A claim you hear on longevity podcasts

Does exercise lower breast cancer risk and recurrence?

Strong consensus for. Of 10 studies that test it, 9 agree and 1 disagrees.

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Women who want to know how exercise and breast cancer are linked, before and after a diagnosis
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The claim checked: Women who exercise daily get breast cancer less often, and it comes back less often Hear it at 31:13

What do the studies say?

Strong consensus for

Nine of ten studies agree. In pooled cohort studies, the most active women had about 10.3% lower risk than inactive women. Genetic studies, which help rule out other causes, point the same way. One disagrees: in a large study of nurses before menopause, activity made no overall difference. Most studies measured activity over a week, not daily exercise.

Computed from 10 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.

What was said on the podcast?

“We know that women who exercise daily have less risk of getting breast cancer, but if they do get breast cancer, they have there's less cancer growth for those women or less recurrence.”
Elizabeth Boham, a guest on The Doctor's Farmacy · It's Not Bad Luck. This Is What Actually Makes Your Body Vulnerable to Breast Cancer · 31:13 on YouTube
Episode check Bioidentical hormone therapy does not cause breast cancer, the episode says. Four studies conflict on it. 6 claims checked against 72 studies · 7 chapters not checked yet See the whole episode →
Point 1 of 2 Strong consensus for

Women who exercise regularly have a lower risk of getting breast cancer

Agree 9

trial or observed group · 2016 · landmark

“Moderate inverse associations (10–20% reduction in risk) were observed for myeloma (HR=0.83,CI:0.72–0.95), colon cancer (HR=0.84,CI:0.77–0.91), head and neck cancer (HR=0.85,CI:0.78–0.93), rectal cancer (HR=0.87,CI:0.80–0.95), bladder cancer (HR=0.87,CI:0.82–0.92), and breast cancer (HR=0.90,CI:0.87–0.93).”

Association of Leisure-Time Physical Activity With Risk of 26 Types of Cancer in 1.44 Million Adults. JAMA Intern Med
Who: 1.44 million adults (median age 59, range 19-98) pooled from 12 prospective US and European cohorts with self-reported leisure-time physical activity
PMID 27183032

pooled analysis · 2016 · landmark

“Compared with insufficiently active women (reporting less than 600 MET minutes/week of total physical activity), the risk of breast cancer among those in the low active (600-3999 MET minutes), moderately active (4000-7999 MET minutes), and highly active (≥8000 MET minutes) categories was reduced by 3%, 6%, and 14%, respectively.”

Physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events: systematic review and dose-response meta-analysis for the Global Burden of Disease Study 2013. BMJ
Who: Women in prospective cohort studies of total physical activity and breast cancer (part of a 174-study review across five outcomes)
PMID 27510511

other primary study · 2020 · landmark

“In conclusion, we found that genetically elevated levels of accelerometer-measured physical activity were associated with lower risks of breast and colorectal cancer.”

Physical activity and risks of breast and colorectal cancer: a Mendelian randomisation analysis. Nat Commun
Who: European-ancestry women from the Breast Cancer Association Consortium (two-sample Mendelian randomisation using accelerometer-activity GWAS instruments)
PMID 32001714

other primary study · 2020 · landmark

“The strength of association within the recommended activity range varied from 6% to 10% lower for breast cancer (HR at 7.5 MET hours/week [HR 7.5 ], 0.94; HR at 15 MET hours/week [HR 15 ], 0.90) to 11%-17% lower risk for kidney cancer (HR 7.5 , 0.89; HR 15 , 0.83) compared with 0 MET hours/week.”

Amount and Intensity of Leisure-Time Physical Activity and Lower Cancer Risk. J Clin Oncol
Who: 755,459 adults (53% female) with no cancer history, pooled from 5 US, 3 European and 1 Australian prospective cohorts
PMID 31877085

Show 5 more Show fewer

pooled analysis · 2019 · landmark

“Higher physical activity was inversely associated with both pre- and postmenopausal breast cancers, whereas increased sitting time was positively associated with postmenopausal breast cancer.”

World Cancer Research Fund International: Continuous Update Project-systematic literature review and meta-analysis of observational cohort studies on physical activity, sedentary behavior, adiposity, and weight change and breast cancer risk. Cancer Causes Control
Who: Adult women in observational cohort studies of physical activity, sedentary behaviour, adiposity and weight change and pre- and postmenopausal breast cancer
PMID 31471762

other primary study · 2001

“Risk was reduced for exercise only in adolescence (OR = 0.84 (0.70-1.00)); exercise only in adulthood (OR = 0.68 (0.53-0.88)), and was further reduced for exercise in both adolescence and adulthood (OR = 0.47 (0.36-0.62)).”

Lifetime physical activity and breast cancer risk in the Shanghai Breast Cancer Study. Br J Cancer
Who: Women aged 25-64 in urban Shanghai: incident breast cancer cases and age-frequency-matched population controls (population-based case-control study, 1996-1998)
PMID 11286483

other primary study · 2022

“Greater genetically-predicted physical activity was associated with lower risk of invasive breast cancer (OR=0.48;95%CI 0.30–0.78 per-SD [~8 milligravities] in overall activity), with no clearly differential effects by menopausal status, molecular subtype, morphology, stage, or grade (Table 2).”

Physical activity, sedentary time and breast cancer risk: a Mendelian randomisation study. Br J Sports Med
Who: 130,957 European-ancestry women from 76 Breast Cancer Association Consortium studies (two-sample Mendelian randomisation with UK Biobank accelerometer and self-report activity instruments)
PMID 36328784

systematic review · 2023

“Those with low activity levels (600‐3,999 MET‐minutes/week), moderate activity levels (4,000‐7,999 MET‐minutes/week), and high activity levels (≥8,000 MET‐minutes/week) experienced risk reductions of 5.3%, 9.5%, and 10.3%, respectively, compared to women with insufficient activity levels (<600 MET‐minutes /week).”

Physical activity and cancer risk: a dose-response analysis for the Global Burden of Disease Study 2019. Cancer Commun (Lond)
Who: Women in cohort studies of total physical activity and breast cancer (breast studies included only females), within a five-cancer dose-response meta-analysis for GBD 2019
PMID 37743572

other primary study · 2023

“In this prospective cohort study, higher levels of device-measured PA were inversely associated with a lower risk of breast cancer after being adjusted for key confounding factors, including sociodemographic and lifestyle factors and adiposity.”

Associations of Physical Activity With Breast Cancer Risk: Findings From the UK Biobank Prospective Cohort Study. J Phys Act Health
Who: 48,286 women from the UK Biobank cohort with wrist accelerometer data
PMID 36780904

Partly agree 0· none of the studies we read

Disagree 1

other primary study · 2003

“In conclusion, these data among premenopausal women suggest that there is no overall association between activity and risk of breast cancer.”

Physical activity and risk of breast cancer in premenopausal women. Br J Cancer
Who: 110 468 premenopausal US female registered nurses aged 25-42 at baseline (Nurses' Health Study II)
PMID 12942116

Point 2 of 2 Leaning for

Women with breast cancer who exercise have less recurrence

The studies split. Four of ten agree. A pooled analysis of 22 studies found fewer breast cancer events in the most active women after diagnosis. In 1340 women with high-risk breast cancer, those who met activity guidelines had less recurrence. One disagrees: in 1,970 women, activity did not lower recurrence, though it lowered death from any cause. Five are mixed. In 13,302 women from four studies, activity cut death from any cause by 27% but not breast cancer coming back.

Computed from 10 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.

Agree 4

pooled analysis · 2015 · landmark

“The random effects model summary effect size for breast cancer events was 0.79 (0.63–0.98) for when the highest level of self-reported post-diagnosis recreational physical activity was compared to the lowest.”

Physical activity, risk of death and recurrence in breast cancer survivors: A systematic review and meta-analysis of epidemiological studies. Acta Oncol
Who: Women diagnosed with breast cancer in 22 prospective cohort studies of physical activity and death or recurrence
PMID 25752971

other primary study · 2021 · landmark

“The primary finding from these analyses is that patients meeting the minimum PAGAs (yes/no) before diagnosis and at 1-year follow-up experienced statistically significantly reduced hazards of recurrence (HR = 0.59, 95% CI = 0.42 to 0.82) and mortality (HR = 0.51, 95% CI = 0.34 to 0.77); observed associations became stronger at the 2-year follow-up for both recurrence (HR = 0.45, 95% CI = 0.31 to 0.65) and mortality (HR = 0.32, 95% CI = 0.19 to 0.52).”

Physical Activity Before, During, and After Chemotherapy for High-Risk Breast Cancer: Relationships With Survival. J Natl Cancer Inst
Who: 1340 women with high-risk stage I-III breast cancer in the DELCaP study, ancillary to the SWOG S0221 chemotherapy trial
PMID 32239145

other primary study · 2011

“After adjustment for QOL, clinical prognostic factors, and other covariates, exercise during first 36 months post-diagnosis was inversely associated with total mortality and recurrence/disease-specific mortality with hazard ratios of 0.70 (95% confidence interval (CI): 0.56–0.88) and 0.60 (95% CI: 0.47–0.76), respectively.”

Exercise after diagnosis of breast cancer in association with survival. Cancer Prev Res (Phila)
Who: 4,826 Chinese women aged 20-75 with stage I-III breast cancer from the Shanghai Cancer Registry (Shanghai Breast Cancer Survival Study); 4,511 in the recurrence analysis
PMID 21795422

trial or observed group · 2019

“In this analysis of 2042 postmenopausal long-term breast cancer survivors in the MARIE study, we observed that for women who were insufficiently physically active before breast cancer diagnosis but increased their physical activity postdiagnosis to recommended levels, there was a significant 50% reduction in overall mortality, a 46% reduction in breast cancer mortality, and a 42% improvement in recurrence-free survival compared to women who remained insufficiently active.”

Pre- to postdiagnosis leisure-time physical activity and prognosis in postmenopausal breast cancer survivors. Breast Cancer Res
Who: 2,042 postmenopausal German women aged 50-74 at diagnosis with breast cancer (MARIE study), who completed recruitment and 2009 follow-up interviews
PMID 31694687

Partly agree 5

other primary study · 2012

“In conclusion, we observed a 27% reduction in risk of death from any cause among women who adhered to the PA Guidelines 18 to 48 months post-diagnosis, but there was no evidence that this reduction was associated with decreased risk of breast cancer recurrence.”

Meeting the physical activity guidelines and survival after breast cancer: findings from the after breast cancer pooling project. Breast Cancer Res Treat
Who: 13,302 women with stage I-III breast cancer pooled from four prospective cohorts (LACE, NHS, SBCSS, WHEL) in the US and Shanghai, China
PMID 21935600

trial or observed group · 2011

“Neither baseline physical activity nor baseline-to-1-year change in physical activity was significantly associated with additional breast cancer events.”

Physical activity, additional breast cancer events, and mortality among early-stage breast cancer survivors: findings from the WHEL Study. Cancer Causes Control
Who: 2,361 women aged 18-70 treated for stage I (>=1 cm)-IIIA breast cancer in the WHEL Study, alive and recurrence-free at 1 year; ~90% non-Hispanic white, 81% postmenopausal
PMID 21184262

pooled analysis · 2023

“There was no evidence of an association with risk of breast cancer recurrence in linear dose‐response meta‐analysis, but the number of included studies was smaller.”

Postdiagnosis recreational physical activity and breast cancer prognosis: Global Cancer Update Programme (CUP Global) systematic literature review and meta-analysis. Int J Cancer
Who: women diagnosed with primary breast cancer in adulthood, in observational studies of postdiagnosis recreational physical activity (searched PubMed and Embase to 31 October 2021)
PMID 36279903

other primary study · 2016

“In this large, prospective cohort study we found that increasing exercise exposure was not associated with a reduction in the risk of recurrence or breast cancer death in an ‘unselected’ cohort of women with early stage breast cancer.”

Exercise and Prognosis on the Basis of Clinicopathologic and Molecular Features in Early-Stage Breast Cancer: The LACE and Pathways Studies. Cancer Res
Who: 6,211 women with early stage (I with tumor >=1 cm, II, IIIA) breast cancer from the LACE and Pathways cohorts at Kaiser Permanente Northern California and Utah
PMID 27488523

Show 1 more Show fewer

other primary study · 2023

“The evidence on recreational physical activity and risk of breast cancer recurrence was judged as limited and no conclusion could be drawn (6 studies, RR: 0.97, 95% CI: 0.91‐1.05, I 2 : 68%).”

Postdiagnosis body fatness, recreational physical activity, dietary factors and breast cancer prognosis: Global Cancer Update Programme (CUP Global) summary of evidence grading. Int J Cancer
Who: Women diagnosed with first primary breast cancer in adulthood, from RCTs and longitudinal observational studies with at least 100 women each; 20 observational studies for physical activity
PMID 36279885

Disagree 1

trial or observed group · 2009

“These findings do not support a protective effect of physical activity on breast cancer recurrence or mortality but do suggest that regular physical activity is beneficial for breast cancer survivors in terms of total mortality.”

Physical activity and risk of recurrence and mortality in breast cancer survivors: findings from the LACE study. Cancer Epidemiol Biomarkers Prev
Who: 1,970 women aged 18-79 with stage I-IIIa breast cancer diagnosed 1997-2000 (Kaiser Permanente Northern California and Utah registries), treatment completed and recurrence-free at enrollment (LACE study)
PMID 19124485

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