The importance of body size versus weight distribution for cancer risk is unclear. We investigated associations between measures of body size and shape and the risk of developing cancer. The study ...population consisted of 26,607 participants from the Alberta's Tomorrow Project cohort. Two main measures of body shape and size were examined: i) body mass index (BMI) and ii) waist circumference (WC). Incident cancers were identified via linkage to the Alberta Cancer Registry. Cox proportional hazards models were used. Males and females classified as obese (BMI ≥ 30 kg /m
) have a 33% and 22% increased risk of all-cancer, respectively, than their normal weight counterparts. Similar all-cancer risk increases are observed for those above sex-specific WC guidelines. Mutual adjustment for WC attenuates the association between BMI and all-cancer risk, especially among females. Central adiposity appears to be a stronger predictor of all-cancer risk than body size.
In July, 2019, the World Health Organization (WHO) commenced work to update the 2010 Global Recommendations on Physical Activity for Health and established a Guideline Development Group (GDG) ...comprising expert public health scientists and practitioners to inform the drafting of the 2020 Guidelines on Physical Activity and Sedentary Behavior. The overall task of the GDG was to review the scientific evidence and provide expert advice to the WHO on the amount of physical activity and sedentary behavior associated with optimal health in children and adolescents, adults, older adults (> 64 years), and also specifically in pregnant and postpartum women and people living with chronic conditions or disabilities.
The GDG reviewed the available evidence specific to each sub-population using systematic protocols and in doing so, identified a number of gaps in the existing literature. These proposed research gaps were discussed and verified by expert consensus among the entire GDG.
Evidence gaps across population sub-groups included a lack of information on: 1) the precise shape of the dose-response curve between physical activity and/or sedentary behavior and several of the health outcomes studied; 2) the health benefits of light-intensity physical activity and of breaking up sedentary time with light-intensity activity; 3) differences in the health effects of different types and domains of physical activity (leisure-time; occupational; transportation; household; education) and of sedentary behavior (occupational; screen time; television viewing); and 4) the joint association between physical activity and sedentary time with health outcomes across the life course. In addition, we acknowledge the need to conduct more population-based studies in low- and middle-income countries and in people living with disabilities and/or chronic disease, and to identify how various sociodemographic factors (age, sex, race/ethnicity, socioeconomic status) modify the health effects of physical activity, in order to address global health disparities.
Although the 2020 WHO Guidelines for Physical Activity and Sedentary Behavior were informed by the most up-to-date research on the health effects of physical activity and sedentary time, there is still substantial work to be done in advancing the global physical activity agenda.
Breast cancer is the most commonly diagnosed invasive malignancy and the second leading cause of cancer death in women globally. This review considers epidemiologic evidence regarding the association ...between physical activity and breast cancer risk. Across these studies there was a 25% average risk reduction among 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 among 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 are related to breast cancer risk reduction.
Breast cancer remains a leading cause of cancer incidence and mortality in most developed countries worldwide. While significant international research has examined risk factors for breast cancer, most identified risk factors are nonmodifiable. During the past 20 years, over 90 studies have been conducted worldwide that have examined some aspects of the association between physical activity and breast cancer risk reduction. The purpose of this chapter is to review both the epidemiologic evidence and hypothesized biologic mechanisms whereby physical activity may influence breast cancer risk.
To describe new WHO 2020 guidelines on physical activity and sedentary behaviour.
The guidelines were developed in accordance with WHO protocols. An expert Guideline Development Group reviewed ...evidence to assess associations between physical activity and sedentary behaviour for an agreed set of health outcomes and population groups. The assessment used and systematically updated recent relevant systematic reviews; new primary reviews addressed additional health outcomes or subpopulations.
The new guidelines address children, adolescents, adults, older adults and include new specific recommendations for pregnant and postpartum women and people living with chronic conditions or disability. All adults should undertake 150-300 min of moderate-intensity, or 75-150 min of vigorous-intensity physical activity, or some equivalent combination of moderate-intensity and vigorous-intensity aerobic physical activity, per week. Among children and adolescents, an average of 60 min/day of moderate-to-vigorous intensity aerobic physical activity across the week provides health benefits. The guidelines recommend regular muscle-strengthening activity for all age groups. Additionally, reducing sedentary behaviours is recommended across all age groups and abilities, although evidence was insufficient to quantify a sedentary behaviour threshold.
These 2020 WHO guidelines update previous WHO recommendations released in 2010. They reaffirm messages that some physical activity is better than none, that more physical activity is better for optimal health outcomes and provide a new recommendation on reducing sedentary behaviours. These guidelines highlight the importance of regularly undertaking both aerobic and muscle strengthening activities and for the first time, there are specific recommendations for specific populations including for pregnant and postpartum women and people living with chronic conditions or disability. These guidelines should be used to inform national health policies aligned with the
and to strengthen surveillance systems that track progress towards national and global targets.
Endometrial cancers have long been divided into estrogen-dependent type I and the less common clinically aggressive estrogen-independent type II. Little is known about risk factors for type II tumors ...because most studies lack sufficient cases to study these much less common tumors separately. We examined whether so-called classical endometrial cancer risk factors also influence the risk of type II tumors.
Individual-level data from 10 cohort and 14 case-control studies from the Epidemiology of Endometrial Cancer Consortium were pooled. A total of 14,069 endometrial cancer cases and 35,312 controls were included. We classified endometrioid (n = 7,246), adenocarcinoma not otherwise specified (n = 4,830), and adenocarcinoma with squamous differentiation (n = 777) as type I tumors and serous (n = 508) and mixed cell (n = 346) as type II tumors.
Parity, oral contraceptive use, cigarette smoking, age at menarche, and diabetes were associated with type I and type II tumors to similar extents. Body mass index, however, had a greater effect on type I tumors than on type II tumors: odds ratio (OR) per 2 kg/m(2) increase was 1.20 (95% CI, 1.19 to 1.21) for type I and 1.12 (95% CI, 1.09 to 1.14) for type II tumors (P heterogeneity < .0001). Risk factor patterns for high-grade endometrioid tumors and type II tumors were similar.
The results of this pooled analysis suggest that the two endometrial cancer types share many common etiologic factors. The etiology of type II tumors may, therefore, not be completely estrogen independent, as previously believed.
The role of circulating miRNAs (c-miRNAs) in carcinogenesis has garnered considerable scientific interest. miRNAs may contribute actively to cancer development and progression, making them potential ...targets for cancer prevention and therapy. Lifestyle factors such as physical activity (PA) have been shown to alter c-miRNA expression, but the subsequent impact on cancer risk and prognosis is unknown. To provide a better understanding of how PA reduces the risk of cancer incidence and improves patient outcomes, we conducted a review of the impact of PA on c-miRNA expression, which includes a comprehensive synthesis of studies examining the impacts of acute and chronic exercise on expression of c-miRNAs. While the variability in methods used to assess miRNA expression creates challenges in comparing and/or synthesizing the literature, results to date suggest that the circulating form of several miRNAs known for playing a role in cancer (c-miR-133, c-miR-221/222, c-miR-126, and c-let-7) are altered by both acute and chronic PA. Additional research should develop standardized procedures for assessing both c-miRNA and PA measurement to improve the comparability of research results regarding the direction and amplitude of changes in c-miRNAs in response to PA.
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Purpose
In this systematic review and meta-analysis, we aimed to estimate cancer-specific mortality and all-cause mortality among cancer survivors associated with both short (typically 5 or ...6 h/night) and long (typically 9 or 10 h/night) sleep duration (versus recommendations), separately by sex, cancer site, and sampling frame.
Methods
We completed a systematic literature search in five databases and captured relevant literature published through December 2018. Two reviewers independently screened 9,823 records and 32 studies were included representing over 73,000 deaths in cancer survivors. Estimates for short and long sleep duration compared to ‘recommended’ were pooled using random-effects models.
Results
Pooled hazards ratios for short and long sleep duration for all-cancer-specific mortality were 1.03 (95% CI 1.00–1.06) and 1.09 (95% CI 1.04–1.13), respectively. In subgroup analyses by cancer site, statistically significant increased risks were found for both short and long sleep durations for lung cancer-specific mortality. These associations were maintained when stratified by sex and sampling frame. There were no statistically significant associations found between either short or long sleep duration and breast, colorectal, ovarian, or prostate cancer-specific mortality. Statistically significant increases in all-cause mortality were observed with long sleep duration in breast cancer survivors (1.38; 95% CI 1.16–1.64) with no significant associations found for colorectal or liver/pancreatic cancers.
Conclusions
We observed that long sleep duration increases cancer-specific mortality for all-cancers and lung cancers, while all-cause mortality is increased for breast cancer survivors. Limitations were found within the existing literature that need to be addressed in future studies in order to improve the understanding regarding the exact magnitude of the effect between sleep duration and site-specific mortality.
Observational studies suggest that physical activity after a breast cancer diagnosis is associated with improved cancer outcomes; however, no randomized data are available. Here, we report an ...exploratory follow-up of cancer outcomes from the Supervised Trial of Aerobic versus Resistance Training (START).
The START was a Canadian multicenter trial that randomized 242 breast cancer patients between 2003 and 2005 to usual care (n = 82), supervised aerobic (n = 78), or resistance (n = 82) exercise during chemotherapy. The primary end point for this exploratory analysis was disease-free survival (DFS). Secondary end points were overall survival, distant DFS, and recurrence-free interval. The two exercise arms were combined for analysis (n = 160), and selected subgroups were explored.
After a median follow-up of 89 months, there were 25/160 (15.6%) DFS events in the exercise groups and 18/82 (22.0%) in the control group. Eight-year DFS was 82.7% for the exercise groups compared with 75.6% for the control group (HR, 0.68; 95% confidence interval (CI), 0.37-1.24; log-rank, P = 0.21). Slightly stronger effects were observed for overall survival (HR, 0.60; 95% CI, 0.27-1.33; log-rank, P = 0.21), distant DFS (HR, 0.62; 95% CI, 0.32-1.19; log-rank, P = 0.15), and recurrence-free interval (HR, 0.58; 95% CI, 0.30-1.11; Gray test, P = 0.095). Subgroup analyses suggested potentially stronger exercise effects on DFS for women who were overweight/obese (HR, 0.59; 95% CI, 0.27-1.27), had stage II/III cancer (HR, 0.61; 95% CI, 0.31-1.20), estrogen receptor-positive tumors (HR, 0.58; 95% CI, 0.26-1.29), human epidermal growth factor receptor 2-positive tumors (HR, 0.21; 95% CI, 0.04-1.02), received taxane-based chemotherapies (HR, 0.46; 95% CI, 0.19-1.15), and ≥85% of their planned chemotherapy (HR, 0.50; 95% CI, 0.25-1.01).
This exploratory follow-up of the START provides the first randomized data to suggest that adding exercise to standard chemotherapy may improve breast cancer outcomes. A definitive phase III trial is warranted.
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