Adulthood Lifetime Physical Activity and Breast Cancer

Modifiable risk factors in women at high risk of breast cancer: a systematic review

BACKGROUND

Modifiable risk factors (alcohol, smoking, obesity, hormone use, and physical activity) affect a woman's breast cancer (BC) risk. Whether these factors affect BC risk in women with inherited risk (family history, BRCA1/2 mutations, or familial cancer syndrome) remains unclear.

METHODS

This review included studies on modifiable risk factors for BC in women with inherited risk. Pre-determined eligibility criteria were used and relevant data were extracted.

RESULTS

The literature search resulted in 93 eligible studies. For women with family history, most studies indicated that modifiable risk factors had no association with BC and some indicated decreased (physical activity) or increased risk (hormonal contraception (HC)/menopausal hormone therapy (MHT), smoking, alcohol). For women with BRCA mutations, most studies reported no association between modifiable risk factors and BC; however, some observed increased (smoking, MHT/HC, body mass index (BMI)/weight) and decreased risk (alcohol, smoking, MHT/HC, BMI/weight, physical activity). However, measurements varied widely among studies, sample sizes were often small, and a limited number of studies existed.

CONCLUSIONS

An increasing number of women will recognize their underlying inherited BC risk and seek to modify that risk. Due to heterogeneity and limited power of existing studies, further studies are needed to better understand how modifiable risk factors influence BC risk in women with inherited risk.

How the Intensity of Night Shift Work Affects Breast Cancer Risk

Background-In 2019, the IARC concluded that "night shift work is probably carcinogenic to humans (Group 2A), based on limited evidence from human epidemiological studies and sufficient evidence of cancer and strong mechanistic evidence in experimental Animals." The negative health consequences of night shift work may depend on how the night shifts are scheduled. The aim of this study was to investigate how the characteristics of night work affect the risk of developing breast cancer. Methods-A case-control study was conducted in 2015-2019 in the Lodz region. The case group included 494 women with breast cancer, while the control group included 515 healthy women. Results-Night work was found to be the third most important factor regarding breast cancer after a high BMI and a short or no breastfeeding period and before factors such as early menstruation, late menopause, no pregnancy, and smoking. The harmful effects of night work were influenced by its intensity, frequency, rotation, and the number of night shift years worked. Night work increases the breast cancer risk by 2.34 times, and high-intensity night work increases the breast cancer risk by 2.66 times. Conclusions-Appropriate ergonomic recommendations for night shift work for employers should be considered.

Hymenolepis diminuta-based helminth therapy in C3(1)-TAg mice does not alter breast tumor onset or progression

BACKGROUND AND OBJECTIVES

An individual's risk of breast cancer is profoundly affected by evolutionary mismatch. Mismatches in Western society known to increase the risk of breast cancer include a sedentary lifestyle and reproductive factors. Biota alteration, characterized by a loss of biodiversity from the ecosystem of the human body as a result of Western society, is a mismatch known to increase the risk of a variety of inflammation-related diseases, including colitis-associated colon cancer. However, the effect of biota alteration on breast cancer has not been evaluated.

METHODOLOGY

In this study, we utilized the C3(1)-TAg mouse model of breast cancer to evaluate the role of biota alteration in the development of breast cancer. This model has been used to recapitulate the role of exercise and pregnancy in reducing the risk of breast cancer. C3(1)-TAg mice were treated with Hymenolepis diminuta, a benign helminth that has been shown to reverse the effects of biota alteration in animal models.

RESULTS

No effect of the helminth H. diminuta was observed. Neither the latency nor tumor growth was affected by the therapy, and no significant effects on tumor transcriptome were observed based on RNAseq analysis.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that biota alteration, although known to affect a variety of Western-associated diseases, might not be a significant factor in the high rate of breast cancer observed in Western societies.

LAY SUMMARY

An almost complete loss of intestinal worms in high-income countries has led to increases in allergic disorders, autoimmune conditions, and perhaps colon cancer. However, in this study, results using laboratory mice suggest that loss of intestinal worms might not be associated with breast cancer.

Sedentary work and breast cancer risk: A systematic review and meta-analysis

OBJECTIVES

This systematic review and meta-analysis aimed to assess sedentary work's contribution to breast cancer risk quantitatively using thorough research articles.

METHODS

We performed a meta-analysis using a registered protocol in PROSPERO (registration number: CRD42020204629). Literature from PubMed, Embase, and Cochrane involving sedentary work and breast cancer risk was reviewed. We calculated the overall pooled risk ratios (RRs) and 95% CI with a random-effect model from the included studies. Furthermore, we performed stratified analyses by characteristics of studies.

RESULTS

Thirty-one studies (13 cohort studies and 18 case-control studies) were included in the analysis. The overall effect of the pooled analysis was an RR of 1.16 (95% CI 1.08-1.23). The results were 1.20 (95% CI 1.10-1.30) and 1.12 (95% CI 1.02-1.23) for cohort and case-control studies. The effect of sedentary work did not seem to be consistently attenuated by controlling body mass index, menopausal status, or experience of hormone replacement therapy.

CONCLUSION

The results from this meta-analysis suggest that sedentary behavior within the occupational domain was associated with a 15.5% increased risk of breast cancer. It is essential to reduce the sedentary time spent at work and to secure time for leisure-time physical activity among sedentary workers as a primary preventive measure.

A Hunter-Gatherer Exercise Prescription to Optimize Health and Well-Being in the Modern World

There has been considerable innovation and advancement in the field of exercise and physical activity (PA). In regards to the battle against chronic non-communicable disease, however, we believe the model of PA that would prove most salutary is one closely mimicking that of our hunter-gatherer ancestors. For the purpose of longevity, the human body and our genetic makeup have been evolutionarily adapted to respond best to moderate amounts of high-intensity interval training, in conjunction with high amounts of low intensity exercise. Moreover, to optimize resiliency and cardiorespiratory fitness, a hunter-gatherer fitness regimen must include cross training targeted at flexibility, balance and strength. Though not commonly understood, the health benefits from exercise comprise a reverse J-curve. The endurance athletes residing on the furthest reaches of the PA spectrum appear to lose a substantial portion of the exercise-related longevity and cardiovascular benefits due to cardiac overuse injury. Conversely, there is an emerging body of evidence suggesting leisure time exercise done with peers in a natural environment is significantly superior to that training done in solitude. This idea of the "power of play" lends support to the ancestral model of PA whereby humans are evolutionary adapted to be highly social, outdoor creatures capable of a diverse range of PA at varying intensities.

Influence of physical activity at a young age and lifetime physical activity on the risks of 3 obesity-related cancers: systematic review and meta-analysis of observational studies

CONTEXT

Excess weight has been linked to increased risks of 13 types of cancers. Physical activity is a non-nutritional modifiable lifestyle factor that is not only crucial for weight control but is also known to regulate hormones and metabolic pathways that may contribute to carcinogenesis. There is solid evidence that being physically active during middle and late adulthood lowers the risks of 3 obesity-related cancers, namely breast cancer, colon cancer, and endometrial cancer. However, the associations between physical activity at a young age (childhood, adolescence, and young adulthood; age 5 to ≤30 yr) and lifetime physical activity and the risks of breast cancer, colon cancer, and endometrial cancer are less defined.

OBJECTIVE

The present systematic review and meta-analysis of observational studies was performed in accordance with the MOOSE guidelines to determine whether physical activity at a young age and lifetime physical activity may lower the risks of breast cancer, colon cancer, and endometrial cancer.

DATA SOURCES

The PubMed and Web of Science databases were searched for relevant observational studies published from inception to July 2018.

STUDY SELECTION

Observational studies (prospective cohort, case-cohort, nested case-control, historical cohort, and case-control) were considered relevant if they investigated the association between physical activity at a young age or lifetime physical activity and the risks of developing selected cancers.

DATA EXTRACTION

A random-effects meta-analysis was performed to generate the summary relative risk (RR) with 95%CI for the highest vs the lowest category of physical activity of any type.

RESULTS

Eighty publications were included in the present meta-analysis. Higher physical activity at a young age was associated with lower risks of breast cancer (RR 0.81, 95%CI 0.76, 0.87) and colon cancer (RR 0.67, 95%CI 0.50, 0.88). Similarly, lifetime physical activity was inversely associated with the risks of breast cancer (RR 0.79, 95%CI 0.72, 0.86) and colon cancer (RR 0.75, 95%CI 0.69, 0.82). For breast cancer, menopausal status did not appear to modify the observed inverse association. The benefit with respect to endometrial cancer risk reduction was only observed with higher lifetime physical activity (RR 0.77, 95%CI 0.67, 0.88), not with higher physical activity at a young age (RR 0.89, 95%CI 0.73, 1.07).

CONCLUSIONS

Being physically active over a lifetime, starting from early childhood, may lower the risks of developing breast cancer, colon cancer, and endometrial cancer.

Association of physical activity, body mass index and reproductive history with breast cancer by menopausal status in Iranian women

BACKGROUND

The incidence rate of breast cancer (BC) is increasing in low- and middle-income countries (LMICs), including Iran. We investigated the association between BC risk and physical activity (PA), body mass index (BMI), and reproductive history among Iranian women.

METHODS

We conducted a large hospital-based case-control study and compared 958 BC cases with 967 controls at the Cancer Institute of Iran during 2011-2016. We used multiple logistic regression models and adjusted for potential confounders to estimate odds ratios (ORs) and 95% confidence intervals (95%CIs) for the associations between BC and different risk factors, including low physical activity.

RESULTS

Women with high levels of physical activity had a lower risk of BC compared to those who were inactive (OR = 0.55, 95%CI: 0.41, 0.75). In premenopausal women, the association was observed only in normal-weight women (OR = 0.31, 95%CI: 0.13, 0.75), while it was limited to obese women in the postmenopausal group (OR = 0.29, 95%CI: 0.12, 0.66). We found a high risk of postmenopausal BC among overweight (OR = 1.69; 95%CI: 1.01, 2.81) and obese women (OR = 1.9; 95%CI: 1.14, 3.14) compared to women with a normal BMI. We observed an inverse association among postmenopausal women who had between three and five children (OR = 0.31, 95%CI 0.14, 0.64) and more than six children (OR = 0.21, 95%CI 0.12, 0.42) compared to nulliparous women.

CONCLUSIONS

Low levels of physical activity, low parity, and being overweight or obese were major risk factors for BC. For the first time, we report a strong association between physical activity and BC risk in Iranian women.

Occupational sitting time and subsequent risk of cancer: The Japan Public Health Center-based Prospective Study

Although occupational sitting time has been associated with adverse health outcomes and mortality, the association with cancer incidence remains unknown. This study investigated the association between occupational sitting time and risk of total and site‐specific cancer in a Japanese population. We evaluated 33 307 participants aged 50‐79 years who responded to a questionnaire in 2000‐2003 in the Japan Public Health Center‐based Prospective Study and were followed until 2013. Participants were grouped by sitting time at work. Hazard ratio (HR) and 95% confidence interval (CI) of cancer incidence were calculated with adjustment for potential confounders including moderate‐to‐vigorous physical activity. During 10.2 years of follow‐up, 3807 newly diagnosed cases of cancer were identified. Occupational sitting time was marginally associated with total cancer, with multivariable HRs for the ≥7 h/d vs 1 to <3 h/d category of 1.12 (95% CI, 0.99‐1.26; P for trend = .071) in men, but not women. Among findings for cancers at specific sites, long occupational sitting time was associated with increased risk of pancreas cancer, with multivariable HRs for the ≥7 h/d vs 1 to <3 h/d category of 2.25 (95% CI, 1.17‐4.34; P for trend = .021) in men, and lung cancer, with multivariable HRs for the ≥7 h/d vs 1 to <3 h/d category of 2.80 (95% CI, 1.33‐5.90; P for trend = .013) in women. Extended sitting time at work was associated with an increased risk of pancreas cancer in men and lung cancer in women.

An Intervention Tool to Increase Patient-Physician Discussion of Lifestyle Risk Factors for Breast Cancer

Background: Risk assessment and discussion of lifestyle in primary care are crucial elements of breast cancer prevention and risk reduction. Our objective was to evaluate the impact of a breast cancer risk assessment and education tool on patient-physician discussion of behaviors and breast cancer risk. Materials and Methods: We conducted a randomized controlled trial with an ethnically and linguistically diverse sample of women, ages 40-74, from two primary care practices. Intervention participants completed a tablet computer-based Breast Cancer Risk Assessment and Education (BreastCARE) intervention in the waiting room before a scheduled visit. Both patients and physicians received an individualized risk report to discuss during the visit. Control patients underwent usual care. Telephone surveys assessed patient-physician discussion of weight, exercise, and alcohol use 1 week following the visit. Results: Among the 1235 participants, 27.7% (161/580) intervention and 22.3% (146/655) usual-care patients were high risk for breast cancer. Adjusting for clustering by physician, the intervention increased discussions of regular exercise (odds ratios [OR] = 1.94, 1.50-2.51) and weight (OR = 1.56, 1.23-1.96). There was no effect of the intervention on discussion of alcohol. Women with some college education were more likely to discuss their weight than those with high school education or less (OR = 1.75, 1.03-2.96). Similarly, non-English speakers were more likely to discuss their weight compared with English speakers (OR = 2.33, 1.04-5.22). Conclusions: BreastCARE is a feasible risk assessment tool that can successfully promote discussions about modifiable breast cancer risk factors between patients and primary care physicians.

Adult Physical Activity and Breast Cancer Risk in Women with a Family History of Breast Cancer

BACKGROUND

Recreational physical activity has been consistently associated with reduced breast cancer risk. Less is known about how family history of breast cancer affects the association and whether it varies by menopausal status.

METHODS

The Sister Study is a cohort of 50,884 women who had a sister with breast cancer but no prior breast cancer themselves at enrollment. Women reported all recreational sport/exercise activities they participated in over the past 12 months. Hours/week and MET-hours/week of physical activity were considered in association with breast cancer risk. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated with Cox regression. Extent of family history, examined as a modifier, was characterized by a Bayesian score incorporating characteristics of the family structure.

RESULTS

During follow-up (average 8.4 years), 3,023 cases were diagnosed. Higher hours/week (HR_≥7vs<1 = 0.77; 95% CI, 0.66-0.90) and MET-hours/week (HR_quartile4vs1 = 0.75; 95% CI, 0.67-0.85) of physical activity were associated with reduced postmenopausal breast cancer risk. Hours/week and MET-hours/week were associated with suggestively increased premenopausal breast cancer risk (MET-hours/week HR_quartile4vs1 = 1.25; 95% CI, 0.98-1.60). Associations did not vary with extent of family history. However, the increased risk in premenopausal women may be limited to those with stronger family history.

CONCLUSIONS

In women with a family history of breast cancer, physical activity was associated with reduced postmenopausal, but not premenopausal, breast cancer risk and was not modified by extent of family history.

IMPACT

This was the first study to examine the association between physical activity and breast cancer risk in a large population with a family history of breast cancer.

Alcohol, Physical Activity, Smoking, and Breast Cancer Subtypes in a Large, Nested Case-Control Study from the Norwegian Breast Cancer Screening Program

Background: To what extent alcohol, smoking, and physical activity are associated with the various subtypes of breast cancer is not clear. We took advantage of a large population-based screening cohort to determine whether these risk factors also increase the risk of the poor prognosis subtypes.Methods: We conducted a matched case-control study nested within the Norwegian Breast Cancer Screening Program during 2006-2014. A total of 4,402 breast cancer cases with risk factor and receptor data were identified. Five controls were matched to each case on year of birth and year of screening. Conditional logistic regression was used to estimate ORs of breast cancer subtypes adjusted for potential confounders.Results: There were 2,761 luminal A-like, 709 luminal B-like HER2-negative, 367 luminal B-like HER2-positive, 204 HER2-positive, and 361 triple-negative cancers. Current alcohol consumption was associated with breast cancer risk overall [OR 1.26; 95% confidence interval (CI), 1.09-1.45] comparing 6+ glasses a week to never drinkers. However, this risk increase was found only for luminal A-like breast cancer. Smoking 20+ cigarettes a day was associated with an OR of 1.41 (95% CI, 1.06-1.89) overall, with significant trends for luminal A-like and luminal B-like HER2-negative cancer. Current physical activity (4+ hours/week compared with none) was associated with 15% decreased risk of luminal A-like cancer, but not clearly with other subtypes.Conclusions: In this large study, alcohol, smoking, and physical activity were predominantly associated with luminal A-like breast cancer.Impact: Alcohol, smoking, and physical activity were associated with luminal A-like breast cancer subtype. Cancer Epidemiol Biomarkers Prev; 26(12); 1736-44. ©2017 AACR.

Physical activity from menarche to first pregnancy and risk of breast cancer

Breast tissue is particularly susceptible to exposures between menarche and first pregnancy, and a longer interval between these reproductive events is associated with elevated breast cancer risk. Physical activity during this time period may offset breast cancer risk, particularly for those at highest risk with longer menarche-to-first-pregnancy intervals. We used data from 65,576 parous women in the Nurses' Health Study II free of cancer in 1989 (baseline) and recalled their leisure-time physical activity at ages 12-34 in 1997. Current activity was collected at baseline and over follow-up. Relative risks (RRs) were estimated using multivariable Cox proportional hazards regression models. Between 1989 and 2011, 2,069 invasive breast cancer cases were identified. Total recreational activity between menarche and first pregnancy was not significantly associated with the risk of breast cancer. However, physical activity between menarche and first pregnancy was associated with significantly lower breast cancer risk among women in the highest category of a menarche-to first-pregnancy interval (≥20 years; RR for the highest versus the lowest quartile = 0.73, 95% confidence interval = 0.55-0.97; Ptrend  = 0.045; Pinteraction  = 0.048). This was not observed in women with a shorter interval. Physical activity between menarche and first pregnancy was associated with a lower risk of breast cancer among women with at least 20 years between these reproductive events. This may provide a modifiable factor that women can intervene on to mitigate their breast cancer risk associated with a longer interval.

Recreational physical activity and risk of triple negative breast cancer in the California Teachers Study

BACKGROUND

Evidence has accumulated showing that recreational physical activity reduces breast cancer risk. However, it is unclear whether risk reduction pertains to specific receptor-defined subtypes. Moreover, few studies have examined whether changes in the amount of recreational physical activity during adulthood influence breast cancer risk.

METHODS

A total of 108,907 women, ages 22 to 79 years with no history of breast cancer when joining the California Teachers Study in 1995-1996, completed a baseline questionnaire and were eligible for the study. Through 2012, 5882 women were diagnosed with invasive breast cancer. Breast cancer subtypes were defined by the expression status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Multivariable Cox proportional hazards models provided adjusted hazard ratios (HRs) and 95 % confidence intervals (CIs) for breast cancer overall and ER/PR/HER2-defined subtypes associated with long-term (from high school through age 54 or age at cohort entry, whichever was younger) and baseline (during 3 years prior to baseline) recreational physical activity. Among women who also completed a follow-up questionnaire at 10 years after baseline in 2005-2008 (54,686 women, 1406 with invasive breast cancer), risk associated with changes in the amount of recreational physical activity from baseline to the 10-year follow-up (during 3 years prior to the 10-year follow-up) was determined.

RESULTS

Both long-term and baseline strenuous recreational physical activity were inversely associated with risk of invasive breast cancer (P trend ≤0.03). The observed associations were mainly confined to women with triple negative breast cancer (TNBC, ER-/PR-/HER2-, P trend ≤0.02) or luminal A-like subtype (ER+ or PR+ plus HER2-) who were former users of menopausal hormone therapy at baseline (P trend = 0.02, P homogeneity of trends ≤0.03). Moreover, women who consistently engaged in the highest level (≥3.51 h/wk/y) of strenuous recreational physical activity between baseline and 10-year follow-up had the lowest risk of breast cancer (HR = 0.71, 95 % CI = 0.52-0.98) when compared to those who were consistently low (≤0.50 h/wk/y).

CONCLUSIONS

Strenuous recreational physical activity is associated with lower breast cancer risk, especially TNBC. The benefit may be maximized by consistently engaging in high-intensity recreational physical activity during adulthood.

A prospective study of occupational physical activity and breast cancer risk

PURPOSE

Physical activity has been associated with reduced breast cancer risk, but studies of occupational activity have produced inconsistent results. The purpose of this study was to evaluate the relationship between occupational physical activity and breast cancer in a prospective study of women with a family history of breast cancer.

METHODS

We studied breast cancer risk in 47,649 Sister Study participants with an occupational history. Information on occupational activity and breast cancer risk factors was collected during baseline interviews (2004-2009). Physical activity at each job was self-reported and categorized as mostly sitting, sitting and standing equally, mostly standing, and active. Multivariable Cox proportional hazards regression was used to evaluate associations between lifetime occupational activity and incident breast cancer, after adjusting for established risk factors and recreational activity.

RESULTS

During follow-up, a total of 1,798 breast cancer diagnoses were reported. Compared with women who did not spend any time in active jobs, women who spent a high proportion (≥75%) of their working years in active jobs had a reduced risk of breast cancer (HR 0.72; 95% CI 0.52-0.98). Associations were strongest among overweight (HR 0.64; 95% CI 0.42-0.98) and postmenopausal (HR 0.67; 95% CI 0.45-0.98) women.

CONCLUSIONS

Occupational activity was associated with a reduced risk of breast cancer. Occupational activity is a domain of physical activity that should be further examined in studies of postmenopausal breast cancer risk. Additional research is necessary to better understand the mechanisms underlying the relationships between occupational activity, body size, and breast cancer.

Household physical activity and cancer risk: a systematic review and dose-response meta-analysis of epidemiological studies

Controversial results of the association between household physical activity and cancer risk were reported among previous epidemiological studies. We conducted a meta-analysis to investigate the relationship of household physical activity and cancer risk quantitatively, especially in dose-response manner. PubMed, Embase, Web of science and the Cochrane Library were searched for cohort or case-control studies that examined the association between household physical activity and cancer risks. Random-effect models were conducted to estimate the summary relative risks (RRs), nonlinear or linear dose-response meta-analyses were performed to estimate the trend from the correlated log RR estimates across levels of household physical activity quantitatively. Totally, 30 studies including 41 comparisons met the inclusion criteria. Total cancer risks were reduced 16% among the people with highest household physical activity compared to those with lowest household physical activity (RR = 0.84, 95% CI = 0.76-0.93). The dose-response analyses indicated an inverse linear association between household physical activity and cancer risk. The relative risk was 0.98 (95% CI = 0.97-1.00) for per additional 10 MET-hours/week and it was 0.99 (95% CI = 0.98-0.99) for per 1 hour/week increase. These findings provide quantitative data supporting household physical activity is associated with decreased cancer risk in dose-response effect.

Reduced risk of breast cancer associated with recreational physical activity varies by HER2 status

Convincing epidemiologic evidence indicates that physical activity is inversely associated with breast cancer risk. Whether this association varies by the tumor protein expression status of the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), or p53 is unclear. We evaluated the effects of recreational physical activity on risk of invasive breast cancer classified by the four biomarkers, fitting multivariable unconditional logistic regression models to data from 1195 case and 2012 control participants in the population-based Women’s Contraceptive and Reproductive Experiences Study. Self-reported recreational physical activity at different life periods was measured as average annual metabolic equivalents of energy expenditure [MET]-hours per week. Our biomarker-specific analyses showed that lifetime recreational physical activity was negatively associated with the risks of ER-positive (ER+) and of HER2-negative (HER2−) subtypes (both P_trend ≤ 0.04), but not with other subtypes (all P_trend > 0.10). Analyses using combinations of biomarkers indicated that risk of invasive breast cancer varied only by HER2 status. Risk of HER2–breast cancer decreased with increasing number of MET-hours of recreational physical activity in each specific life period examined, although some trend tests were only marginally statistically significant (all P_trend ≤ 0.06). The test for homogeneity of trends (HER2– vs. HER2+ ) reached statistical significance only when evaluating physical activity during the first 10 years after menarche (P_homogeneity = 0.03). Our data suggest that physical activity reduces risk of invasive breast cancers that lack HER2 overexpression, increasing our understanding of the biological mechanisms by which physical activity acts.

Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis

BACKGROUND

The magnitude, consistency, and manner of association between sedentary time and outcomes independent of physical activity remain unclear.

PURPOSE

To quantify the association between sedentary time and hospitalizations, all-cause mortality, cardiovascular disease, diabetes, and cancer in adults independent of physical activity.

DATA SOURCES

English-language studies in MEDLINE, PubMed, EMBASE, CINAHL, Cochrane Library, Web of Knowledge, and Google Scholar databases were searched through August 2014 with hand-searching of in-text citations and no publication date limitations.

STUDY SELECTION

Studies assessing sedentary behavior in adults, adjusted for physical activity and correlated to at least 1 outcome.

DATA EXTRACTION

Two independent reviewers performed data abstraction and quality assessment, and a third reviewer resolved inconsistencies.

DATA SYNTHESIS

Forty-seven articles met our eligibility criteria. Meta-analyses were performed on outcomes for cardiovascular disease and diabetes (14 studies), cancer (14 studies), and all-cause mortality (13 studies). Prospective cohort designs were used in all but 3 studies; sedentary times were quantified using self-report in all but 1 study. Significant hazard ratio (HR) associations were found with all-cause mortality (HR, 1.240 [95% CI, 1.090 to 1.410]), cardiovascular disease mortality (HR, 1.179 [CI, 1.106 to 1.257]), cardiovascular disease incidence (HR, 1.143 [CI, 1.002 to 1.729]), cancer mortality (HR, 1.173 [CI, 1.108 to 1.242]), cancer incidence (HR, 1.130 [CI, 1.053 to 1.213]), and type 2 diabetes incidence (HR, 1.910 [CI, 1.642 to 2.222]). Hazard ratios associated with sedentary time and outcomes were generally more pronounced at lower levels of physical activity than at higher levels.

LIMITATION

There was marked heterogeneity in research designs and the assessment of sedentary time and physical activity.

CONCLUSION

Prolonged sedentary time was independently associated with deleterious health outcomes regardless of physical activity.

PRIMARY FUNDING SOURCE

None.

A randomized, controlled trial to increase discussion of breast cancer in primary care

BACKGROUND

Assessment and discussion of individual risk for breast cancer within the primary care setting are crucial to discussion of risk reduction and timely referral.

METHODS

We conducted a randomized controlled trial of a multiethnic, multilingual sample of women ages 40 to 74 years from two primary care practices (one academic, one safety net) to test a breast cancer risk assessment and education intervention. Patients were randomly assigned to control or intervention group. All patients completed a baseline telephone survey and risk assessment (via telephone for controls, via tablet computer in clinic waiting room before visit for intervention). Intervention (BreastCARE) patients and their physicians received an individualized risk report to discuss during the visit. One-week follow-up telephone surveys with all patients assessed patient-physician discussion of family cancer history, personal breast cancer risk, high-risk clinics, and genetic counseling/testing.

RESULTS

A total of 655 control and 580 intervention women completed the risk assessment and follow-up interview; 25% were high-risk by family history, Gail, or Breast Cancer Surveillance Consortium risk models. BreastCARE increased discussions of family cancer history [OR, 1.54; 95% confidence interval (CI), 1.25-1.91], personal breast cancer risk (OR, 4.15; 95% CI, 3.02-5.70), high-risk clinics (OR, 3.84; 95% CI, 2.13-6.95), and genetic counseling/testing (OR, 2.22; 95% CI, 1.34-3.68). Among high-risk women, all intervention effects were stronger.

CONCLUSIONS

An intervention combining an easy-to-use, quick risk assessment tool with patient-centered risk reports at the point of care can successfully promote discussion of breast cancer risk reduction between patients and primary care physicians, particularly for high-risk women.

IMPACT

Next steps include scaling and dissemination of BreastCARE with integration into electronic medical record systems.

Television viewing and time spent sedentary in relation to cancer risk: a meta-analysis

BACKGROUND

Sedentary behavior is emerging as an independent risk factor for chronic disease and mortality. However, the evidence relating television (TV) viewing and other sedentary behaviors to cancer risk has not been quantitatively summarized.

METHODS

We performed a comprehensive electronic literature search in Cochrane, EMBASE, Medline, and SciSearch databases through February 2014 for published articles investigating sedentary behavior in relation to cancer incidence. Because randomized controlled trials are difficult to perform on this topic, we focused on observational studies that met uniform inclusion criteria. Data were extracted independently by both authors and summarized using random-effects meta-analysis and meta-regression. All statistical tests were two-sided.

RESULTS

Data from 43 observational studies including a total of 68936 cancer cases were analyzed. Comparing the highest vs lowest levels of sedentary time, the relative risks (RRs) for colon cancer were 1.54 (95% confidence interval [CI] = 1.19 to 1.98) for TV viewing time, 1.24 (95% CI = 1.09 to 1.41) for occupational sitting time, and 1.24 (95% CI = 1.03 to 1.50) for total sitting time. For endometrial cancer, the relative risks were 1.66 (95% CI = 1.21 to 2.28) for TV viewing time and 1.32 (95% CI = 1.08 to 1.61) for total sitting time. A positive association with overall sedentary behavior was also noted for lung cancer (RR = 1.21; 95% CI = 1.03 to 1.43). Sedentary behavior was unrelated to cancers of the breast, rectum, ovaries, prostate, stomach, esophagus, testes, renal cell, and non-Hodgkin lymphoma.

CONCLUSIONS

Prolonged TV viewing and time spent in other sedentary pursuits is associated with increased risks of certain types of cancer.

[Relation between physical activity, weight balance and breast cancer]

Many epidemiologic studies, with a good methodology, support the evidence of the positive role of regular physical activity on primary and tertiary prevention of breast cancer on the risk of recurrence and mortality. This relation depends on the level of total energy expenditure by week, which helps balance weight on lifetime, an essential part of benefit. The beneficial effects of physical activity are linked to many interrelated additional mechanisms: in a short-term, contraction of skeletal muscles involves aerobic metabolism which utilizes glucose and amino acids like glutamine, improves insulin sensitivity and lowers plasma insulin; in a long-term, physical activity produces favorable changes in body composition, decreasing body fat and increasing lean mass. That is a key point to reduce the intake of energy substrates stimulating carcinogenesis, to improve insulin sensitivity, to change the ratio of leptin and adiponectin, to enhance cellular immunity and to block cellular pathways of cell proliferation and angiogenesis. Maintaining a healthy weight through regular physical activity well balanced with energy intake is it a goal for prevention of breast cancer.

Intensity of recreational physical activity in different life periods in relation to breast cancer among women in the region of Western Pomerania

Background

Recreational physical activity has been consistently associated with lower breast cancer risk, but there is a need to study the intensity and duration of activity that are critical to reduce the risk. The aim of this study was to examine the influence of moderate and vigorous intensity of recreational physical activity performed at different age periods on breast cancer risk.

Material and methods

The case-control study included 858 women with histological confirmation of invasive breast cancer and 1085 women free of any cancer diagnosis, residents of the region of Western Pomerania, aged 28–79 years. The frequency, duration and intensity of lifetime household, occupational and recreational physical activity, sociodemographic characteristics, reproductive factors, family history of breast cancer, current weight and height, and lifestyle habits were measured using a self-administered questionnaire. Unconditional logistic regression analyses were applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs). The risk estimates were controlled for potential risk factors and lifetime household and occupational activities.

Results

We found a risk reduction for recreational activity done early in life (age periods 14–20, 21–34, 35–50 years), particularly at ages 14–20 and 21–34 years, regardless of intensity. Active women engaging in more than 4.5 hours per week of moderate activity during ages 14–20 years had, on average, a 36% lower risk (OR = 0.64, 95% CI: 0.45–0.89) than women who were never or rarely active. For the women who reported 4.5 hours per week of vigorous activity during this period we found about 64% risk reduction (OR = 0.36, 95% CI: 0.26–0.51). For the period after 50 years of age, recreational activity of moderate or vigorous intensity was not significantly associated with the risk.

Conclusions

Recreational physical activity of moderate or vigorous intensity done during adolescence, early and middle adulthood, particularly at ages 14–20 and 21–34 years, is associated with significantly decreased breast cancer risk.

Accelerometer-based measures of active and sedentary behavior in relation to breast cancer risk

Epidemiologic studies suggest that physical activity reduces breast cancer risk by 20-40 %. However, prior studies have relied on measures of self-report. In a population-based case-control study, we evaluated accelerometer measures of active and sedentary behavior in relation to breast cancer among 996 incident cases and 1,164 controls, residents of Warsaw, Poland (2000-2003), who were asked to wear an accelerometer for 7 days. Accelerometer values were averaged across valid wear days and summarized as overall activity (counts [ct]/min/day); in minutes spent in sedentary behavior (0-99 ct/min); and light (100-759 ct/min) and moderate-to-vigorous (760+ ct/min) activity. Odds ratios (OR) and 95 % confidence intervals (CI) were estimated using unconditional logistic regression. Comparing women in the highest quartile (Q4) of activity to those in the lowest (Q1), time spent in moderate-to-vigorous activity was inversely associated with breast cancer odds after adjustment for known risk factors, sedentary behavior and wear time (OR(Q4vsQ1) 0.39, 95 % CI 0.27-0.56; P-trend < .0001). Sedentary time was positively associated with breast cancer, independent of moderate-to-vigorous activity (OR(Q4vsQ1) 1.81, 95 % CI 1.26-2.60; P-trend = 0.001). Light activity was not associated with breast cancer in multivariable models including both moderate-to-vigorous activity and sedentary behavior. Our findings support an inverse association between accelerometer-based measures of moderate-to-vigorous physical activity and breast cancer while also suggesting potential increases in risk with sedentary time.

Risk and protective factors for breast cancer in Midwest of Brazil

Patterns of physical activity, body composition, and breastfeeding are closely related to health and are influenced by environmental, economic, and social factors. With the increase of sedentary lifestyle and overweight, many chronic diseases have also increased, including cancer. Breast cancer is the most common cancer in women worldwide, and the knowledge of its risk and protective factors is important to the adoption of primary prevention strategies. We aimed to investigate some risk and protective factors for breast cancer among women from Midwest Brazil. It is a case-control study of outpatient basis, carried out with 93 breast cancer cases and 186 controls. Socioeconomic, gynecological, anthropometric, and lifestyle variables were collected, and odds ratios (ORs) values were estimated (significance level, 5%; confidence interval (CI), 95%). Per capita income equal to or lower than 1/2 Brazilian minimum wage (OR = 1.88; CI = 1.06–3.29), residence in rural area (OR = 4.93; CI = 1.65–14.73), and presence of family history of breast cancer (OR = 5.38; CI = 1.46–19.93) are risk factors for breast cancer. In turn, physical activity (past 6 months) (OR = 0.23; CI = 0.10–0.55) and leisure physical activity at 20 years old (OR = 0.13; CI = 0.03–0.54) are protective factors for the disease in women who live in Midwest of Brazil.

[Risk and protective factors for breast cancer: a systematic review]

This review aimed to investigate risk and protective factors for breast cancer and to analyze whether scientific evidence from the World Cancer Research Fund and American Institute for Cancer Research, published in 2007, was confirmed by new research. In May 2010 we reviewed cohort and case-control analytical studies from 2007 to 2010 in the PubMed, LILACS, and SciELO databases. We selected 27 articles (14 case-control and 13 cohort studies). Breastfeeding and physical activity were protective factors against breast cancer, and alcohol consumption was a risk factor. A direct proportional relationship was observed between larger waist circumference, weight throughout adulthood, and height and risk of breast cancer in postmenopausal women. The association between body fat and breast cancer is contradictory in both premenopausal and postmenopausal women. According to the accumulated evidence, breastfeeding and healthy lifestyle are the factors most strongly associated with breast cancer prevention.

Physical activity and breast cancer risk in Chinese women

Background:

The influence of different types and intensities of physical activity on risk for breast cancer is unclear.

Methods:

In a prospective cohort of 73 049 Chinese women (40–70 years), who had worked outside the home, we studied breast cancer risk in relation to specific types of self-reported and work history-related physical activity, including adolescent and adult exercise and household activity and walking and cycling for transportation. Occupational sitting time and physical activity energy expenditure were assigned based on lifetime occupational histories.

Results:

In all, 717 incident breast cancer cases were diagnosed. Breast cancer risk was lower for women in the lowest quartile of average occupational sitting time and in the highest quartile of average occupational energy expenditure (adjusted hazard ratio (HR): 0.81 and 0.73, respectively, P⩽0.05). Adult exercise at or above the recommended level (8 metabolic equivalent (MET) h per week per year) was associated with lower risk (adjusted HR: 0.73, P<0.05) in post-menopausal women. Analysis of joint effects showed that having both an active job and exercise participation did not confer an additional benefit. Other common daily activities were not associated with lower risk.

Interpretation:

These findings suggest that both exercise and occupational activity are associated with lower breast cancer risk, which supports current health promotion campaigns promoting exercise.

Characterizing the impact of 25 years of DCIS treatment

The significant increase in the detection and treatment of ductal carcinoma in situ (DCIS) since the introduction of screening mammography has not been accompanied by the anticipated reduction in invasive breast cancer (IBC) incidence. The prevalence of DCIS requires a reexamination of the population level effects of detecting and treating DCIS. To further our understanding of the possible impact of DCIS diagnosis and treatment on IBC incidence in the U.S., we simulated breast cancer incidence over 25 years under various assumptions regarding the baseline incidence of IBC and the progression of DCIS to IBC. The simulations demonstrate a tradeoff between the expected increased incidence of IBC absent any DCIS detection and treatment and the rate of progression of DCIS to IBC. Our analyses indicate that a high progression of DCIS to IBC implies a significant increase in incidence of IBC over what is observed had we not detected and treated DCIS. Conversely, if we assume that there would not have been a significant increase over and above the observed incidence evident in SEER, then our model indicates that the rate of DCIS progression to clinically significant IBC is low. Given the tradeoff illustrated by our model, we must reevaluate the assumption that DCIS is a short-term obligate precursor of invasive cancer and instead focus on further exploration of the true natural history of DCIS.

Body size, physical activity, and risk of triple-negative and estrogen receptor-positive breast cancer

BACKGROUND

Triple-negative breast cancer, characterized by a lack of hormone receptor and HER2 expression, is associated with a particularly poor prognosis. Focusing on potentially modifiable breast cancer risk factors, we examined the relationship between body size, physical activity, and triple-negative disease risk.

METHODS

Using data from 155,723 women enrolled in the Women's Health Initiative (median follow-up, 7.9 years), we assessed associations between baseline body mass index (BMI), BMI in earlier adulthood, waist and hip circumference, waist-hip ratio, recreational physical activity, and risk of triple-negative (n=307) and estrogen receptor-positive (ER+, n=2,610) breast cancers.

RESULTS

Women in the highest versus lowest BMI quartile had 1.35-fold (95% CI, 0.92-1.99) and 1.39-fold (95% CI, 1.22-1.58) increased risks of triple-negative and ER+ breast cancers, respectively. Waist and hip circumferences were positively associated with risk of ER+ breast cancer (Ptrend=0.01 for both measures) but were not associated with triple-negative breast cancer. Compared with women who reported no recreational physical activity, women in the highest activity tertile had similarly lower risks of triple-negative and ER+ breast cancers (HR=0.77; 95% CI, 0.51-1.13; and HR=0.85; 95% CI, 0.74-0.98, respectively).

CONCLUSIONS

Despite biological and clinical differences, triple-negative and ER+ breast cancers are similarly associated with BMI and recreational physical activity in postmenopausal women. The biological mechanisms underlying these similarities are uncertain and these modest associations require further investigation.

IMPACT

If confirmed, these results suggest potential ways postmenopausal women might modify their risk of both ER+ and triple-negative breast cancers.

Physical activity and breast cancer prevention

Breast cancer is the most commonly diagnosed invasive malignancy and the second leading cause of cancer death in women. This chapter considers epidemiologic evidence regarding the association between physical activity and breast cancer risk from 73 studies conducted around the world. Across these studies there was a 25% average risk reduction amongst physically active women as compared to the least active women. The associations were strongest for recreational activity, for activity sustained over the lifetime or done after menopause, and for activity that is of moderate to vigorous intensity and performed regularly. There is also some evidence for a stronger effect of physical activity amongst postmenopausal women, women who are normal weight, have no family history of breast cancer, and are parous. It is likely that physical activity is associated with decreased breast cancer risk via multiple interrelated biologic pathways that may involve adiposity, sex hormones, insulin resistance, adipokines, and chronic inflammation. Future research should include prospective observational epidemiologic studies relating proposed biomarkers to breast cancer risk and also randomized controlled trials to examine how physical activity influences the proposed biomarkers. Exercise trials will provide more clarity regarding the appropriate type, dose, and timing of activity that relate to breast cancer risk reduction.

Organic fitness: physical activity consistent with our hunter-gatherer heritage

Many of the pervasive health concerns in modern society are the result of diet and lifestyle choices that are at odds with the evolutionary milieu for which we remain genetically adapted. This systematic displacement from a very physically active lifestyle in a natural outdoor environment to a sedentary indoor lifestyle may be at the root of many chronic diseases that are endemic in our culture. A proposed solution is to simulate indigenous human activity patterns in a way that is possible and practical for individuals to achieve. Suggestions for exercise mode, duration, intensity, and frequency are outlined, with a focus on realigning our daily physical activities with the archetype that is encoded within our genome. In a sedentary individual, this type of daily physical activity should help confer the robust vigorous health that enabled our ancestors to survive and thrive as hunter-gatherers in the wild.

Achieving hunter-gatherer fitness in the 21(st) century: back to the future

The systematic displacement from a very physically active lifestyle in our natural outdoor environment to a sedentary, indoor lifestyle is at the root of many of the ubiquitous chronic diseases that are endemic in our culture. The intuitive solution is to simulate the indigenous human activity pattern to the extent that this is possible and practically achievable. Suggestions for exercise mode, duration, intensity, and frequency are outlined with a focus on realigning our daily physical activities with the archetype that is encoded within our genome.

Intensity and timing of physical activity in relation to postmenopausal breast cancer risk: the prospective NIH-AARP diet and health study

BACKGROUND

Despite strong evidence of an inverse association of physical activity with postmenopausal breast cancer risk, whether a certain intensity or time of life of physical activity is most effective for lowering breast cancer risk is not known.

METHODS

In 118,899 postmenopausal women in the prospective NIH-AARP Diet and Health Study, we examined the relations of light and moderate-to-vigorous intensity physical activity during four periods of life ("historical": ages 15-18, 19-29, 35-39 years; "recent": past 10 years) to postmenopausal breast cancer risk. Physical activity was assessed by self-report at baseline, and 4287 incident breast cancers were identified over 6.6 years of follow-up.

RESULTS

In age-adjusted and multivariate Cox regression models, >7 hours/week of moderate-to-vigorous activity during the past 10 years was associated with 16% reduced risk of postmenopausal breast cancer (RR:0.84; 95%CI:0.76,0.93) compared with inactivity. The association remained statistically significant after adjustment for BMI (RR:0.87; 95%CI:0.78,0.96). Neither moderate-to-vigorous activity during other periods of life nor light intensity activity during any period of life was related to breast cancer risk, and associations did not vary by tumor characteristics.

CONCLUSION

A high level of recent, but not historical, physical activity of moderate-to-vigorous intensity is associated with reduced postmenopausal breast cancer risk. More precise recall of recent physical activity than activity in the distant past is one possible explanation for our findings.

Breast clinic and life style study BLLISS

Background

Independent, strong and unequivocal evidence suggests that life style factors such as obesity and lack of physical activity along with certain reproductive choices can increase the risk of breast cancer. There are no studies measuring the effectiveness of guidelines from the Department of Health regarding life style choices made by women presenting to breast clinics. The aim of this audit was to study the prevalence of obesity, physical activity and reproductive factors in women referred to breast clinic.

Patients and methods

All patients attending the Breast clinic as new referrals were invited to complete a life style questionnaire. The data was analysed for prevalence of various risk factors for breast cancer. Three hundred and 73 patients completed the questionnaire.

Results

Final analyses of 373 patients demonstrated that 42% of women performed no exercise and only 24% of patients met Department of Health guideline of 30 minutes of exercise for 5 days a week. Overall 50% of patients were either obese or overweight and 22% of patients had BMI of > 30 kg/m². The median age of menarche was 13 and 18% of women started their period below the age 12. Twenty one percent of women were nulliparous and 14% had their first live birth after the age of 30. Fourteen percent of patients were on the hormone replacement therapy of which 57% have used hormones for more than 5 years. Twenty two percent of women smoked and 9% of women consumed alcohol 5 days a week of which 13% had more than 4 glasses of alcohol in a day.

Conclusion

There is preponderance of high risk life style choices in women attending breast clinic. If these life style options are not modified, there could potentially be a significant rise in the number of breast cancer in West Midlands.

Physical activity and postmenopausal breast cancer risk in the NIH-AARP diet and health study

BACKGROUND

Although physical activity has been associated with reduced breast cancer risk, whether this association varies across breast cancer subtypes or is modified by reproductive and lifestyle factors is unclear.

METHODS

We examined physical activity in relation to postmenopausal breast cancer risk in 182,862 U.S. women in the NIH-AARP Diet and Health Study. Physical activity was assessed by self-report at baseline (1995-1996), and 6,609 incident breast cancers were identified through December 31, 2003. Cox regression was used to estimate the relative risk (RR) and 95% confidence interval (95% CI) of postmenopausal breast cancer overall and by tumor characteristics. Effect modification by select reproductive and lifestyle factors was also explored.

RESULTS

In multivariate models, the most active women experienced a 13% lower breast cancer risk versus inactive women (RR, 0.87; 95% CI, 0.81-0.95). This inverse relation was not modified by tumor stage or histology but was suggestively stronger for estrogen receptor (ER)-negative (RR, 0.75; 95% CI, 0.54-1.04) than ER-positive (RR, 0.97; 95% CI, 0.84-1.12) breast tumors and was suggestively stronger for overweight/obese (RR, 0.86; 95% CI, 0.77-0.96) than lean (RR, 0.95; 95% CI, 0.87-1.05) women. The inverse relation with physical activity was also more pronounced among women who had never used menopausal hormone therapy and those with a positive family history of breast cancer than their respective counterparts.

CONCLUSIONS

Physical activity was associated with reduced postmenopausal breast cancer risk, particular to ER-negative tumors. These results, along with heterogeneity in the physical activity-breast cancer relation for subgroups of menopausal hormone therapy use and adiposity, indicate that physical activity likely influences breast cancer risk via both estrogenic and estrogen-independent mechanisms.

Prospective study of physical activity and risk of postmenopausal breast cancer

INTRODUCTION

To prospectively examine the relation of total, vigorous and non-vigorous physical activity to postmenopausal breast cancer risk.

METHODS

We studied 32,269 women enrolled in the Breast Cancer Detection Demonstration Project Follow-up Study. Usual physical activity (including household, occupational and leisure activities) throughout the previous year was assessed at baseline using a self-administered questionnaire. Postmenopausal breast cancer cases were identified through self-reports, death certificates and linkage to state cancer registries. A Cox proportional hazards regression was used to estimate the relative risk and 95% confidence intervals of postmenopausal breast cancer associated with physical activity.

RESULTS

During 269,792 person-years of follow-up from 1987 to 1998, 1506 new incident cases of postmenopausal breast cancer were ascertained. After adjusting for potential risk factors of breast cancer, a weak inverse association between total physical activity and postmenopausal breast cancer was suggested (relative risk comparing extreme quintiles = 0.87; 95% confidence interval = 0.74 to 1.02; p for trend = 0.21). That relation was almost entirely contributed by vigorous activity (relative risk comparing extreme categories = 0.87; 95% confidence interval = 0.74 to 1.02; p for trend = 0.08). The inverse association with vigorous activity was limited to women who were lean (ie, body mass index <25.0 kg/m2: relative risk = 0.68; 95% confidence interval = 0.54 to 0.85). In contrast, no association with vigorous activity was noted among women who were overweight or obese (ie, body mass index > or = 25.0 kg/m2: relative risk = 1.18; 95% confidence interval = 0.93 to 1.49; p for interaction = 0.008). Non-vigorous activity showed no relation to breast cancer (relative risk comparing extreme quintiles = 1.02; 95% confidence interval = 0.87 to 1.19; p for trend = 0.86). The physical activity and breast cancer relation was not specific to a certain hormone receptor subtype.

CONCLUSIONS

In this cohort of postmenopausal women, breast cancer risk reduction appeared to be limited to vigorous forms of activity; it was apparent among normal weight women but not overweight women, and the relation did not vary by hormone receptor status. Our findings suggest that physical activity acts through underlying biological mechanisms that are independent of body weight control.