Physical activity

Among 288,802 UK Biobank participants followed for a median of 8.2 years, an abbreviated WCRF/AICR adherence score including physical activity, healthy body weight, diet quality, and alcohol limitation showed a significant inverse association with breast cancer risk. Each 1-point increment was associated with a 10% lower breast cancer risk (HR 0.90; 95% CI 0.87–0.94). The cohort included participants cancer-free at baseline with a mean age of 56.2 years. Cox proportional hazards models adjusted for confounders were used.

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In a prospective cohort of approximately 170,000 Norwegian women from the Norwegian Women and Cancer Study, a higher Healthy Lifestyle Index (HLI) score — constructed from physical activity, BMI, smoking, alcohol intake, and diet — was significantly associated with lower risk of postmenopausal breast cancer. A higher prediagnostic HLI score was also associated with lower all-cause mortality among women diagnosed with breast cancer, with a weak association for breast cancer-specific mortality. Cox proportional hazard models with restricted cubic splines were used for analysis.

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A UK Biobank cohort study evaluated adherence to WCRF/AICR cancer prevention recommendations, with physical activity as a core component of the lifestyle score. In participants who did not report dietary changes over the previous 5 years, greater adherence was significantly associated with reduced breast cancer in situ risk (HR = 0.92, 95% CI = 0.85–0.99). The overall cohort showed a non-significant inverse trend (HR = 0.96, 95% CI = 0.91–1.03). The study confirmed that breast cancer in situ and invasive breast cancer share a similar modifiable risk factor profile.

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An umbrella review of 29 systematic reviews demonstrated that exercising three times per week produced a large effect on cancer-related fatigue reduction (SMD = −0.77, 95% CI −1.04 to −0.05, I² = 0%, P = 0.0001), with zero heterogeneity indicating highly consistent results. Sessions of 30 to 60 minutes showed similarly strong effects (SMD = −0.81, 95% CI −1.15 to −0.47, I² = 42.3%, P = 0.0001). Exercising for over 6 months yielded the largest benefit (SMD = −0.88, 95% CI −1.59 to −0.17, I² = 42.7%, P = 0.0001), suggesting sustained exercise programs provide greater fatigue relief.

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In a pooled analysis of 121,435 women diagnosed with invasive breast cancer across 67 studies (16,890 deaths, 8,554 breast cancer-specific over 10 years), high versus low physical activity was associated with a hazard ratio of 0.43 (95% CI 0.21-0.86) for 10-year all-cause mortality. No evidence of heterogeneous associations by ER status or intrinsic-like subtype was observed (P adj > 0.30), indicating the benefit applied across all breast cancer subtypes examined.

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In a prospective cohort of 96,869 Norwegian women followed from 1996-2004, each one-point increment on the Healthy Lifestyle Index (HLI), which includes physical activity as a component, was associated with a 3% lower risk of postmenopausal breast cancer (HR 0.97, 95% CI: 0.96–0.98). The HLI scored physical activity from 0 to 4 points within a total 0-20 scale. A nonlinear inverse association was observed between HLI score and breast cancer incidence, suggesting benefits may plateau at higher activity levels.

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The SUN prospective cohort study followed 10,930 Spanish female university graduates initially free of breast cancer. Physical activity was one of eight WCRF/AICR compliance score items. Post-menopausal women with highest overall compliance (>5 points) versus lowest (≤3 points) demonstrated a hazard ratio of 0.27 (95% CI: 0.08-0.93) for breast cancer after multivariable adjustment, indicating 73% lower risk. The inverse association reflected the combined effects of physical activity alongside nutritional components.

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This case-control study at the Mohammed VI Centre in Casablanca found that being very active in childhood, peri-menopause, and post-menopause appears to be a protective factor against breast cancer occurrence. The data showed that physical activity participation decreases with age — women are more active in childhood and adolescence but become only moderately active in post-menopause. Physical inactivity was explicitly identified as a behavioral factor that increases breast cancer risk. The study concluded that maintaining activity across life stages is a modifiable protective behavior.

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In this systematic review of multiple epidemiological studies, physical activity and cardiorespiratory fitness demonstrated an inverse association with breast cancer incidence in females. The protective effect operated independently of body mass, though no statistically significant interaction was found between body fatness and physical activity on breast cancer outcomes. The review concluded that high physical activity levels do not eliminate obesity-conferred breast cancer risk, but physical activity provides independent cancer risk reduction. Both maintaining a healthy body weight and achieving recommended physical activity levels are needed to optimally reduce breast cancer risk.

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The EPIGEICAM multicenter matched case-control study of 973 case-control pairs used physical activity as an explanatory variable in a linear regression model to predict individual caloric needs. The study concluded that moderate caloric restriction combined with regular physical activity could serve as an effective breast cancer prevention strategy, supported by the strong dose-response relationship between excess caloric intake and breast cancer risk across all pathologic subtypes (p-trend < 0.001 for hormone receptor positive; p-trend = 0.015 for HER2+; 13% risk increase per 20% caloric excess for HR+ and HER2+ tumours).

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Among 344 breast cancer survivors and 347 controls aged 60-98 followed over 24 months, baseline frailty was significantly associated with lower attention, processing speed, and executive function (APE) scores (P < .001) and greater self-reported cognitive decline (P < .001). Increasing age was also associated with lower baseline scores on all cognitive measures (P < .001). These findings indicate that modifiable aging-related phenotypes like frailty compound the cognitive effects of cancer treatment, suggesting that interventions targeting frailty may help preserve cognitive function in older breast cancer survivors.

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In this two-arm RCT of 78 participants with a family history of breast or colorectal cancer and BMI ≥25 kg/m², the 12-week lifestyle intervention produced favourable increases in physical activity. Accelerometer-measured data were collected at baseline (84% compliance) and follow-up (54% compliance). The intervention combined one face-to-face session, four telephone consultations, web-based support, and behavioral change techniques including motivational interviewing and implementation intentions, with 76% participant retention.

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In a population-based cohort of 1,254 women with first primary breast cancer followed for approximately 15 years, 486 deaths occurred (186 breast cancer-related). Physically active women with methylated tumor promoters showed significantly lower all-cause mortality: APC methylation (HR 0.60, 95% CI 0.40–0.80), CCND2 methylation (HR 0.56, 95% CI 0.32–0.99), HIN methylation (HR 0.55, 95% CI 0.38–0.80), and TWIST1 methylation (HR 0.28, 95% CI 0.14–0.56). All interactions were statistically significant (p < 0.05). No survival benefit from physical activity was observed among women with unmethylated tumors for these genes. Average lifetime recreational physical activity was assessed from menarche to diagnosis.

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The joint position statement from seven international societies (IOF, CABS, ECTS, IEG, ESCEO, IMS, SIOG) includes exercise as a universal recommendation for all patients initiating aromatase inhibitor treatment. The systematic literature review identified exercise alongside calcium and vitamin D supplementation as foundational measures for fracture risk management. This recommendation applies to all patients regardless of baseline bone mineral density, with the algorithm specifying that even patients with T-scores above -1.5 and no additional risk factors should receive exercise guidance as part of standard care.

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In a randomized controlled trial of 80 post-adjuvant therapy invasive breast cancer patients (mean age 53.6 ± 9.4 years), a 6-month home-based physical activity intervention with face-to-face and telephone counseling was compared to usual care (n=40 per group). The intervention group showed significantly greater increases in total PA (578.5 MET-min/wk, p=.024), leisure PA (382.2 MET-min/wk, p=.010), and vigorous PA (264.1 MET-min/wk, p=.007). Body mass decreased by 1.6 kg (p=.040) and BMI by 0.6 kg/m² (p=.020) compared to usual care. FACT-Breast quality of life improved (between-group difference 5.1, p=.024), functional wellbeing improved (1.9, p=.025), and breast cancer subscale improved (2.8, p=.007). Total cholesterol decreased by 0.38 mmol/L (p=.001) and LDL-C by 0.3 mmol/L (p=.023).

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In a case-control study of 260 women diagnosed with breast cancer and 260 matched controls in Kerman, a statistically significant difference was found in recreation patterns between the two groups (p < 0.05, chi-square test). Controls engaged in more recreational activities compared to breast cancer patients, supporting the association between active leisure-time behaviors and reduced breast cancer risk.

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Meta-analysis of 38 independent prospective studies (116,304 breast cancer cases, published 1987-2014) using random-effects models. Highest versus lowest physical activity level yielded a summary relative risk (SRR) of 0.88 (95% CI 0.85-0.90) for all breast cancer, 0.89 (95% CI 0.83-0.95) for ER+/PR+ breast cancer, and 0.80 (95% CI 0.69-0.92) for ER-/PR- breast cancer. Dose-response analysis showed risk reductions increased with increasing physical activity without threshold effect. A physically inactive woman engaging in at least 150 minutes per week of vigorous activity would reduce lifetime breast cancer risk by approximately 9%. In women who never used HRT, the SRR was 0.78 (95% CI 0.70-0.87), suggesting the risk reduction may be approximately twice as great compared to the overall population.

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In this 16-week RCT, the mainly exercise group (N=98) lost 5.5 kg total versus 4.9 kg in the diet group (N=97), but achieved significantly greater fat loss (difference −1.4 kg, P<0.001) while maintaining lean mass. The exercise group showed a statistically significantly greater reduction in free testosterone compared to diet alone (TER 0.92, P=0.043), with suggestive differences for androstenedione (TER 0.90, P=0.064) and SHBG (TER 1.05, P=0.070). Greater fitness improvements were also observed in the exercise arm.

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Among 242,918 postmenopausal women in the EPIC cohort with 10.9 years median follow-up, physical activity was one of five HLIS components scored 0-4. A total of 7,756 breast cancer cases were identified. The highest versus second HLIS category showed a 26% reduction in breast cancer risk (adjusted HR = 0.74; 95% CI: 0.66-0.83), with a 3% risk reduction per unit HLIS increase. The association was significant for hormone receptor double positive breast cancer (HR = 0.81, 95% CI: 0.67-0.98) and even stronger for hormone receptor double negative breast cancer (HR = 0.60, 95% CI: 0.40-0.90).

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In a randomized controlled trial of 641 older, overweight, long-term cancer survivors (breast, prostate, and colorectal), telephone session attendance had significant indirect relationships with health outcomes through exercise behavior. Attendance showed positive indirect effects on physical function (β = 0.11, p < 0.05), basic lower extremity function (β = 0.10, p < 0.05), advanced lower extremity function (β = 0.09, p < 0.05), and mental health (β = 0.05, p < 0.05). Exercise behavior during the year-long intervention was a key mediator of these improvements, assessed across 14 time points.

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In a randomized controlled trial of 67 breast cancer patients undergoing adjuvant chemotherapy, participants were assigned to either a scheduled home-based exercise group (n=33, strength training 3x/week plus 30 minutes brisk walking/day) or a control group (n=34, regular physical activity). Cancer-related fatigue increased at chemotherapy completion (Post1) in both groups but returned to baseline at 6-month follow-up (Post2). Physical fitness and activity levels decreased at Post1 but significantly improved at Post2 in both groups. No significant differences were found between the structured exercise and control groups, indicating that generally recommended physical activity levels are sufficient to relieve cancer-related fatigue and restore physical capacity during adjuvant chemotherapy.

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In a New Zealand case-control study including 1093 breast cancer cases and 2118 controls, higher exercise levels were one of eleven healthy lifestyle index factors. Postmenopausal Māori women in the top HLIS tertile had 53% lower odds of breast cancer (OR 0.47, 95% CI 0.23-0.94) versus the bottom tertile. The study was population-based with controls matched by ethnicity and 5-year age bands, using logistic regression stratified by menopausal status.

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This RCT (n=80 enrolled, 65 completed 3-month follow-up) demonstrated significant between-group differences favouring the intervention for both physical activity and sitting time. The 3-month ActWell programme targeted body weight, physical activity, and alcohol intake in women aged 58 ± 5.6 years attending routine breast screening. Retention was 81%, and the programme was rated highly by participants, with 70% stating they would recommend it. The study was conducted at two NHS Scottish Breast Screening Programme sites between June 2013 and January 2014.

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In a randomized controlled trial of 85 overweight women 3–18 months after early-stage breast cancer treatment, a 6-month intervention including three supervised exercise sessions per week plus hypocaloric healthy eating significantly reduced depressive symptoms compared to usual care (adjusted mean difference −3.12, 95% CI −1.03 to −5.26, P = 0.004). The intervention also normalized diurnal salivary cortisol rhythm, with a significant increase in morning cortisol at 6 months (P < 0.04), indicating improved HPA axis regulation. Control group women had higher total leukocyte, neutrophil, and lymphocyte counts (P ≤ 0.05), while NK cell counts (P = 0.46), NK cell cytotoxicity (P = 0.85), and lymphocyte proliferation (P = 0.11) did not differ between groups.

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A case-control study of 472 breast cancer patients and 464 controls in Japanese women found current leisure-time exercise significantly associated with decreased breast cancer risk in multivariate-adjusted logistic regression (p < 0.05). Among carriers of the rs2046210 risk allele (per allele OR = 1.37 [95% CI: 1.11–1.70] for breast cancer), leisure-time exercise was associated with a significantly decreased risk, indicating that physical activity may counteract genetic susceptibility linked to the ESR1 gene region.

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Over 100 international breast cancer experts across clinical, scientific, and healthcare disciplines identified exercise as a critical component of breast cancer prevention. In the consensus statement's top 10 research gaps, gap number 2 specifically calls for understanding how to implement sustainable lifestyle changes including exercise as a chemopreventive strategy. The risk and prevention thematic group, one of 9 expert panels contributing to the analysis, prioritised exercise alongside diet and weight management as actionable interventions with established evidence supporting their role in breast cancer risk reduction.

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Case-control study of 168 Mexican women (84 cases, 84 controls) stratified by age and center across Acapulco and Toluca (March 2009–March 2010). Physical exercise showed a protective effect with OR 0.39 (95% CI 0.18–0.84, p<0.017) in multivariate analysis, indicating a 61% reduction in breast cancer risk among physically active women. Bivariate analysis also supported a protective trend (OR 0.71, 95% CI 0.17–0.62).

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A population-based cohort study of 287 breast cancer patients in South-East Queensland, Australia, assessed physical activity and health-related quality of life (HRQoL) every three months from 6 to 18 months post-surgery. Physical activity was measured using the Behavioral Risk Factor Surveillance System questionnaire and assigned metabolic equivalent task (MET) values. HRQoL was measured using the Functional Assessment of Cancer Therapy-Breast questionnaire (FACTB+4). Active participants showed significantly better HRQoL compared to inactive participants (p<0.05). Age influenced the relationship between physical activity and HRQoL benefits, with results indicating that some groups of women are at greater risk of long-term sedentary behavior and may need targeted intervention approaches.

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A health economic evaluation of the UK population used WHO global burden of disease methodology to calculate mortality and morbidity costs attributable to physical inactivity. Breast cancer was included among five diseases with established population attributable fractions for physical inactivity. Across all five conditions, physical inactivity accounted for 3% of disability adjusted life years lost in the UK in 2002 and an estimated £1.06 billion in direct NHS costs. Only 25% of women were meeting government physical activity recommendations at the time of analysis.

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A case-control study of 257 breast cancer cases and 565 controls assessed lifetime sport activity using metabolic equivalents of energy expenditure (MET)-weighted frequency. Sport-active women had an OR of 0.49 (95% CI: 0.35-0.69) compared to inactive women. Dose-response analysis showed increasing tertiles of sport activity yielded ORs of 1.00 (referent), 0.50 (95% CI: 0.33-0.76), and 0.44 (95% CI: 0.28-0.64), with a significant trend (P-trend = 0.000). The protective effect remained consistent in models stratified by BMI, age at menarche, age at first full-term pregnancy, vegetable and fruit intake, and stress experience. Multivariate logistic regression controlled for confounding, and full assessment of effect modification was performed.

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In a population-based cohort of 4,345 women diagnosed with breast cancer between 1995 and 2008 in the San Francisco Bay Area, with follow-up through 2009, women who were not recreationally physically active had a 22% higher risk of death from any cause compared to the most physically active women. Physical activity was assessed via questionnaire measuring moderate and strenuous recreational activity during the 3 years before diagnosis. Survival was evaluated using multivariable Cox proportional hazards models adjusting for neighborhood and individual-level factors. Lower neighborhood socioeconomic status was independently associated with poorer overall survival (p trend = 0.02).

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