A 2025 analysis of the UK Biobank involving 44,316 women has found that high levels of physical activity breast cancer risk dropped by 25.8 percent when measured by accelerometer and by 14.8 percent when measured by self-report. Among women carrying BRCA1 or BRCA2 gene mutations, the reduction reached 50.7 percent. The findings, led by Estee Rebibo and colleagues at Tel Aviv University, are the largest to date linking objectively measured activity to breast cancer prevention in genetically predisposed women.
How the Study Measured Physical Activity Breast Cancer Risk
The research team drew on the UK Biobank, one of the world’s largest prospective health cohorts. They identified 17,409 women who had been diagnosed with breast cancer and 26,907 cancer-free controls. Every participant had genetic data available, including polygenic risk scores and screening for pathogenic variants in cancer susceptibility genes such as BRCA1, BRCA2, TP53 and PALB2.
Physical activity was assessed through two independent instruments. The International Physical Activity Questionnaire captured self-reported exercise in MET-minutes per week, while wrist-worn accelerometers provided objective movement data measured in milli-gravity units. Both measures were divided into tertiles, allowing the researchers to compare the most active women against the least active.
Logistic regression models adjusted for age, body mass index, height and socioeconomic status. The analysis was then stratified by genetic risk category, which is what sets this study apart from earlier work.
The Numbers: 25.8 Percent Risk Reduction in the Full Cohort
Across the entire cohort, women in the highest physical activity tertile showed a 25.8 percent lower odds of breast cancer diagnosis by accelerometer measurement, with a 95 percent confidence interval of 13.5 to 36.4 percent. By self-report, the reduction was 14.8 percent, with a 95 percent confidence interval of 8.4 to 20.8 percent. Both results were statistically significant.
These figures are consistent with earlier meta-analytic evidence. A dose-response analysis for the Global Burden of Disease Study 2019, published in Cancer Communications in 2023, reported that the highest activity levels were associated with roughly a 10 percent lower risk across all cancer types, with breast cancer showing one of the strongest associations. An umbrella review in the European Journal of Epidemiology in 2024 classified physical activity among the few exposures supported by highly suggestive evidence for breast cancer risk reduction.
Women in the highest activity tertile were also younger, had lower body mass index and lower whole-body fat mass. The researchers noted that these metabolic differences may partly explain the protective association, though the statistical models adjusted for body mass index directly.
Genetic Risk Changes the Picture: Up to 50.7 Percent Reduction
The most striking finding emerged when the data were stratified by genetic risk. Among women with a moderate polygenic risk score, high physical activity was associated with a 46.0 percent reduction in breast cancer odds by accelerometer and a 23.7 percent reduction by self-report. Both results were statistically significant, with narrow confidence intervals.
Among confirmed BRCA1 and BRCA2 mutation carriers, self-reported high physical activity was associated with a 50.7 percent reduction in breast cancer odds, with a 95 percent confidence interval of 6.6 to 73.9 percent. The accelerometer-based estimate for this subgroup did not reach statistical significance, but the authors attributed this to the small sample size of only 14 breast cancer cases among BRCA carriers in the accelerometer sub-cohort.
In the lowest polygenic risk tertile, the association was not statistically significant for either measurement method. The authors suggest that when inherited susceptibility is low, the absolute benefit of physical activity may be smaller and harder to detect. In the highest polygenic risk tertile, the association was significant but more modest, at 19.6 percent by accelerometer and 11.2 percent by self-report, suggesting that very strong genetic predisposition may partially attenuate the impact of behavioural factors.
What This Means for Women in Saudi Arabia
Breast cancer is the most commonly diagnosed cancer among women in Saudi Arabia and across the Gulf region. According to the World Health Organization, breast cancer was the most common cancer in women in 164 of 186 countries in 2024, with an estimated 2.4 million new cases and 694,000 deaths globally. Approximately 80 percent of breast cancers develop in women with no known modifiable risk factor other than gender and age, which makes population-level prevention strategies such as physical activity especially important.
The Saudi population carries a distinctive genetic profile. For women navigating sport-related health concerns, research on knee injury prevention in young women offers complementary evidence. Consanguinity rates remain among the highest in the world, which increases the prevalence of recessive conditions and may also influence the distribution of cancer susceptibility variants. A 2024 review in the journal Genes noted that the genetic basis of breast and ovarian cancer in Arab populations includes both well-known BRCA mutations and population-specific variants that are still being characterised.
For Saudi women, these findings offer a concrete, evidence-based message: regular physical activity is one of the few modifiable factors that can meaningfully reduce breast cancer risk, including for women with a family history or known genetic susceptibility. The World Health Organization recommends at least 150 minutes of moderate-intensity aerobic activity per week for adults. In the Saudi context, this could include brisk walking in shaded parks during cooler months, swimming at women-only facilities, or home-based exercise programmes during the summer.
The study also reinforces that physical activity benefits are not limited to women without genetic risk. Even among BRCA carriers, who face lifetime breast cancer risks of 55 to 72 percent, an active lifestyle was associated with a halving of odds. This does not replace clinical surveillance or risk-reducing surgery, but it complements them.
Practical Takeaways
- Aim for at least 150 minutes of moderate-intensity activity per week, as recommended by the WHO. Brisk walking, cycling and swimming all count.
- If you have a family history of breast cancer, physical activity may be even more important. The UK Biobank data showed the largest risk reductions among women with moderate to high genetic risk.
- Objective activity tracking, such as a wrist-worn accelerometer or fitness band, can help you verify that you are reaching the recommended thresholds.
- Physical activity is one component of a broader prevention strategy. Maintain a healthy body weight, limit alcohol intake and attend recommended screening appointments.
- Start gradually if you are currently inactive. Even modest increases in daily movement, such as taking the stairs or walking after dinner, contribute to the overall weekly total.
- Consult your physician about your personal breast cancer risk, especially if you have a family history. Genetic counselling and testing may be appropriate for some women.
Limitations to Keep in Mind
The study has several limitations that the authors acknowledged. The number of BRCA carriers was small, which limits the precision of gene-specific estimates. Accelerometer data were available only in a subset of participants and reflected activity during a single monitoring window, not lifetime patterns. The cohort was predominantly Caucasian, which limits generalisability to other ethnic groups, including Arab populations. Physical activity was assessed only at recruitment, so changes in activity over time were not captured. Residual confounding and reverse causation cannot be entirely excluded.
Nonetheless, the combination of objective and subjective activity measures, the large sample size and the genetic stratification make this one of the most comprehensive analyses of physical activity and breast cancer risk to date.
Sources
- Rebibo E, Amiel N, Shomron N, Friedman E. “Physical Activity in High-Risk Women reduces Breast Cancer Risk: UK Biobank Study.” Research Square, 2025. doi:10.21203/rs.3.rs-8862660/v1
- World Health Organization. “Breast cancer: Fact sheet.” WHO, 3 July 2026. https://www.who.int/news-room/fact-sheets/detail/breast-cancer
- Diao X, Ling Y, Zeng Y, et al. “Physical activity and cancer risk: a dose-response analysis for the Global Burden of Disease Study 2019.” Cancer Communications 2023;43(11):1229-1243. doi:10.1002/cac2.12488
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