Terry Boyle

Physical Activity and Risks of Proximal and Distal Colon Cancers: A Systematic Review and Meta-analysis

BACKGROUND Although there is convincing epidemiological evidence that physical activity is associated with a reduced risk of colon cancer, it is unclear whether physical activity is differentially associated with the risks of proximal colon and distal colon cancers. We conducted a systematic review and meta-analysis to investigate this issue. METHODS MEDLINE and EMBASE were searched for English-language cohort and case-control studies that examined associations between physical activity and the risks of proximal colon and distal colon cancers. A random-effects meta-analysis was conducted to estimate the summary relative risks (RRs) for the associations between physical activity and the risks of the two cancers. All statistical tests were two-sided. RESULTS A total of 21 studies met the inclusion criteria. The summary relative risk of the main results from these studies indicated that the risk of proximal colon cancer was 27% lower among the most physically active people compared with the least active people (RR = 0.73, 95% confidence interval [CI] = 0.66 to 0.81). An almost identical result was found for distal colon cancer (RR = 0.74, 95% CI = 0.68 to 0.80). CONCLUSION The results of this systematic review and meta-analysis suggest that physical activity is associated with a reduced risk of both proximal colon and distal colon cancers, and that the magnitude of the association does not differ by subsite. Given this finding, future research on physical activity and colon cancer should focus on other aspects of the association that remain unclear, such as whether sedentary behavior and nonaerobic physical activity are associated with the risk of colon cancer.

Hypotheses for mechanisms linking shiftwork and cancer.

Shift work has been associated with various adverse health outcomes. In particular, there has been a recent flourish in investigating potential cancer risk associated with working night shifts and other shift schedules. Epidemiologic studies have revealed generally weak associations due to several methodological challenges such as lack of standard classifications of shift or night work. The field also has been hindered by a lack of clarity about the possible mechanisms by which shiftwork could have an effect on cancer risk. One possible mechanism is reduced production of melatonin caused by exposure to light at night. Although there is a growing body of evidence that provides some support for this mechanism, several other mechanisms also make sense from a biological point of view. Further, the relatively weak magnitude of the associations between light at night and melatonin level suggests that multiple factors may be operating along the pathway between shift work and adverse health consequences (including cancer risk). Here we propose four additional mechanisms that should be considered for a comprehensive investigation of these potential pathways. These are: phase shift; sleep disruption; lifestyle factors (such as poor quality diets, less physical activity and higher BMI); and lower vitamin D. Consideration of all these mechanisms is necessary in order to design effective preventative workplace strategies. In developed countries, approximately 20% of the population undertake shiftwork and, while we are unlikely to be able to eliminate shiftwork from current work practices, there are aspects of shiftwork that can be modified and there may be facets of individual susceptibility that we may be able to identify and target for prevention.

Long-Term Sedentary Work and the Risk of Subsite-specific Colorectal Cancer

Research suggests that sedentary behavior may increase the risk of some chronic diseases. The aims of the study were to examine whether sedentary work is associated with colorectal cancer and to determine whether the association differs by subsite. A total of 918 cases and 1,021 controls participated in a population-based case-control study of colorectal cancer in Western Australia in 2005-2007. Data were collected on lifestyle, physical activity, and lifetime job history. The estimated effects of sedentary work on the risk of cancers of the proximal colon, distal colon, and rectum were analyzed by using multinomial logistic regression. Compared with participants who did not spend any time in sedentary work, participants who spent 10 or more years in sedentary work had almost twice the risk of distal colon cancer (adjusted odds ratio = 1.94, 95% confidence interval: 1.28, 2.93) and a 44% increased risk of rectal cancer (adjusted odds ratio = 1.44, 95% confidence interval: 0.96, 2.18). This association was independent of recreational physical activity and was seen even among the most recreationally active participants. Sedentary work was not associated with the risk of proximal colon cancer. These results suggest that long-term sedentary work may increase the risk of distal colon cancer and rectal cancer.

Associations of objectively assessed physical activity and sedentary time with health-related quality of life among colon cancer survivors

The primary purpose of this study was to determine associations of accelerometer‐assessed moderate‐ to vigorous‐intensity physical activity (MVPA) and sedentary time with health‐related quality of life (HRQoL) and physical function and well‐being in colon cancer survivors.

The Association Between Different Night Shiftwork Factors and Breast Cancer: a Case–Control Study

Background:Research on the possible association between shiftwork and breast cancer is complicated because there are many different shiftwork factors, which might be involved including: light at night, phase shift, sleep disruption and changes in lifestyle factors while on shiftwork (diet, physical activity, alcohol intake and low sun exposure).Methods:We conducted a population-based case–control study in Western Australia from 2009 to 2011 with 1205 incident breast cancer cases and 1789 frequency age-matched controls. A self-administered questionnaire was used to collect demographic, reproductive, and lifestyle factors and lifetime occupational history and a telephone interview was used to obtain further details about the shiftwork factors listed above.Results:A small increase in risk was suggested for those ever doing the graveyard shift (work between midnight and 0500 hours) and breast cancer (odds ratio (OR)=1.16, 95% confidence interval (CI)=0.97–1.39). For phase shift, we found a 22% increase in breast cancer risk (OR=1.22, 95% CI=1.01–1.47) with a statistically significant dose–response relationship (P=0.04). For the other shiftwork factors, risks were marginally elevated and not statistically significant.Conclusion:We found some evidence that some of the factors involved in shiftwork may be associated with breast cancer but the ORs were low and there were inconsistencies in duration and dose–response relationships.

Lifestyle factors associated with survival after colorectal cancer diagnosis

Background:Aside from tumour stage and treatment, little is known about potential factors that may influence survival in colorectal cancer patients. The aim of this study was to investigate the associations between physical activity, obesity and smoking and disease-specific and overall mortality after a colorectal cancer diagnosis.Methods:A cohort of 879 colorectal cancer patients, diagnosed in Western Australia between 2005 and 2007, were followed up to 30 June 2012. Cox’s regression models were used to estimate the hazard ratios (HR) for colorectal cancer-specific and overall mortality associated with self-reported pre-diagnosis physical activity, body mass index (BMI) and smoking.Results:Significantly lower overall and colorectal cancer-specific mortality was seen in females who reported any level of recent physical activity than in females reporting no activity. The colorectal cancer-specific mortality HR for increasing levels of physical activity in females were 0.34 (95% CI=0.15, 0.75), 0.37 (95% CI=0.17, 0.81) and 0.41 (95% CI=0.18, 0.90). Overweight and obese women had almost twice the risk of dying from any cause or colorectal cancer compared with women of normal weight. Females who were current smokers had worse overall and colorectal cancer-specific mortality than never smokers (overall HR=2.64, 95% CI=1.18, 5.93; colorectal cancer-specific HR=2.70, 95% CI=1.16, 6.29). No significant associations were found in males.Conclusion:Physical activity, BMI and smoking may influence survival after a diagnosis of colorectal cancer, with more pronounced results found for females than for males.

Awareness and impact of the ‘Bubblewrap’ advertising campaign among Aboriginal smokers in Western Australia

Background Antismoking mass media campaigns have been shown to reduce smoking prevalence in the mainstream community, however there is little published research on their effect on Aboriginal Australian smokers. Objectives To evaluate the awareness and impact of a mainstream mass media advertising campaign (the ‘Bubblewrap’ campaign) on Aboriginal smokers in the state of Western Australia. Methods A personal intercept survey was conducted in July 2008 across three sites (the Perth metropolitan area and the non-metropolitan towns of Kalgoorlie and Broome). An opportunity or convenience sampling strategy was used to recruit Aboriginal participants, and face-to-face interviews were conducted with 198 Aboriginal smokers to ascertain awareness of the campaign advertisements, whether they were seen as believable and relevant, and the impact the advertisements had on smoking behaviour. Results The majority of the participants interviewed had seen and/or heard the ‘Bubblewrap’ campaign advertisements, although there was considerably greater awareness of the television advertisement than the radio advertisements. Both forms of advertising were considered to be believable and relevant by the majority of Aboriginal smokers. Most of the smokers interviewed thought about cutting down and/or quitting after seeing or hearing the advertisements. Conclusions Our findings suggest that mainstream antismoking mass media campaigns can positively influence the thoughts and behaviours that Aboriginal smokers have, and exhibit, towards quitting smoking. Notwithstanding this, advertisers should continue to look for better ways to incorporate Aboriginal themes in campaign messages. Future mainstream antismoking campaigns should source sufficient funds to ensure that advertising messages reach the large Aboriginal populations in regional and remote Australia.

Accelerometer-assessed physical activity and sedentary time among colon cancer survivors: associations with psychological health outcomes

PurposeThe purpose of this study was to determine associations of objectively assessed moderate-to-vigorous intensity physical activity (MVPA) and sedentary time with psychological health outcomes including depression symptoms, anxiety symptoms, and overall satisfaction with life in colon cancer survivors.MethodsColon cancer survivors (N = 180) from Alberta, Canada (n = 91), and Western Australia (n = 89) completed a mailed survey that assessed depression symptom severity, state anxiety, and satisfaction with life (SWL). Sedentary time and MVPA were assessed using the Actigraph® GT3X+ accelerometer (60-s epochs) via a 7-day monitoring protocol. MVPA and sedentary time were corrected for wear time and then examined as quartiles (Q). Multivariate analysis of variance was used to examine associations of MVPA and sedentary time with psychological health.ResultsThere was a significant association between psychological health outcomes and objectively assessed MVPA [Wilks’ λ = 0.886, F(3382.2) = 2.156, p = 0.024] that suggested a small and significant association between MVPA and SWL (p = 0.032). A significant multivariate analysis of variance (MANOVA) [Wilks’ λ = 0.945, F(3159) = 3.1, p = 0.028] suggested participants meeting guidelines reported significantly fewer anxiety symptoms (Mdiff = −1.23, p = 0.027) and higher perceptions of SWL (Mdiff = 3.0, p = 0.008). No significant associations emerged for sedentary time [Wilks’ λ = 0.956, F(9382.3) = 0.788, p = 0.628].ConclusionsContrary to previously published research using self-reports, objectively assessed MVPA and sedentary time were not associated with depression symptoms. Objectively assessed MVPA was associated with SWL and anxiety outcomes in colon cancer survivors.Implications for Cancer SurvivorsColon cancer survivors should continue to engage in regular and sustained MVPA for the accrual of psychological health benefits.

Tea, Coffee, and Milk Consumption and Colorectal Cancer Risk

Background Data regarding the effects of tea, coffee, and milk on the risk of colorectal cancer are inconsistent. We investigated associations of tea, coffee, and milk consumption with colorectal cancer risk and attempted to determine if these exposures were differentially associated with the risks of proximal colon, distal colon, and rectal cancers. Methods Data from 854 incident cases and 948 controls were analyzed in a case-control study of colorectal cancer in Western Australia during 2005–07. Multivariable logistic regression was used to analyze the associations of black tea (with and without milk), green tea, herbal tea, hot coffee, iced coffee, and milk with colorectal cancer. Results Consumption of 1 or more cups of herbal tea per week was associated with a significantly decreased risk of distal colon cancer (adjusted odds ratio, 0.37; 95% CI, 0.16–0.82; PTrend = 0.044), and consumption of 1 or more cups of iced coffee per week was associated with increased risk of rectal cancer (adjusted odds ratio, 1.52; 95% CI, 0.91–2.54; PTrend = 0.004). Neither herbal tea nor iced coffee was associated with the risk of proximal colon cancer. Hot coffee was associated with a possible increased risk of distal colon cancer. Black tea (with or without milk), green tea, decaffeinated coffee, and milk were not significantly associated with colorectal cancer risk. Conclusions Consumption of herbal tea was associated with reduced risk of distal colon cancer, and consumption of iced coffee was associated with increased rectal cancer risk.

Meat consumption and cooking practices and the risk of colorectal cancer

Background/Objectives:The association between meat consumption and the risk of colorectal cancer (CRC) has been controversial. One of the difficulties in determining this association has been measurement of different attributes of meat consumption, including cooking methods and level of doneness.Subjects/Methods:We investigated the association between meat consumption and cooking practices and the risk of CRC in a population-based case–control study in the Western Australian Bowel Health Study. From July 2005 to February 2007, 567 incident CRC cases and 713 controls, who were frequency matched to cases for age- and sex, completed questionnaires on lifestyle and meat consumption. Estimated odds ratios (ORs) comparing meat consumption quartile groups were obtained from multivariate logistic regression models.Results:The amount of red baked meat consumed had a statistically significant inverse trend of association with CRC (Q4 OR=0.73 95% confidence interval 0.53–1.01). When frequency was multiplied by serving size and by doneness, the association remained protective but was no longer statistically significant. The protective trends for red pan-fried meat were also borderline statistically significant. There were no other statistically significant or meaningful associations with any of the types of meat cooked by any method and the risk of CRC.Conclusions:Our data do not support the hypothesis that meat consumption is a risk factor for CRC.