consider how environmental, lifestyle, and geographic factors contribute to breast cancer risk.
By incorporating geographic information into risk prediction models, doctors may be able to identify young women at higher risk and provide earlier interventions. Continued research is essential to understanding why breast cancer rates are rising in younger women and what can be done to reduce the risk.
If you care about breast cancer, please read studies about how eating patterns help ward off breast cancer, and soy and plant compounds may prevent breast cancer recurrence.
For more health information, please see recent studies about how your grocery list can help guard against caner, and a simple way to fight aging and cancer.
The research findings can be found in Cancer Causes & Control.
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