Occupational sedentariness and breast cancer risk

Interaction of sedentary behaviour and educational level in breast cancer risk

OBJECTIVE

This cross-sectional study aims to analyse the relationship between sedentary behaviour and breast cancer (BC) risk from a social perspective.

METHODS

Women aged 45-70 who participated in the Valencia Region Breast Cancer Screening Programme (2018-2019) were included, with a total of 121,359 women analysed, including 506 with cancer and 120,853 without cancer. The response variable was BC (screen-detected) and the main explanatory variable was sedentary behaviour (≤2 / >2-≤3 / >3-≤5 / >5 hours/day, h/d). Nested logistic regression models (M) were estimated: M1: sedentary behaviour adjusted for age and family history of BC; M2: M1 + hormonal/reproductive variables (menopausal status, number of pregnancies, hormone replacement therapy; in addition, months of breastfeeding was added for a subsample of women with one or more live births); M3: M2 + lifestyle variables (body mass index, smoking habits); M4: M3 + socioeconomic variables (educational level, occupation); Final model: M4 + gender variables (childcare responsibilities, family size). Interaction between sedentary behaviour and educational level was analysed in the Final model. Moreover, for the whole sample, postmenopausal women and HR+ BC, the Final model was stratified by educational level.

RESULTS

Sedentary behaviour was associated with an increased risk of BC with a nearly statistically significant effect in the Final model (>2-≤3 h/d: OR = 1.22 (0.93-1.61); >3-≤5 h/d: OR = 1.14 (0.86-1.52); >5: OR = 1.19 (0.89-1.60)). For women with a low educational level, sitting more than 2 h/d was associated with an increased risk of BC in the whole sample (>2-≤3 h/d OR = 1.93 (1.19-3.21); in postmenopausal women (>2-≤3 h/d, OR = 2.12 (1.18-2.96), >5h/d OR = 1.75 (1.01-3.11)) and in HR+ BC (>2-≤3h/d, OR = 2.15 (1.22-3.99)). Similar results were observed for women with one or more live births. Conclusions Sitting >2 h/d is associated with BC risk in women with low educational level, especially in postmenopausal women and those with live births.

Seven-plus hours of daily sedentary time and the subsequent risk of breast cancer: Japan Multi-Institutional Collaborative Cohort Study

This study aimed to investigate the association between daily sedentary time and the risk of breast cancer (BC) in a large Japanese population. The participants were 36,023 women aged 35-69 years from the Japan Multi-Institutional Collaborative Cohort Study. Cox proportional hazards analysis was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for BC incidence in relation to time spent sedentarily (categorical variables: <7 and ≥7 hours/day [h/d]). Additionally, the associations of BC incidence to the joint effect of sedentary time with each component of physical activity, such as leisure-time metabolic equivalents (METs), frequency of leisure-time physical activity, and daily walking time, were examined. During 315,189 person-years of follow-up, 554 incident cases of BC were identified. When compared to participants who spent <7 h/d sedentary, those who spent ≥7 h/d sedentary have a significantly higher risk of BC (HR, 1.36; 95% CI, 1.07-1.71). The corresponding HRs among participants who spent ≥7 h/d sedentary with more physical activity, such as ≥1 h/d for leisure-time METs, ≥3 days/week of leisure-time physical activity, and ≥1 h/d of daily walking were 1.58 (95% CI, 1.11-2.25), 1.77 (95% CI, 1.20-2.61), and 1.42 (95% CI, 1.10-1.83), respectively, compared with those who spent <7 h/d sedentary. This study found that spending ≥7 h/d of sedentary time is associated with the risk of BC. Neither leisure-time physical activity nor walking had a BC-preventive effect in those with ≥7 h/d of sedentary time.

The Role of miRNAs in the Prognosis of Triple-Negative Breast Cancer: A Systematic Review and Meta-Analysis

Breast cancer is one of the most common malignancies among women around the world. The basal or triple-negative subtype (TNBC) is a heterogeneous group of tumors, characterized by its aggressive and metastatic nature, with low survival and worse prognosis. Research on genetic biomarkers, such as microRNAs (miRs) in TNBC, demonstrate their relevance in the prognosis of the disease. Therefore, the objective of this research was to verify the role of miRs in the prognosis of TNBC. A search was carried out in the PubMed (MEDLINE), Web of Science, and Scopus databases, with articles in the English language from 2010 to 2022. Only articles that analyzed the role of miRNAs in the prognosis of TNBC and that met the criteria of the MOOSE method were included. For the preparation and planning of this systematic review, a PRISMA checklist and the MOOSE method were used. The Newcastle-Ottawa Scale was used to analyze the quality of the included studies. The excluded criteria considered were: (1) studies that presented duplication in the databases; (2) reviews of the literature, clinical case reports, meta-analyses, conference abstracts, letters to the editor, theses, dissertations, and book chapters; (3) studies that stratified only women diagnosed with other subtypes of breast cancer subtypes; (4) experiments without a control or comparison group. After the bibliographic survey of the 2.274 articles found, 43 articles met the inclusion criteria, totaling 5421 patients with TNBC analyzed for this review. Six miRs (miR-155, miR-21, miR-27a/b/, miR-374a/b, miR-30a/c/e, and miR-301a) were included in the meta-analysis. A low expression of miR-155 was associated with reduced overall survival (OS) (HR: 0.68, 95% CI: 0.58-0.81). A high expression of miR-21 was a predictor of OS reduction (HR: 2.56; 95% CI: 1.49-4.40). In addition, high levels of miR-27a/b and miR-301a/b were associated with lower OS, while the decreased expression levels of miR-30 and miR-374a/b were associated with worse relapse-free survival (RFS) and shorter disease-free survival (DFS), respectively. The present study revealed that miRs play essential roles in the development of metastases, in addition to acting as suppressors of the disease, thus improving the prognosis of TNBC. However, the clinical application of these findings has not yet been investigated.

Multivariate analysis of independent roles of socioeconomic status, occupational physical activity, reproductive factors, and postmenopausal hormonal therapy in risk of breast cancer

PURPOSE

This case-control study assesses the independent roles of reproductive history, postmenopausal hormonal therapy (HT), socioeconomic status (SES), and occupational physical activity on the risk of breast cancer (BC).

METHODS

Odds ratios (OR) were estimated from conditional logistic multivariate regression model in a data set of 19,253 Finnish women diagnosed with BC between 1994 and 2013 and 96,265 age-matched population controls.

RESULTS

Both pre- and postmenopausal white-collar workers had significantly increased risk of ductal and lobular BC as compared to manual workers. Moderate occupational physical activity reduced risk of lobular BC by 14%. There was a transient increase in the risk of BC observed after each birth followed by a protective effect starting some years after the delivery. As the number of children increased, the short-term excess risk was lower and protective effect was observed earlier. Continuous estrogen-progestin therapy (EPT) significantly increased the risk of both ductal and lobular BC and the magnitude of risk was directly proportional to duration of use (OR for 5+ years of use 2.26, 95% confidence interval 2.12-2.42). Monthly EPT for 5+ years increased the risk (OR 1.32, 95% CI 1.20-1.45). Users of estradiol plus levonorgestrel intrauterine system devices showed ORs of 1.56 (95% CI 1.45-1.69) and 2.18 (95% CI 1.81-2.64) for ductal and lobular BC, respectively.

CONCLUSION

This study concludes that pregnancy has a dual effect on BC risk, with a transient increase in risk followed by a long-term protective effect. The SES and HT have a large effect on BC risk while occupational physical activity has only a small independent effect.

Modelling the potential health and economic benefits of reducing population sitting time in Australia

Background

Strong evidence indicates that excessive time spent sitting (sedentary behaviour) is detrimentally associated with multiple chronic diseases. Sedentary behaviour is prevalent among adults in Australia and has increased during the COVID-19 pandemic. Estimating the potential health benefits and healthcare cost saving associated with reductions in population sitting time could be useful for the development of public health initiatives.

Methods

A sedentary behaviour model was developed and incorporated into an existing proportional, multi-state, life table Markov model (ACE-Obesity Policy model). This model simulates the 2019 Australian population (age 18 years and above) and estimates the incidence, prevalence and mortality of five diseases associated with sedentary behaviour (type 2 diabetes, stroke, endometrial, breast and colorectal cancer). Key model inputs included population sitting time estimates from the Australian National Health Survey 2014–2015, healthcare cost data from the Australian Institute of Health and Welfare (2015) and relative risk estimates assessed by conducting literature reviews and meta-analyses. Scenario analyses estimated the potential change in disease incidence as a result of changes in population sitting time. This, in turn, resulted in estimated improvements in long term health outcomes (Health-adjusted life years (HALYs)) and healthcare cost-savings.

Results

According to the model, if all Australian adults sat no more than 4 h per day, the total HALYs gained would be approximately 17,211 with health care cost savings of approximately A$185 million over one year. Under a more feasible scenario, where sitting time was reduced in adults who sit 4 or more hours per day by approximately 36 min per person per day (based on the results of the Stand Up Victoria randomised controlled trial), potential HALYs gained were estimated to be 3,670 and healthcare cost saving could reach A$39 million over one year.

Conclusions

Excessive sedentary time results in considerable population health burden in Australia. This paper describes the development of the first Australian sedentary behaviour model that can be used to predict the long term consequences of interventions targeted at reducing sedentary behaviour through reductions in sitting time. These estimates may be used by decision makers when prioritising healthcare resources and investing in preventative public health initiatives.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12966-022-01276-2.

Occupational risk factors and breast cancer in Beijing, China: a hospital-based case-control study

INTRODUCTION

Studies on the association between breast cancer and occupational hazards are limited, especially in China. This is the first study to explore the relationship between breast cancer and occupational hazards in Beijing, China.

DESIGN

A hospital-based case-control study.

SETTING

Eight local hospitals in Beijing, China.

PARTICIPANTS

A total of 973 female participants, comprising 495 cases and 478 controls, were recruited in our study. We identified patients who underwent diagnosis for breast cancer at one of the eight local hospitals in Beijing between 1 January 2015 and 31 December 2019; controls were individuals randomly matched from the same hospital where the cases were confirmed.

MAIN OUTCOME AND MEASURE

Least absolute shrinkage and selection operator (LASSO) regression was used to estimate the occupational risk factors associated with breast cancer, including night shift work history and work posture.

RESULTS

In the case group, the breast cancer type was mainly invasive, which accounted for 85.66% of all the breast cancer patients. Five risk factors were included in the final LASSO model, including body mass index (BMI), marital status, menopause, night shift work history and work posture. Furthermore, these risk factors were considered for multivariate logistic regression, and the analyses suggested that the risk of breast cancer was significantly associated with higher BMI (≥28.0 kg/m², OR: 2.85, 95% CI: 1.29 to 6.30); married status: married (OR: 2.67, 95% CI: 1.28 to 5.56) or divorced (OR: 4.51, 95% CI: 1.84 to 11.07); menopause (OR: 6.89, 95% CI: 5.07 to 9.36); night shift work (OR: 1.53, 95% CI: 1.11 to 2.11); and maximum standing or walking, and minimal sitting (OR: 1.80, 95% CI: 1.19 to 2.73).

CONCLUSION

Breast cancer is associated with occupational risk factors. Night shift work, especially in a standing posture, can increase the incidence of breast cancer in women in Beijing, China.

A Cluster-Randomised Crossover Pilot Feasibility Study of a Multicomponent Intervention to Reduce Occupational Sedentary Behaviour in Professional Male Employees

Professional male office employees have been identified as those most at risk of prolonged sedentary time, which is associated with many long-term adverse health conditions. The aim of the study was to assess the acceptability and feasibility of a gender-sensitive multicomponent intervention, guided by the socio-ecological model, to reduce occupational sedentary behaviour by increasing physical activity in professional men. The main elements of the intervention comprised: a Garmin watch with associated web-based platform/smartphone application, an under-desk pedal machine, and management participation and support. A cluster-randomised crossover pilot feasibility trial recruiting professional males was conducted in two workplaces. Mixed methods were used to assess the primary outcomes of recruitment, retention, and acceptability and feasibility of the intervention. Secondary outcomes included objectively measured sedentary behaviour, standing and physical activity. Focus groups were used to explore the acceptability of the intervention in a real-world setting. Twenty-two participants were recruited (mean age 42.9 years (SD 11.0)). Recruitment and retention rates were 73.3% and 95%, respectively. Overall, participants found the intervention acceptable and feasible, and expressed enjoyment of the intervention, however desk set-up issues with the pedal devices were noted. The manual recording of the pedalling bouts was overly burdensome. Preliminary data indicate that the intervention may reduce occupational sedentary behaviour and increase physical activity. This intervention should be further tested in a definitive trial following consideration of the findings of this pilot feasibility trial.

Leisure-time physical activity, sedentary behavior, and risk of breast cancer: Results from the SUN ('Seguimiento Universidad De Navarra') project

Evidence is still limited on the influence of sedentary lifestyles on breast cancer (BC) risk. Also, prospective information on the combined effects of both sedentariness and leisure-time physical activity (LTPA) is scarce. We aimed to assess the association of higher sedentary behavior and LTPA (separately and in combination) with the risk of BC in a middle-aged cohort of university graduates. The SUN Project is a follow-up study initiated in 1999 with recruitment permanently open. Baseline assessments included a validated questionnaire on LTPA and sedentary habits. Subsequently, participants completed biennial follow-up questionnaires. Multivariable adjusted Cox models were used to estimate the hazard ratios (HR) for incident BC according to LTPA, TV-watching, the joint classification of both, and a combined 8-item multidimensional active lifestyle score. We included 10,812 women, with 11.8 years of median follow-up of. Among 115,802 women-years of follow-up, we confirmed 101 incident cases of BC. Women in the highest category of LTPA (>16.5 MET-h/week) showed a significantly lower risk of BC (HR = 0.55; 95% CI: 0.34-0.90) compared to women in the lowest category (≤6 MET/h-week). Women watching >2 h/d of TV sh owed a higher risk (HR = 1.67; 95% CI:1.03-2.72) than those who watched TV <1 h/d. Women in the highest category (6-8 points) of the multidimensional combined 8-item score showed a lower BC risk (HR = 0.35; 95% CI: 0.15-0.79) than those in the lowest category (<2 points) group. There was no significant supra-multiplicative interaction between TV-watching and LTPA. Both low LTPA and TV-watching >2 h/d may substantially increase BC risk, independently of each other.

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 theory-based multicomponent intervention to reduce occupational sedentary behaviour in professional male workers: protocol for a cluster randomised crossover pilot feasibility study

BACKGROUND

Prolonged sitting, a significant risk factor for increased morbidity and mortality, is accumulated mostly in the workplace. There is limited research targeting specific at-risk populations to reduce occupational sedentary behaviour. A recent study found that professional males have the longest workplace sitting times. Current evidence supports the use of multi-level interventions developed using participative approaches. This study's primary aims are to test the viability of a future definitive intervention trial using a randomised pilot study, with secondary aims to explore the acceptability and feasibility of a multicomponent intervention to reduce workplace sitting.

METHODS

Two professional companies in Dublin, Ireland, will take part in a cluster randomised crossover pilot study. Office-based males will be recruited and randomised to the control or the intervention arms. The components of the intervention target multiple levels of influence including individual determinants (via mHealth technology to support behaviour change techniques), the physical work environment (via provision of an under-desk pedal machine), and the organisational structures and culture (via management consultation and recruitment to the study). The outcomes measured are recruitment and retention, minutes spent sedentary, and physical activity behaviours, work engagement, and acceptability and feasibility of the workplace intervention.

DISCUSSION

This study will establish the acceptability and feasibility of a workplace intervention which aims to reduce workplace SB and increase PA. It will identify key methodological and implementation issues that need to be addressed prior to assessing the effectiveness of this intervention in a definitive cluster randomised controlled trial.

Association of job category and occupational activity with breast cancer incidence in Japanese female workers: the JACC study

BACKGROUND

Breast cancer represented the leading cause of cancer deaths among women in Japan. Although physical activity has been reported protective against breast cancer, scientific evidence is limited on the risk of breast cancer according to job category or occupational activity in Japanese. Our objective was to examine the association of job category and occupational activity with breast cancer incidence in Japanese female workers using the data from the Japan Collaborative Cohort (JACC) Study.

METHODS

A prospective cohort study involving 19,041 women aged 40-79 years who have reported their occupational data and followed-up from 1988 to 2009. All variables were assessed by a self-administered questionnaire. Cancer incidence data were obtained from 24 areas of the JACC study through cancer population data registration, or review of hospital records. The Cox proportional hazard models were operated to calculate the hazard ratios (HRs) and corresponding 95% confidence intervals (CIs).

RESULTS

There were 138 incident cases of breast cancer during 13.3 years median follow-up period. Office workers compared with manual workers were at a higher risk of breast cancer after adjusting for reproductive health factors and physical activity indicators; the multivariable HR (95% CI) was 1.65 (1.07-2.55). Also, women who had mainly a sitting position during work compared with those moving during work had the higher risk: the multivariable HR (95%CI) of 1.45 (1.01-2.12). The excess risk of breast cancer was observed for office workers when time spent in walking was < 30 min/ day; HR (95% CI) was 1.11 (1.01-1.23), and for women mainly at a sitting position during work when time spent in walking was 30-59 min or < 30 min/day; HRs (95% CIs) were 1.87 (1.07-3.27) and 1.74 (1.07-2.83), respectively.

CONCLUSION

The job category and occupational activity were associated with risk of breast cancer incidence. A high risk was observed in office workers and in women with a sitting position during work. These observed increased risks were evident in women with less daily walking activity.

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

PURPOSE

The purpose of the present study was to systematically review the complex associations between energy balance-related factors and breast cancer risk, for which previous evidence has suggested different associations in the life course of women and by hormone receptor (HR) status of the tumor.

METHODS

Relevant publications on adulthood physical activity, sedentary behavior, body mass index (BMI), waist and hip circumferences, waist-to-hip ratio, and weight change and pre- and postmenopausal breast cancer risk were identified in PubMed up to 30 April 2017. Random-effects meta-analyses were conducted to summarize the relative risks across studies.

RESULTS

One hundred and twenty-six observational cohort studies comprising over 22,900 premenopausal and 103,000 postmenopausal breast cancer cases were meta-analyzed. Higher physical activity was inversely associated with both pre- and postmenopausal breast cancers, whereas increased sitting time was positively associated with postmenopausal breast cancer. Although higher early adult BMI (ages 18-30 years) was inversely associated with pre- and postmenopausal breast cancers, adult weight gain and greater body adiposity increased breast cancer risk in postmenopausal women, and the increased risk was evident for HR+ but not HR- breast cancers, and among never but not current users of postmenopausal hormones. The evidence was less consistent in premenopausal women. There were no associations with adult weight gain, inverse associations with adult BMI (study baseline) and hip circumference, and non-significant associations with waist circumference and waist-to-hip ratio that were reverted to positive associations on average in studies accounting for BMI. No significant associations were observed for HR-defined premenopausal breast cancers.

CONCLUSION

Better understanding on the impact of these factors on pre- and postmenopausal breast cancers and their subtypes along the life course is needed.

Work and Female Breast Cancer: The State of the Evidence, 2002-2017

The authors undertook a scoping review to assess the literature from 2002 to 2017 on the relationship between occupation and female breast cancer. Case-control, cohort, and meta-analytic studies suggest that women working as flight attendants, in medical professions, some production positions, sales and retail, and scientific technical staff are likely to have elevated risk of breast cancer. In addition, occupational exposures to night-shift work, ionizing radiation, some chemicals, job stress, and sedentary work may increase risk of breast cancer. Occupational physical activity appears to decrease risk. Workplace exposures to passive smoke and occupational exposure to nonionizing radiation do not appear to affect breast cancer risk. Some studies of occupational categories and workplace exposures indicate that risk may be modified by duration of exposure, timing of exposure, dose, hormone-receptor subtypes, and menopausal status at diagnosis. The compelling data from this review reveal a substantial need for further research on occupation and breast cancer.

Physical activity and survival following breast cancer

INTRODUCTION

Physical activity (PA) leads to improved survival in women following the diagnosis of breast cancer, but it is less clear whether PA has equally positive effects regardless of age at diagnosis. The purpose of our study was to evaluate the association between post-diagnosis PA and survival in women aged below or over 55 years at diagnosis.

METHODS

From a prospective population-based cohort of Swedish women, we included 847 women, aged 34-84 years, who were diagnosed with breast cancer from 1992 to 2012. A PA score was calculated based on three different questions regarding self-reported PA. Cox proportional hazard model was used to estimate the association between PA and mortality.

RESULTS

A significant association between PA score and all-cause mortality was observed, in a dose-response manner (p_trend  = 0.01). The mortality was clearly lower in the most active compared to the least active group (hazard ratio 0.29, 95% confidence intervals 0.09-0.90). A subgroup analysis showed that the improved survival was only seen in women over 55 years of age at diagnosis.

CONCLUSION

Physical activity, which is a modifiable lifestyle factor, should be encouraged after breast cancer diagnosis, especially in women with post-menopausal breast cancer.

Modifiable Lifestyle Factors: Opportunities for (Hereditary) Breast Cancer Prevention - a Narrative Review

Increasing rates of obesity, lack of physical activity, sedentary behavior, and frequent alcohol consumption are major lifestyle-related risk factors for breast cancer. In fact, it has been estimated that about one-third of breast cancer cases are attributable to factors women can change. Most research has focused on examining the impact of one single exposure on breast cancer risk while adjusting for other risk modifiers. Capitalizing on big data, major efforts have been made to evaluate the combined impact of well-established lifestyle factors on overall breast cancer risk. At the individual level, data indicate that even simple behavior modifications could have a considerable impact on breast cancer prevention. Moreover, there is emerging new evidence that adopting a healthy lifestyle may be particularly relevant for women with hereditary susceptibility to breast cancer. On the absolute risk scale, studies suggest that the presence of certain risk factors, such as excessive body weight, had a substantially higher impact on breast cancer risk if women had a hereditary predisposition to cancer. The existing body of knowledge gives the medical professionals guidance as to which factors to focus on when counseling patients. However, well-designed randomized controlled trials utilizing objective methods are crucial to providing concrete recommendations.

Future cancer research priorities in the USA: a Lancet Oncology Commission

We are in the midst of a technological revolution that is providing new insights into human biology and cancer. In this era of big data, we are amassing large amounts of information that is transforming how we approach cancer treatment and prevention. Enactment of the Cancer Moonshot within the 21st Century Cures Act in the USA arrived at a propitious moment in the advancement of knowledge, providing nearly US$2 billion of funding for cancer research and precision medicine. In 2016, the Blue Ribbon Panel (BRP) set out a roadmap of recommendations designed to exploit new advances in cancer diagnosis, prevention, and treatment. Those recommendations provided a high-level view of how to accelerate the conversion of new scientific discoveries into effective treatments and prevention for cancer. The US National Cancer Institute is already implementing some of those recommendations. As experts in the priority areas identified by the BRP, we bolster those recommendations to implement this important scientific roadmap. In this Commission, we examine the BRP recommendations in greater detail and expand the discussion to include additional priority areas, including surgical oncology, radiation oncology, imaging, health systems and health disparities, regulation and financing, population science, and oncopolicy. We prioritise areas of research in the USA that we believe would accelerate efforts to benefit patients with cancer. Finally, we hope the recommendations in this report will facilitate new international collaborations to further enhance global efforts in cancer control.

Physical activity, sedentary behaviour, diet, and cancer: an update and emerging new evidence

The lifestyle factors of physical activity, sedentary behaviour, and diet are increasingly being studied for their associations with cancer. Physical activity is inversely associated with and sedentary behaviour is positively (and independently) associated with an increased risk of more than ten types of cancer, including colorectal cancer (and advanced adenomas), endometrial cancers, and breast cancer. The most consistent dietary risk factor for premalignant and invasive breast cancer is alcohol, whether consumed during early or late adult life, even at low levels. Epidemiological studies show that the inclusion of wholegrain, fibre, fruits, and vegetables within diets are associated with reduced cancer risk, with diet during early life (age <8 years) having the strongest apparent association with cancer incidence. However, randomised controlled trials of diet-related factors have not yet shown any conclusive associations between diet and cancer incidence. Obesity is a key contributory factor associated with cancer risk and mortality, including in dose-response associations in endometrial and post-menopausal breast cancer, and in degree and duration of fatty liver disease-related hepatocellular carcinoma. Obesity produces an inflammatory state, characterised by macrophages clustered around enlarged hypertrophied, dead, and dying adipocytes, forming crown-like structures. Increased concentrations of aromatase and interleukin 6 in inflamed breast tissue and an increased number of macrophages, compared with healthy tissue, are also observed in women with normal body mass index, suggesting a metabolic obesity state. Emerging randomised controlled trials of physical activity and dietary factors and mechanistic studies of immunity, inflammation, extracellular matrix mechanics, epigenetic or transcriptional regulation, protein translation, circadian disruption, and interactions of the multibiome with lifestyle factors will be crucial to advance this field.