Where your DNA places you among other people, and the studies behind it.
Not tailored to your result, and not medical advice
Take Part in Screening When You Are Invited: Mammographic screening detects breast cancer earlier, when it is more treatable, and national programs set out who is invited and how often. Take up the invitation when it comes, and if you have a strong family history say so, because that can change what is appropriate for you. U.S. Preventive Services Task Force
Limit Alcohol Consumption: Alcohol intake is one of the more consistent modifiable risk factors for breast cancer. A pooled reanalysis of 53 studies estimated that risk rises by about 7% for each additional 10 grams of alcohol (roughly one standard drink) consumed per day, and the association is dose-dependent. Reducing alcohol is a reasonable, evidence-based way to lower risk. British Journal of Cancer
Maintain a Healthy Weight: Excess body weight after menopause is associated with higher risk of estrogen-receptor-positive breast cancer, largely because adipose tissue becomes a major source of estrogen once the ovaries stop producing it. Managing weight through diet and activity is associated with lower risk and may reduce circulating estrogen and inflammatory markers. National Cancer Institute
Exercise Regularly: In observational studies summarized by the NCI, the most physically active women had roughly 12-21% lower breast cancer risk than the least active, with benefit seen before and after menopause. Exercise is thought to act partly by lowering estrogen, insulin, and inflammatory markers. General guidance is 150-300 minutes of moderate activity per week. National Cancer Institute
Consider Genetic Counseling If Family History Is Present: This polygenic score does not test for high-penetrance BRCA1 or BRCA2 mutations, which are a different kind of risk entirely. If you have a first-degree relative with breast cancer, a family pattern of breast or ovarian cancer, or Ashkenazi Jewish ancestry, ask about genetic counseling and clinical BRCA testing. National Cancer Institute
How much of this is genetic?
Genetics explains 31% of why people differ in this trait. The rest is environment, daily habits and chance.
Heritability estimate: Mucci et al. 2016, Cancer Epidemiol Biomark Prev
Background and further reading
Breast cancer is the most commonly diagnosed cancer in women and arises from the uncontrolled growth of breast epithelial cells. In the United States, a woman's average lifetime risk of developing invasive breast cancer is about 13% - roughly a 1 in 8 chance [1]. There are several subtypes (defined largely by estrogen-receptor, progesterone-receptor, and HER2 status) with different treatment responses and prognoses. Risk rises with age, and most cases are diagnosed after age 50. Outcomes have improved markedly: U.S. breast cancer death rates fell by about 44% between 1989 and 2022, driven by earlier detection through screening and better treatment [1].
Genetic Basis: The Nordic Twin Study of Cancer estimates the heritability of breast cancer at about 31% [2]. The genetic contribution falls into two very different categories. A small share of cases (roughly 5-10%) involves rare, high-penetrance mutations - most notably in BRCA1 and BRCA2 - that carry a large individual effect: cumulative breast cancer risk to age 80 is estimated at around 72% for BRCA1 and 69% for BRCA2 carriers [3]. The rest of the heritable risk is polygenic, spread across many common variants of small individual effect identified by GWAS; a large meta-analysis identified 65 new loci, bringing the total to roughly 180 known common-variant regions [4]. From these variants, a 313-SNP polygenic score (PRS313) has been developed [5]. This PRS reflects common-variant polygenic risk and is NOT a substitute for clinical BRCA testing - a low score does not rule out a high-penetrance mutation.
Risk Factors: Alongside genetics, several non-genetic factors are associated with breast cancer risk. Alcohol is consistently linked to higher risk: a pooled reanalysis of 53 studies found risk rose by about 7% for each additional 10 grams of alcohol (roughly one drink) consumed per day [6]. Excess body weight after menopause is associated with elevated risk of estrogen-receptor-positive disease, partly because adipose tissue becomes a major source of estrogen once the ovaries stop producing it [7]. Higher physical activity is associated with roughly 10-20% lower risk in observational studies [7]. Reproductive factors that increase lifetime estrogen exposure - early menarche, late menopause, and not having children - also raise risk. Because these associations come largely from observational data, individual effects vary. Regular mammographic screening does not lower risk but enables earlier detection, when treatment is most effective.
The published research behind your score, and the variants it draws on.
67 published scores from 16 studies
The breast cancer score combines 67 polygenic scores drawn from 16 published studies.
Michailidou K, et al. Association analysis identifies 65 new breast cancer risk loci. Nature (2017)
National Cancer Institute. Physical Activity and Cancer Fact Sheet. National Cancer Institute (2024)
These traits are influenced by some of the same genes and variants as this one
Body Mass Index: A measure of body weight relative to height, used as a proxy for overall adiposity.
Content updated August 2026.
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