Cancer incidence due to excess body weight and leisure-time physical inactivity in Canada: implications for prevention

Estimating cancers attributable to physical inactivity in Australia

OBJECTIVES

It was previously estimated that 1814 (1.6 % of incident cancers) were attributable to physical inactivity in Australia in 2010, when only three sites were considered. We estimated the burden of cancer due to physical inactivity in Australia for 13 sites.

DESIGN

The population attributable fraction estimated site-specific cancer cases attributable to physical inactivity for 13 cancers. The potential impact fraction was used to estimate cancers that could have been prevented in 2015 if Australian adults had increased their physical activity by a modest amount in 2004-05.

METHODS

We used 2004-05 national physical activity prevalence data, 2015 national cancer incidence data, and contemporary relative-risk estimates for physical inactivity and cancer. We assumed a 10-year latency period.

RESULTS

An estimated 6361 of the cancers observed in 2015 were attributable to physical inactivity, representing 4.8 % of all cancers diagnosed. If Australian adults had increased their physical activity by one category in 2004-05, 2564 cases (1.9 % of all cancers) could have been prevented in 2015.

CONCLUSIONS

More than three times as many cancers are attributable to physical inactivity than previously reported. Physical activity promotion should be a central component of cancer prevention programmes in Australia.

Population attributable proportion and number of cancer cases attributed to potentially modifiable risk factors in Iran in 2020

In the current study, we aimed to calculate the fraction of cancer attributable to modifiable risk factors in Iran in 2020. Population attributable fractions (PAFs) were calculated for established cancer risk factors using three data sources: the national cancer incidence reports, relative risks extracted from global and national meta-analyses, and exposure prevalence from national/subnational population-based surveys. In addition to overall cancers, the PAFs were estimated separately for each cancer site among men and women. Overall, 32.6% of cancers in 2020 in Iran were attributable to known risk factors. The PAF in men (40.2%) was twice as high as in women (21.1%). Cigarette smoking (15.4%), being overweight (5.0%), opium use (3.9%) and H. pylori infection (3.8%) were the leading causes of cancers. For men, the highest PAFs belonged to cigarette smoking (26.3%), opium use (6.8%) and being overweight (3.1%), while for women, the highest PAFs belonged to being overweight (7.2%), H. pylori infection (2.7%) and cigarette smoking (2.7%). Among Iranian men and women, the PAFs of waterpipe smoking were 2% and 0.9%, respectively. A third of incident cancers in Iran are due to modifiable exposures, mainly cigarette smoking, being overweight, and H. pylori infection. Opium consumption and waterpipe smoking collectively accounted for 8.8% of cancer occurrence in men and 1.3% in women in Iran. These emerging risk factors should be taken into consideration in future PAF studies.

Cumulative evidence for the relationship between body mass index and the risk of esophageal cancer: An updated meta-analysis with evidence from 25 observational studies

BACKGROUND AND AIM

A large number of papers reporting the relationships between body mass index (BMI) and esophageal cancer (EC) risk have been published in the past few decades; however, these results are inconsistent. Therefore, we carried out meta-analyses to explore the relationships between BMI and the risk of EC (including esophageal squamous cell carcinoma [ESCC] and esophageal adenocarcinoma [EADC]).

METHODS

We used the Web of Science, PubMed, and Embase to identify all published/online articles before December 30, 2018, which yielded 25 articles eligible for data extraction (including 16,561 cases and 11,954,161 controls), and then pooled the relative risks (RRs) and corresponding 95% confidence intervals (CIs) using random-effects model.

RESULTS

Our study presented that underweight had statistically significant association with the risk of EC (RR = 1.78, 95% CI = 1.48, 2.14, P < 0.001) and ESCC (RR = 1.57, 95% CI = 1.20, 2.06, P = 0.001) when compared with normal weight. Interestingly, both overweight and obesity could increase the risk of EADC (RR = 1.56, 95% CI = 1.42, 1.71, P < 0.001; RR = 2.34, 95% CI = 2.02, 2.70, P < 0.001) while decrease the risk of ESCC (RR = 0.71, 95% CI = 0.60, 0.84, P < 0.001; RR = 0.63, 95% CI = 0.60, 0.84, P = 0.002). Additionally, obesity could increase the risk of EC (RR = 1.51, 95% CI = 1.21, 1.89, P < 0.001).

CONCLUSION

These meta-analyses provide a comprehensive and updated epidemiological evidence to confirm the associations between BMI and EC risk. These findings have public health implications with respect to better control bodyweight and then reduce the occurrence of EC (including ESCC and EADC).

Case-control study of endogenous sex steroid hormones and risk of endometrial cancer

BACKGROUND

Epidemiologic evidence regarding the role of endogenous sex hormones in endometrial cancer etiology remains inconsistent. The objective of this study was to investigate if circulating levels of endogenous estrone, estradiol, sex hormone binding globulin (SHBG), testosterone, and androstenedione are associated with endometrial cancer risk.

METHODS

We conducted a population-based case-control study of 522 incident endometrial cancer cases and 976 population controls, in Alberta, Canada from 2002 to 2006. Study participants completed in-person interviews and provided fasting blood samples. Sex hormone levels were determined by enzyme-linked immunosorbent assays.

RESULTS

Higher levels of androstenedione were associated with increased endometrial cancer risk (OR 1.44, 95% CI 1.04-2.02). Endometrial cancer risk in pre- and peri-menopausal women was reduced for the highest versus lowest quartiles of estrone (OR 0.44, 95% CI 0.22-0.88) and estradiol (OR 0.30, 95% CI 0.14-0.65), but in post-menopausal women, the endometrial cancer risk was increased for the highest versus lowest quartile of androstenedione (OR 1.82, 95% CI 1.25-2.65). In addition, endometrial cancer risk in normal/underweight women was decreased for the highest versus lowest quartile of serum SHBG (OR 0.39, 95% CI 0.19-0.84).

CONCLUSIONS

Overall, positive associations were found for androstenedione concentrations, while sub-group analyses revealed = inverse associations with estrogens and SHBG. Results of this study provide empirical evidence for the role of circulating sex hormones in endometrial cancer etiology and highlight the importance of modifiable factors that contribute to changes in sex hormone concentration levels.

Estimates of the current and future burden of cancer attributable to lack of physical activity in Canada

Physical activity reduces the risk of many cancers, yet the prevalence of inadequate physical activity among Canadians remains high. Here we estimated the current attributable and future avoidable burden of cancer related to inadequate physical activity among Canadian adults. Population attributable risk (PAR) for all cancers associated with inadequate physical activity were estimated using relative risks obtained from comprehensive reports, meta-analyses and pooled analyses. Cancer incidence data were acquired from the Canadian Cancer Registry. Physical activity data were taken from Canadian Community Health Survey (Cycle 2.1, 2003), in which respondents were classified as "physically inactive" (<1.5 kcal/kg/day), "moderately active" (1.5-2.9 kcal/kg/day) or "physically active (≥3.0 kcal/kg/day). We defined "inadequate physical activity" as being either "physically inactive" or "moderately active" to determine the PAR of cancer due to inadequate physical activity. We estimated the future burden of inadequate physical activity using potential impact fractions and a series of intervention scenarios, including 10% to 50% reductions in inadequate physical activity from 2015 to 2042. For 2015, the total attributable burden due to inadequate physical activity for associated cancers was 10.6% and 4.9% for all cancers. A 50% reduction in inadequate physical activity could avoid 39,877 cumulative cases of cancer by 2042. Over 9000 cancer cases in 2015 were estimated to be attributable to inadequate physical activity and 5170 incident cases of cancer could be prevented with increases in physical activity levels by 2042. Policies aimed at increasing physical activity among Canadian could have a meaningful impact for cancer prevention.

Estimates of the current and future burden of cancer attributable to excess body weight and abdominal adiposity in Canada

The increasing prevalence of obesity among Canadians has important implications for newly diagnosed cases of cancer given that excess body weight and abdominal adiposity are known to increase the risk of several cancers. The purpose of this analysis was to estimate the current attributable and future avoidable burden of cancer related to excess body weight and abdominal adiposity among Canadian adults. We estimated the population attributable risk (PAR) for all cancers associated with excess body weight and abdominal adiposity using contemporary cancer incidence, relative risk and exposure prevalence data for body mass index (BMI), waist circumference and waist-to-hip-ratio. Using the partial impact fraction (PIF), we also estimated the future avoidable burden of cancer from 2015 to 2042 in Canada, and by province, through various hypothetical intervention scenarios. In 2003, approximately half (50.5%) of the Canadian population was estimated to be overweight (BMI 25.0-29.9) or obese (BMI ≥30.0), 56.5% to have excess abdominal adiposity and 56.8% with a high waist-to-hip ratio. In 2015, the estimated PARs of all incident cancers associated with excess body weight, excess abdominal adiposity and high waist-to-hip ratio were 7.2%, 8.9% and 10.0%, respectively. If the population BMI could revert to its 1994 distribution, 72,157 associated cancer cases could be prevented cumulatively by 2042. A reduction in excess body weight and abdominal adiposity has the potential to decrease the future cancer burden in Canada substantially, and hence efforts to reverse increasing trends in obesity should be prioritized.

The burden of cancer attributable to modifiable risk factors in Canada: Methods overview

Up-to-date estimates of current and projected future cancer burden attributable to various exposures are essential for planning and implementing cancer prevention initiatives. The Canadian Population Attributable Risk of Cancer (ComPARe) study was conducted to: i) estimate the number and proportion of cancers diagnosed among adults in Canada in 2015 that are attributable to modifiable risk factors and ii) project the future avoidable cancers by 2042 under various intervention targets. We estimated the population attributable risk (with 95% confidence intervals) and the potential impact fraction of cancers associated with selected lifestyle, environmental, and infectious factors. Exposure-specific sensitivity analyses were also completed where appropriate. Several exposures of interest included active and passive smoking, obesity and abdominal adiposity, leisure-time physical inactivity, sedentary behaviour, alcohol consumption, insufficient fruit and vegetable intake, red and processed meat consumption, air pollution (PM2.5, NO₂), indoor radon gas, ultraviolet radiation (UVR), hepatitis B and C virus, Helicobacter pylori, Epstein-Barr virus, human papillomavirus, human herpesvirus type 8 and human T-cell lymphotropic virus type 1. We used the 2015 cancer incidence data for 35 cancer sites from the Canadian Cancer Registry and projected cancer incidence to 2042 using historical data from 1983 to 2012. Here, we provide an overview of the data sources and methods used in estimating the current and future cancer burden in Canada. Specific methodologic details for each exposure are included in the individual articles included as part of this special issue.

The preventable burden of endometrial and ovarian cancers in Australia: A pooled cohort study

OBJECTIVE

Evidence on the endometrial and ovarian cancer burden preventable through modifications to current causal behavioural and hormonal exposures is limited. Whether the burden differs by population subgroup is unknown.

METHODS

We linked pooled data from six Australian cohort studies to national cancer and death registries, and quantified exposure-cancer associations using adjusted proportional hazards models. We estimated exposure prevalence from representative health surveys. We then calculated Population Attributable Fractions (PAFs) with 95% confidence intervals (CIs), accounting for competing risk of death, and compared PAFs for population subgroups.

RESULTS

During a median 4.9 years follow-up, 510 incident endometrial and 303 ovarian cancers were diagnosed. Overweight and obesity explained 41.9% (95% CI 32.3-50.1) of the endometrial cancer burden and obesity alone 34.5% (95% CI 27.5-40.9). This translates to 12,800 and 10,500 endometrial cancers in Australia in the next 10 years, respectively. The body fatness-related endometrial cancer burden was highest (49-87%) among women with diabetes, living remotely, of older age, lower socio-economic status or educational attainment and born in Australia. Never use of oral contraceptives (OCs) explained 8.1% (95% CI 1.8-14.1) or 2500 endometrial cancers. A higher BMI and current long-term MHT use increased, and long-term OC use decreased, the risk of ovarian cancer, but the burden attributable to overweight, obesity or exogenous hormonal factors was not statistically significant.

CONCLUSIONS

Excess body fatness, a trait that is of high and increasing prevalence globally, is responsible for a large proportion of the endometrial cancer burden, indicating the need for effective strategies to reduce adiposity.

Physical Activity and Gastrointestinal Cancer Risk: A Review

Introduction: Western lifestyle characterized by increased consumption of red meat, fat, processed food, smoking, alcohol drinking, lower consumption of vegetables and physical inactivity has been associated with a higher gastrointestinal cancer risk. Digestive system cancers are diagnosed at late stages when they show poor response to treatment and are associated with a high mortality rate. Colorectal, gastric, esophageal and pancreatic cancers are among the most common cancers worldwide. Studies show that more than 50% of gastrointestinal cancers develop as a result of inappropriate lifestyle. An inverse association between physical activity and many chronic diseases has been proved so far. However, the association between physical activity and some gastrointestinal cancers is still controversial. This study was aimed to determine the association between physical activity and gastrointestinal cancers risk.

Methods: We conducted a comprehensive search of English and Persian databases from February 2007 till December 2017, for studies investigating the association of physical activity and risk of gastrointestinal cancers. Finally, after reading full text of articles, 123 studies were included.

Results: Physical activity can be helpful in reducing the risk of gastrointestinal cancer, especially colon and pancreatic cancers. The risk reduction is not similar for different types of gastrointestinal cancers and also among males and females.

Conclusion: Different types of physical activity are associated with a lower risk of gastrointestinal cancer. However, it is unknown which type and intensity of physical activity are associated with a protective effect against gastro-intestinal cancer.

Avoidable cancers in the Nordic countries-the potential impact of increased physical activity on postmenopausal breast, colon and endometrial cancer

BACKGROUND

Physical activity has been shown to reduce the risk of colon, endometrial and postmenopausal breast cancer. The aim of this study was to quantify the proportion of the cancer burden in the Nordic countries linked to insufficient levels of leisure time physical activity and estimate the potential for cancer prevention for these three sites by increasing physical activity levels.

METHODS

Using the Prevent macrosimulation model, the number of cancer cases in the Nordic countries over a 30-year period (2016-2045) was modelled, under different scenarios of increasing physical activity levels in the population, and compared with the projected number of cases if constant physical activity prevailed. Physical activity (moderate and vigorous) was categorised according to metabolic equivalents (MET) hours in groups with sufficient physical activity (15+ MET-hours/week), low deficit (9 to <15 MET-hours/week), medium deficit (3 to <9 MET-hours/week) and high deficit (<3 MET-hours/week).

RESULTS

If no one had insufficient levels of physical activity, about 11,000 colon, endometrial and postmenopausal breast cancer cases could be avoided in the Nordic countries in a 30-year period, which is 1% of the expected cases for the three cancer types. With a 50% reduction in all deficit groups by 2025 or a 100% reduction in the group of high deficit, approximately 0.5% of the expected cases for the three cancer types could be avoided. The number and percentage of avoidable cases was highest for colon cancer.

CONCLUSION

11,000 cancer cases could be avoided in the Nordic countries in a 30-year period, if deficit in physical activity was eliminated.

Preventable fractions of colon and breast cancers by increasing physical activity in Brazil: perspectives from plausible counterfactual scenarios

BACKGROUND

Physical activity is associated with lower risk of colon and breast cancers. Herein we estimated preventable fractions of colon and breast cancers in Brazil by increasing population-wide physical activity to different counterfactual scenarios.

METHODS

We used data from a representative national survey in Brazil and corresponding relative risks of colon and postmenopausal breast cancers from a meta-analysis. Estimated cancer incidence was retrieved from GLOBOCAN and Brazilian National Cancer Institute. Five counterfactual scenarios for physical activity were considered: (i) theoretical minimum risk exposure level (≥8,000 metabolic equivalent of tasks-minute/week - MET-min/week); (ii) physical activity recommendation (≥600 MET-min/week); (iii) a 10% reduction in prevalence of insufficient physical inactivity (<600 MET-min/week); (iv) physical activity level in each state equals the most active state in Brazil; (v) closing the gender differences in physical activity.

RESULTS

About 19% (3,630 cases) of colon cancers and 12% (6,712 cases) of postmenopausal breast cancers could be prevented by increasing physical activity to ≥8,000 MET-min/week. Plausible counterfactual scenarios suggested the following impact on cancer prevention: reaching physical activity recommendation: 1.7% (1,113 cases) of breast and 6% (1,137 cases) of colon; 10% reduction in physical inactivity prevalence: 0.2% (111 cases) of breast and 0.6% (114 cases) of colon; most active state scenario: 0.3% (168 cases) of breast and 1% (189 cases) of colon; reducing gender differences in physical activity: 1.1% (384 cases) of breast and 0.6% (122 cases) of colon.

CONCLUSIONS

High levels of physical activity are required to achieve a sizable impact on breast and colon cancer prevention in Brazil.

Leitzmann M, Brenner*2 H, Mons*2 U. Cancers Due to Excess Weight, Low Physical Activity, and Unhealthy Diet

BACKGROUND

Excess weight, low physical activity, low intakes of dietary fiber, fruits, and vegetables, and high meat and salt intake increase cancer risk.

METHODS

Numbers and proportions (population-attributable fractions, PAF) of incident cancer cases in Germany in 2018 attributable to these factors were estimated by sex and age groups for ages 35 to 84 years using population projections, national cancer incidence and exposure data, and published risk estimates.

RESULTS

Estimated numbers (percentages) of attributable cancers were 30 567 (7%) for excess weight, 27 081 (6%) for low physical activity, 14 474 (3%) for low dietary fiber intake, 9447 (2%) for low fruit and vegetable consumption, 9454 (2%) and 1687 (0.4%) for processed meat and high red meat consumption, respectively, and 1204 (0.3%) for high salt intake. Excess weight substantially contributed to endometrial, renal, and liver cancer (PAF = 24 to 35%). Low physical activity contributed to endometrial, renal, and lung cancer (PAF = 15 to 19%), and dietary factors mainly contributed to colorectal, breast, and lung cancer (PAF = 9 to 16%).

CONCLUSION

A considerable proportion of cancer cases are attributable to excess weight, physical inactivity, and unhealthy dietary habits. Major prevention efforts are needed to reduce the cancer incidence attributable to these avoidable factors.

Prepregnancy obesity: a risk factor for future development of ovarian and breast cancer

The aim of this study was to investigate the association between a history of prepregnancy obesity and a woman's future long-term risk for the development of female malignancies. A population-based study compared the incidence of long-term female malignancies in a cohort of consecutive women with and without a diagnosis of prepregnancy obesity. Deliveries occurred between the years 1988 and 2013, with a mean follow-up duration of 11.6 years. Women with known malignancies before the index pregnancy and known genetic predisposition for malignancy were excluded from the study. Female malignancies were divided according to specific type (ovary, uterine, breast, and uterine cervix). A Kaplan-Meier survival curve was used to estimate the cumulative incidence of malignancies. A Cox proportional hazards model was used to estimate the adjusted hazard ratios for female malignancy. During the study period, 106 251 deliveries fulfilled the inclusion criteria; 2.2% (n=2360) occurred in patients with a history of prepregnancy obesity. During the follow-up period, patients with prepregnancy obesity had a significantly increased risk for hospitalization because of female malignancies as a group and specifically ovarian and breast cancer. Using a Kaplan-Meier survival curve, patients with a previous diagnosis of prepregnancy obesity had a significantly higher cumulative incidence of female malignancies. Using a Cox proportional hazards model, adjusted for confounders such as gestational diabetes mellitus and maternal age, prepregnancy obesity remained independently associated with long-term risk for female malignancies (adjusted hazard ratio: 1.4; 95% confidence interval: 1.1-1.9; P=0.045). Prepregnancy obesity is an independent risk factor for long-term female malignancies such as ovarian and breast cancer.

LIFETIME PHYSICAL INACTIVITY IS ASSOCIATED WITH LUNG CANCER RISK AND MORTALITY

INTRODUCTION

Investigations of the independent associations of physical inactivity with cancer endpoints have been mounting in the epidemiological literature, in part due to the high prevalence of physical inactivity among cancer patients and to evidence that inactivity associates with carcinogenesis via pathways independent of obesity. Yet, physical inactivity is not currently recognized as a well-established risk or prognostic factor for lung cancer. As such, we examined the associations of lifetime physical inactivity with lung cancer risk and mortality in a hospital-based, case-control study.

PRESENTATION OF CASE

Materials and Methods: The analyses included data from 660 lung cancer patients and 1335 matched cancer-free controls. Multivariable logistic regression analyses were utilized to assess the association between lifetime physical inactivity and lung cancer risk, and Cox proportional hazards models were utilized to estimate the association between lifetime physical inactivity and mortality among lung cancer cases.Results: We observed a significant positive association between lifetime physical inactivity and lung cancer risk: [Odds ratio (OR)=2.23, 95% confidence interval (CI): 1.77-2.81]; the association remained significant among never smokers (OR=3.00, 95% CI:1.33-6.78) and non-smokers (OR=2.33, 95% CI: 1.79-3.02). We also observed a significant positive association between lifetime physical inactivity and lung cancer mortality [Hazard ratio (HR)=1.40, 95% CI: 1.14-1.71]; the association remained significant in non-smokers (HR=1.51, 95% CI: 1.16-1.95).

DISCUSSION/CONCLUSION

These data add to the body of evidence suggesting that physical inactivity is an independent risk and prognostic factor for cancer. Additional research utilizing prospectively collected data is needed to substantiate the current findings.

Cohort profile: a nationwide cohort of Finnish military recruits born in 1958 to study the impact of lifestyle factors in early adulthood on disease outcomes

PURPOSE

The cohort was set up to study the impact of lifestyle factors in early adulthood on disease outcomes, with a focus on assessing the influence of body composition and physical performance in early adulthood on subsequent cancer risk.

PARTICIPANTS

Men born in 1958 who performed their military service between the ages of 17 and 30 years were included in this study (n=31 158). They were eligible for military service if they were healthy or had only minor health problems diagnosed at the beginning of their service. Men with chronic illnesses requiring regular medication or treatment were not eligible for service. Comprehensive health data including diagnosed illnesses, anthropometric measures and health behaviour were collected at the beginning and at the end of military service, including data from medical check-ups.

FINDINGS TO DATE

During the follow-up, 1124 new cancer cases were diagnosed between baseline (ie, end of the military service for each individual) and end of the year 2014. In the end of the follow-up, 91% of the study participants were still alive. Overweight (body mass index (BMI) ≥25 kg/m2) and obesity (BMI ≥30 kg/m2) were associated with an overall increased risk of cancer. A good or excellent physical condition significantly reduced cancer risk.

FUTURE PLANS

The dataset offers the possibility of linkage with other databases, such as the Finnish Cancer Registry (eg, primary site of the tumour, morphology, time of detection, spreading and primary treatment), vital statistics (date of emigration or deaths), censuses (socioeconomic indicators), hospital discharge data (comorbidity) and population surveys (life habits).

Increased level of DNA damage in some organs of obese Zucker rats by γ-H2AX analysis

In a recent study, we showed that lymphocytes of obese Italian children/adolescents displayed levels of double strand breaks (DSB), assayed as serine 139-phosphorylated histone H2AX (γ-H2AX), about eightfold higher than normal weight controls, and that 30% of this damage-generated micronuclei. These findings suggested that obese children could be at increased risk of obesity-mediated cancer later in life. We therefore aimed to assess the level of γ-H2AX in a genetic animal model of obesity (Zucker rat) to identify a genotoxic/carcinogenic risk in some organs. The DSB marker was studied in 3- to 4-week-old rats and in 9- to 13-week-old rats. Paraffin-embedded sections of heart, thyroid, liver, pancreas, lung, kidney, esophagus, and gut from the fa-/fa- (obese) and the fa+/fa- (lean) control animals were processed for immunohistochemistry detection of γ-H2AX. Pancreas (0.0624 ± 0.0195), lung (0.1197 ± 0.0217), esophagus (0.1230 ± 0.0351), kidney (0.1546 ± 0.0149), and gut (0.1724 ± 0.0352) of 9- to 13-week-old obese rats showed a higher proportion of γ-H2AX-positive nuclei, than their lean counterparts (0.0092 ± 0.0033, 0.0416 ± 0.0185, 0.0368 ± 0.0088, 0.0686 ± 0.0318, and 0.0703 ± 0.0239, respectively). No difference was seen in the 3- to 4-week-old age group with regard to obesity, indicating that the DNA damage increased with older age of the rats. We hypothesize that the organs of the obese animals showing high levels of DSB could represent target tissues for the development of obesity-related cancers. Environ. Mol. Mutagen. 58:477-484, 2017. © 2017 Wiley Periodicals, Inc.

Cancers attributable to excess body weight in Canada in 2010

INTRODUCTION

Excess body weight (body mass index [BMI] ≥ 25.00 kg/m2) is an established risk factor for diabetes, hypertension and cardiovascular disease, but its relationship to cancer is lesser-known. This study used population attributable fractions (PAFs) to estimate the cancer burden attributable to excess body weight in Canadian adults (aged 25+ years) in 2010.

METHODS

We estimated PAFs using relative risk (RR) estimates from the World Cancer Research Fund International Continuous Update Project, BMI-based estimates of overweight (25.00 kg/m2-29.99 kg/m2) and obesity (30.00+ kg/m2) from the 2000-2001 Canadian Community Health Survey, and cancer case counts from the Canadian Cancer Registry. PAFs were based on BMI corrected for the bias in self-reported height and weight.

RESULTS

In Canada in 2010, an estimated 9645 cancer cases were attributable to excess body weight, representing 5.7% of all cancer cases (males 4.9%, females 6.5%). When limiting the analysis to types of cancer associated with high BMI, the PAF increased to 14.9% (males 17.5%, females 13.3%). Types of cancer with the highest PAFs were esophageal adenocarcinoma (42.2%), kidney (25.4%), gastric cardia (20.7%), liver (20.5%), colon (20.5%) and gallbladder (20.2%) for males, and esophageal adenocarcinoma (36.1%), uterus (35.2%), gallbladder (23.7%) and kidney (23.0%) for females. Types of cancer with the greatest number of attributable cases were colon (1445), kidney (780) and advanced prostate (515) for males, and uterus (1825), postmenopausal breast (1765) and colon (675) for females. Irrespective of sex or type of cancer, PAFs were highest in the Prairies (except Alberta) and the Atlantic region and lowest in British Columbia and Quebec.

CONCLUSION

The cancer burden attributable to excess body weight is substantial and will continue to rise in the near future because of the rising prevalence of overweight and obesity in Canada.

Cancer risks in a population-based study of 70,570 agricultural workers: results from the Canadian census health and Environment cohort (CanCHEC)

BACKGROUND

Agricultural workers may be exposed to potential carcinogens including pesticides, sensitizing agents and solar radiation. Previous studies indicate increased risks of hematopoietic cancers and decreased risks at other sites, possibly due to differences in lifestyle or risk behaviours. We present findings from CanCHEC (Canadian Census Health and Environment Cohort), the largest national population-based cohort of agricultural workers.

METHODS

Statistics Canada created the cohort using deterministic and probabilistic linkage of the 1991 Canadian Long Form Census to National Cancer Registry records for 1992-2010. Self-reported occupations were coded using the Standard Occupational Classification (1991) system. Analyses were restricted to employed persons aged 25-74 years at baseline (N = 2,051,315), with follow-up until December 31, 2010. Hazard ratios (HR) and 95% confidence intervals (CI) were modeled using Cox proportional hazards for all workers in agricultural occupations (n = 70,570; 70.8% male), stratified by sex, and adjusted for age at cohort entry, province of residence, and highest level of education.

RESULTS

A total of 9515 incident cancer cases (7295 in males) occurred in agricultural workers. Among men, increased risks were observed for non-Hodgkin lymphoma (HR = 1.10, 95% CI = 1.00-1.21), prostate (HR = 1.11, 95% CI = 1.06-1.16), melanoma (HR = 1.15, 95% CI = 1.02-1.31), and lip cancer (HR = 2.14, 95% CI = 1.70-2.70). Decreased risks in males were observed for lung, larynx, and liver cancers. Among female agricultural workers there was an increased risk of pancreatic cancer (HR = 1.36, 95% CI = 1.07-1.72). Increased risks of melanoma (HR = 1.79, 95% CI = 1.17-2.73), leukemia (HR = 2.01, 95% CI = 1.24-3.25) and multiple myeloma (HR = 2.25, 95% CI = 1.16-4.37) were observed in a subset of female crop farmers.

CONCLUSIONS

Exposure to pesticides may have contributed to increased risks of hematopoietic cancers, while increased risks of lip cancer and melanoma may be attributed to sun exposure. The array of decreased risks suggests reduced smoking and alcohol consumption in this occupational group compared to the general population.

Cancer incidence attributable to inadequate physical activity in Alberta in 2012

BACKGROUND

Physical inactivity has been consistently associated with increased risk of colorectal, endometrial, breast (in postmenopausal women), prostate, lung and ovarian cancers. The objective of the current analysis was to estimate the proportion and absolute number of site-specific cancer cases attributable to inadequate physical activity in Alberta in 2012.

METHODS

We used population attributable risks to estimate the proportion of each site-specific cancer attributable to inactivity. Relative risk estimates were obtained from the epidemiological literature, and prevalence estimates were calculated with the use of data from the Canadian Community Health Survey cycle 2.1 (2003). Respondents who acquired 1.5-2.9 kcal/kg per day and less than 1.5 kcal/kg per day of physical activity were classified as moderately active and inactive, respectively, and both levels were considered inadequate for mitigating cancer risks. We obtained age-, sex- and site-specific cancer incidence data from the Alberta Cancer Registry for 2012.

RESULTS

About 59%-75% of men and 69%-78% of women did not engage in adequate physical activity. Overall, 13.8% of cancers across all associated cancers were estimated to be attributable to inadequate physical activity, representing 7.2% of all cancers diagnosed in Alberta in 2012. Suboptimal levels of physical activity had a greater impact among women: the proportion of all associated cancers attributable to inadequate physical activity was 18.3% for women and 9.9% for men.

INTERPRETATION

A substantial proportion of cancer cases diagnosed in Alberta were estimated to be attributable to inadequate physical activity. With the high prevalence of physical inactivity among adults in the province, developing strategies to increase physical activity levels could have a notable impact on reducing future cancer burden in Alberta.

Alberta's Tomorrow Project: adherence to cancer prevention recommendations pertaining to diet, physical activity and body size

OBJECTIVE

To explore cross-sectional adherence to cancer prevention recommendations by adults enrolled in a prospective cohort in Alberta, Canada.

DESIGN

Questionnaire data were used to construct a composite cancer prevention adherence score for each participant, based on selected personal recommendations published by the World Cancer Research Fund/American Institute for Cancer Research (2007). Data were self-reported on health and lifestyle, past-year physical activity and past-year FFQ. The scores accounted for physical activity, dietary supplement use, body size, and intakes of alcohol, fruit, vegetables and red meat. Tobacco exposure was also included. Scores ranged from 0 (least adherent) to 7 (most adherent).

SETTING

Alberta's Tomorrow Project; a research platform based on a prospective cohort.

SUBJECTS

Adult men and women (n 24 988) aged 35-69 years recruited by random digit dialling and enrolled in Alberta's Tomorrow Project between 2001 and 2009.

RESULTS

Of the cohort, 14 % achieved adherence scores ≥5 and 60 % had scores ≤3. Overall adherence scores were higher in women (mean (sd): 3·4 (1·1)) than in men (3·0 (1·2)). The extent of overall adherence was also associated with level of education, employment status, annual household income, personal history of chronic disease, family history of chronic disease and age.

CONCLUSIONS

Reported adherence to selected personal recommendations for cancer prevention was low in this cohort of adults. In the short to medium term, these results suggest that more work is required to identify behaviours to target with cancer prevention strategies at a population level. Future work will explore the associations between adherence scores and cancer risk in this cohort.

Cancer incidence attributable to excess body weight in Alberta in 2012

BACKGROUND

Excess body weight has been consistently associated with colorectal, breast, endometrial, esophageal, gall bladder, pancreatic and kidney cancers. The objective of this analysis was to estimate the proportion of total and site-specific cancers attributable to excess body weight in adults in Alberta in 2012.

METHODS

We estimated the proportions of attributable cancers using population attributable risk. Risk estimates were obtained from recent meta-analyses, and exposure prevalence estimates were obtained from the Canadian Community Health Survey. People with a body mass index of 25.00-29.99 kg/m2 and of 30 kg/m2 or more were categorized as overweight and obese, respectively.

RESULTS

About 14%-47% of men and 9%-35% of women in Alberta were classified as either overweight or obese; the proportion increased with increasing age for both sexes. We estimate that roughly 17% and 12% of obesity-related cancers among men and women, respectively, could be attributed to excess body weight in Alberta in 2012. The heaviest absolute burden in terms of number of cases was seen for breast cancer among women and for colorectal cancer among men. Overall, about 5% of all cancers in adults in Alberta in 2012 were estimated to be attributable to excess body weight in 2000-2003.

INTERPRETATION

Excess body weight contributes to a substantial proportion of cases of cancers associated with overweight and obesity annually in Alberta. Strategies to improve energy imbalance and reduce the proportion of obese and overweight Albertans may have a notable impact on cancer incidence in the future.

Recent advances in the link between physical activity, sedentary behavior, physical fitness, and colorectal cancer

Physical inactivity is a well-established risk factor for colorectal cancer (CRC). Recent studies have characterized physical activity (PA), sedentary behavior, and cardiorespiratory fitness as distinct, interrelated constructs that influence the risk of CRC and related outcomes. PA levels required to confer protection against CRC may be higher than previously thought. Sedentary behavior, defined as time spent sitting, increases CRC risk independent of PA and may require novel interventions distinct from those targeting PA. Finally, cardiorespiratory fitness is inversely associated with CRC risk and mortality and may provide a potential tool for risk stratification and intervention.

Theory-Based Interventions Combining Mental Simulation and Planning Techniques to Improve Physical Activity: Null Results from Two Randomized Controlled Trials

Interventions to assist individuals in initiating and maintaining regular participation in physical activity are not always effective. Psychological and behavioral theories advocate the importance of both motivation and volition in interventions to change health behavior. Interventions adopting self-regulation strategies that foster motivational and volitional components may, therefore, have utility in promoting regular physical activity participation. We tested the efficacy of an intervention adopting motivational (mental simulation) and volitional (implementation intentions) components to promote a regular physical activity in two studies. Study 1 adopted a cluster randomized design in which participants (n = 92) were allocated to one of three conditions: mental simulation plus implementation intention, implementation intention only, or control. Study 2 adopted a 2 (mental simulation vs. no mental simulation) × 2 (implementation intention vs. no implementation intention) randomized controlled design in which fitness center attendees (n = 184) were randomly allocated one of four conditions: mental simulation only, implementation intention only, combined, or control. Physical activity behavior was measured by self-report (Study 1) or fitness center attendance (Study 2) at 4- (Studies 1 and 2) and 19- (Study 2 only) week follow-up periods. Findings revealed no statistically significant main or interactive effects of the mental simulation and implementation intention conditions on physical activity outcomes in either study. Findings are in contrast to previous research which has found pervasive effects for both intervention strategies. Findings are discussed in light of study limitations including the relatively small sample sizes, particularly for Study 1, deviations in the operationalization of the intervention components from previous research and the lack of a prompt for a goal intention. Future research should focus on ensuring uniformity in the format of the intervention components, test the effects of each component alone and in combination using standardized measures across multiple samples, and systematically explore effects of candidate moderators.

Role of n-3 Polyunsaturated Fatty Acids and Exercise in Breast Cancer Prevention: Identifying Common Targets

Diet and exercise are recognized as important lifestyle factors that significantly influence breast cancer risk. In particular, dietary n-3 polyunsaturated fatty acids (PUFAs) have been shown to play an important role in breast cancer prevention. Growing evidence also demonstrates a role for exercise in cancer and chronic disease prevention. However, the potential synergistic effect of n-3 PUFA intake and exercise is yet to be determined. This review explores targets for breast cancer prevention that are common between n-3 PUFA intake and exercise and that may be important study outcomes for future research investigating the combined effect of n-3 PUFA intake and exercise. These lines of evidence highlight potential new avenues for research and strategies for breast cancer prevention.

The fractions of cancer attributable to modifiable factors: A global review

Worldwide, the burden of cancer is rising, stimulating efforts to develop strategies to control these diseases. Primary prevention, a key control strategy, aims to reduce cancer incidence through programs directed towards reducing population exposure to known causal factors. Before enacting such strategies, it is necessary to estimate the likely effect on cancer incidence if exposures to known causal factors were reduced or eliminated. The population attributable fraction (PAF) is the epidemiological measure which quantifies this potential reduction in incidence. We surveyed the literature to document and summarise the proportions of cancers across the globe attributable to modifiable causes, specifically tobacco smoke, alcohol, overweight/obesity, insufficient physical activity, solar ultraviolet (UV) radiation and dietary factors (insufficient fruit, non-starchy vegetables and fibre; red/processed meat; salt). In total, we identified 55 articles that presented PAF estimates for one or more causes. Information coverage was not uniform, with many articles reporting cancer PAFs due to overweight/obesity, alcohol and tobacco, but fewer reporting PAFs for dietary factors or solar UV radiation. At all cancer sites attributable to tobacco and alcohol, median PAFs were markedly lower for women than men. Smoking contributed to very high median PAFs (>50%) for cancers of the lung and larynx. Median PAFs for men, attributable to alcohol, were high (25-50%) for cancers of the oesophagus, oral cavity/pharynx, larynx and liver. For cancers causally associated with overweight/obesity, high median PAFs were reported for oesophageal adenocarcinoma (men 29%, women 37%), gallbladder (men 11%, women 42%) and endometrium (36%). The cancer PAF literature is growing rapidly. Repeating this survey in the future should lead to more precise estimates of the potentially preventable fractions of cancer.

A methodologic framework to evaluate the number of cancers attributable to lifestyle and environment in Alberta

BACKGROUND

Previous research to estimate population attributable risks for cancer in Alberta has been limited. Attributable burden estimates are important for planning and implementing population-based cancer prevention strategies. This article describes a methodologic framework to estimate the number of incident cancers attributable to modifiable lifestyle and environmental risk factors in Alberta.

METHODS

We estimated population attributable risks for cancer for exposures to 24 established cancer risk factors including tobacco consumption and environmental tobacco exposure, environmental factors, infectious agents, hormone therapies, dietary intake, obesity and physical inactivity. We used risk estimates to quantify the association between individual exposures and cancer sites as well as prevalence estimates for individual exposures in Alberta to estimate the proportion of cancer in Alberta that could be attributed to each exposure. These estimations were conducted in the context of a theoretical minimum risk principle, whereby exposures corresponding to the lowest levels of population risk were used as the comparisons for alternative exposure levels.

INTE RPRETATION

We outline the main methodologic principles for the protocol used in evaluating population attributable risks for modifiable lifestyle and environmental risk factors for cancer in Alberta. The data produced by this project will provide important information concerning which known cancer risk factors are responsible for the largest proportions of cancer in Alberta and could inform future cancer prevention strategies.

Leisure-time physical activity and lung cancer risk: A systematic review and meta-analysis

OBJECTIVES

We conducted a systematic review and meta-analysis of the association between recreational physical activity and lung cancer risk to update previous analyses and to examine population subgroups of interest defined by smoking status and histology.

MATERIALS AND METHODS

We searched the PubMed database for studies up to May 2015. Individual study characteristics were abstracted including study design, number of cases, assessment of recreational physical activity and type and level of adjustment for confounding factors. Combined effect estimates were calculated for the overall associations and across subgroups of interest.

RESULTS

We identified 28 studies that were eligible for inclusion in the meta-analysis. The overall analysis indicated an inverse association between recreational physical activity and lung cancer risk (Relative Risk (RR), 0.76; 95% Confidence Interval (CI), 0.69-0.85, p-value: <0.001). Similar inverse associations with risk were also noted for all evaluated histological subtypes, including adenocarcinoma (RR, 0.80; 95% CI, 0.72-0.88), squamous (RR, 0.80; 95% CI, 0.71-0.90) and small cell (RR, 0.79; 95% CI, 0.66-0.94). When we examined effects by smoking status, inverse associations between recreational physical activity and lung cancer risk were observed among former (RR, 0.77; 95% CI, 0.69-0.85) and current smokers (RR, 0.77; 95% CI, 0.72-0.83), but not among never smokers (RR, 0.96; 95% CI, 0.79-1.18).

CONCLUSION

Results from this meta-analysis suggest that regular recreational physical activity may be associated with reduced risk of lung cancer. Only four studies examining never smokers were identified, suggesting the need for additional research in this population.

Randomized trial of a phone- and web-based weight loss program for women at elevated breast cancer risk: the HELP study

Excess weight and physical inactivity are modifiable risk factors for breast cancer. Behavioral intervention is particularly important among women with an elevated risk profile. This trial tested an intervention that trained women to use a self-monitoring website to increase activity and lose weight. Women with BMI ≥27.5 kg/m(2) at elevated breast cancer risk were randomized to the intervention (N = 71) or usual care (N = 34). The intervention group received telephone-based coaching and used web-based self-monitoring tools. At 6 months, significant weight loss was observed in the intervention group (4.7 % loss from starting weight; SD = 4.7 %) relative to usual care (0.4 % gain; SD = 3.0 %) (p < 0.0001). By 12 months, the intervention group had lost 3.7 % of weight (SD = 5.4 %), compared to 1.3 % (SD = 4.2) for usual care (p = 0.003). At 12 months, accelerometer-measured moderate-to-vigorous physical activity increased by 12 min/day (SD = 24) compared to no change in usual care (p = 0.04. In summary, this web- and phone-based approach produced modest but significant improvements in weight and physical activity for women at elevated breast cancer risk.

The Fraction of Cancer Attributable to Ways of Life, Infections, Occupation, and Environmental Agents in Brazil in 2020

Many human cancers develop as a result of exposure to risk factors related to the environment and ways of life. The aim of this study was to estimate attributable fractions of 25 types of cancers resulting from exposure to modifiable risk factors in Brazil. The prevalence of exposure to selected risk factors among adults was obtained from population-based surveys conducted from 2000 to 2008. Risk estimates were based on data drawn from meta-analyses or large, high quality studies. Population-attributable fractions (PAF) for a combination of risk factors, as well as the number of preventable deaths and cancer cases, were calculated for 2020. The known preventable risk factors studied will account for 34% of cancer cases among men and 35% among women in 2020, and for 46% and 39% deaths, respectively. The highest attributable fractions were estimated for tobacco smoking, infections, low consumption of fruits and vegetables, excess weight, reproductive factors, and physical inactivity. This is the first study to systematically estimate the fraction of cancer attributable to potentially modifiable risk factors in Brazil. Strategies for primary prevention of tobacco smoking and control of infection and the promotion of a healthy diet and physical activity should be the main priorities in policies for cancer prevention in the country.

Impact of a combined community and primary care prevention strategy on all-cause and cardiovascular mortality: a cohort analysis based on 1 million person-years of follow-up in Västerbotten County, Sweden, during 1990-2006

OBJECTIVE

To evaluate the impact of the Västerbotten Intervention Programme (VIP) by comparing all eligible individuals (target group impact) according to the intention-to-treat principle and VIP participants with the general Swedish population.

DESIGN

Dynamic cohort study.

SETTING/PARTICIPANTS

All individuals aged 40, 50 or 60 years, residing in Västerbotten County, Sweden, between 1990 and 2006 (N=101,918) were followed from their first opportunity to participate in the VIP until age 75, study end point or prior death.

INTERVENTION

The VIP is a systematic, long-term, county-wide cardiovascular disease (CVD) intervention that is performed within the primary healthcare setting and combines individual and population approaches. The core component is a health dialogue based on a physical examination and a comprehensive questionnaire at the ages of 40, 50 and 60 years.

PRIMARY OUTCOMES

All-cause and CVD mortality.

RESULTS

For the target group, there were 5646 deaths observed over 1,054,607 person-years. Compared to Sweden at large, the standardised all-cause mortality ratio was 90.6% (95% CI 88.2% to 93.0%): for women 87.9% (95% CI 84.1% to 91.7%) and for men 92.2% (95% CI 89.2% to 95.3%). For CVD, the ratio was 95.0% (95% CI 90.7% to 99.4%): for women 90.4% (95% CI 82.6% to 98.7%) and for men 96.8% (95% CI 91.7 to 102.0). For participants, subject to further impact as well as selection, when compared to Sweden at large, the standardised all-cause mortality ratio was 66.3% (95% CI 63.7% to 69.0%), whereas the CVD ratio was 68.9% (95% CI 64.2% to 73.9%). For the target group as well as for the participants, standardised mortality ratios for all-cause mortality were reduced within all educational strata.

CONCLUSIONS

The study suggests that the VIP model of CVD prevention is able to impact on all-cause and cardiovascular mortality when evaluated according to the intention-to-treat principle.

Study design and methods for the Breast Cancer and Exercise Trial in Alberta (BETA)

Background

Exercise has favorable effects on biomarkers associated with a lower risk of breast cancer, however it is unclear if higher doses of exercise provide additional effects. No clinical trial has systematically examined how different exercise volumes influence the mechanisms underlying breast cancer etiology. The Breast Cancer and Exercise Trial in Alberta (BETA) - a follow-up study to the Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial - is examining how a one-year, high versus moderate volume aerobic exercise intervention influences several biomechanisms hypothesized to influence breast cancer risk in a group of postmenopausal women. Secondary aims are to compare intervention effects on psychosocial and quality of life outcomes as well as understand exercise adherence at 12 and 24 months, and maintenance of all study outcomes at 24 months.

Methods/Design

The BETA Trial is a two-center, two-armed randomized controlled exercise intervention trial conducted in 400 previously inactive, postmenopausal women aged 50–74 years, in Alberta, Canada. Participants were randomly assigned to a one-year aerobic exercise intervention of either high volume (300 minutes/week) or moderate volume (150 minutes/week). Blood draws and accelerometry were performed at baseline, six and 12 months. Baseline and 12-month measurements were taken of adiposity (including dual energy X-ray absorptiometry and computed tomography scans), physical fitness, dietary intake, self-reported physical activity and sedentary behavior, quality of life, perceived stress, happiness, sleep, and determinants of exercise adherence. Exercise maintenance was assessed and all study measurements were repeated at 24 months. Blood will be analyzed for endogenous estrogens, insulin resistance indicators, and inflammatory markers.

Discussion

The BETA Trial will compare the impact of a high versus moderate volume of aerobic exercise on a variety of biological, physiological, and psychological outcomes of relevance to postmenopausal women. A tightly controlled exercise intervention and objective outcome measurements are methodological strengths. The BETA Trial will inform future prevention initiatives by assessing adherence to a high volume of exercise over 12 months by postmenopausal women, and the ability of these women to maintain activity over the longer-term. The ultimate objective is to inform public health guidelines for reducing breast cancer risk through physical activity.

Trial registration

Clinical Trials Registration Number: NCT01435005