Sedentary jobs and colon cancer

Walking time, sports activity, job type, and body posture during work in relation to incident colorectal cancer: the JACC prospective cohort study

PURPOSE

An inverse association between physical activity and colorectal cancer (CRC) has been suggested. We aimed to assess the specific and combined effects of leisure-time and occupational physical activities on CRC risk among Japanese adults.

METHODS

Using Cox proportional hazard models, we tested whether walking time, sports activity, body posture during work, and job type-or the combination of these variables-were associated with CRC incidence in a prospective cohort of 26,897 Japanese adults aged 40-79 years.

RESULTS

During a median 17-year follow-up (1990-2009) period, we ascertained 423 incident cases of CRC (267 colon and 156 rectum cancer). Time spent walking suggested a dose-response inverse relationship with CRC risk (p-trend = 0.051). Manual labor was associated with lower CRC risk when compared to office work with HRs (95% CIs) of 0.74 (0.56-0.97) for CRC and 0.68 (0.48-0.96) for colon cancer. Compared to sitting, moving during work tended to be inversely associated with rectal cancer risk, especially after censoring early incident cases within 3 years after baseline; HR (95% CI) = 0.63 (0.40-0.99). Combining walking and job type suggested mutual and synergistic benefits on the risk of colon cancer (p-interaction = 0.03). Compared to office workers walking < 1 h/day, the HR (95% CI) of colon cancer was 0.48 (0.23-0.98), 0.61 (0.42-0.89), and 0.59 (0.41-0.87) in office workers walking ≥ 1 h/day, non-office workers walking < 1 h/day, and non-office workers walking ≥ 1 h/day, respectively.

CONCLUSION

The time spent walking, job type, and posture during work were independently associated with the reduced incident CRC risk among Japanese men and women.

The associations of sitting time and physical activity on total and site-specific cancer incidence: Results from the HUNT study, Norway

Background

Sedentary behavior is thought to pose different risks to those attributable to physical inactivity. However, few studies have examined the association between physical activity and sitting time with cancer incidence within the same population.

Methods

We followed 38,154 healthy Norwegian adults in the Nord-Trøndelag Health Study (HUNT) for cancer incidence from 1995–97 to 2014. Cox proportional hazards regression was used to estimate risk of site-specific and total cancer incidence by baseline sitting time and physical activity.

Results

During the 16-years follow-up, 4,196 (11%) persons were diagnosed with cancer. We found no evidence that people who had prolonged sitting per day or had low levels of physical activity had an increased risk of total cancer incidence, compared to those who had low sitting time and were physically active. In the multivariate model, sitting ≥8 h/day was associated with 22% (95% CI, 1.05–1.42) higher risk of prostate cancer compared to sitting <8 h/day. Further, men with low physical activity (≤8.3 MET-h/week) had 31% (95% CI, 1.00–1.70) increased risk of colorectal cancer (CRC) and 45% (95% CI, 1.01–2.09) increased risk of lung cancer compared to participants with a high physical activity (>16.6 MET-h/week). The joint effects of physical activity and sitting time the indicated that prolonged sitting time increased the risk of CRC independent of physical activity in men.

Conclusions

Our findings suggest that prolonged sitting and low physical activity are positively associated with colorectal-, prostate- and lung cancer among men. Sitting time and physical activity were not associated with cancer incidence among women. The findings emphasizing the importance of reducing sitting time and increasing physical activity.

Domain-specific physical activity and sedentary behaviour in relation to colon and rectal cancer risk: a systematic review and meta-analysis

Background

Physical activity is associated with reduced risk of colorectal cancer, but most epidemiological studies have focused on occupational and recreational physical activity. The evidence for other domains of activity, and for sedentary behaviour, is limited.

Methods

Medline, Embase and Web of Science were searched from inception to December 2015 for studies examining domain-specific physical activity or sedentary behaviour and the risk of colon and/or rectal cancer. We extracted maximally adjusted relative risks (RRs) except when RRs not adjusted for body mass index, were also presented. We used random-effects meta-analysis to compute pooled RRs comparing the highest versus the lowest level of exposure. We used meta-regression to assess sources of heterogeneity in estimates.

Results

We identified 17 cohort and 21 case-control studies, of which 17 had occupational data, 23 had recreational data, three each had data on transport and household physical activity domains, and 6 studies had data on occupational sedentary behaviour. The pooled relative risks (RRs) for colon cancer were 0.74 (95% confidence interval (CI): 0.67, 0.82) for occupational activity, 0.80 (95% CI: 0.71, 0.89) for recreational activity, 0.66 (95% CI: 0.45, 0.98) for transport-related physical activity, 0.85 (95% CI: 0.71, 1.02) for household physical activity, and 1.44 (95% CI: 1.28, 1.62) for occupational sedentary behaviour. For rectal cancer, the pooled RRs were 0.88 (95% CI: 0.79, 0.98) for occupational activity, 0.87 (95% CI: 0.75, 1.01) for recreational activity, 0.88 (95% CI: 0.70, 1.12) for transport-related physical activity, 1.01 (95% CI: 0.80, 1.27) for household physical activity, and 1.02 (95% CI: 0.82, 1.28) for occupational sedentary behaviour.

Conclusions

In addition to increasing occupational and recreational physical activity, promoting physical activity during transport and reducing sedentary behaviour in the workplace may also be useful colorectal cancer prevention strategies.

Asbetos Exposure, Physical Activity and Colon Cancer: A Case-Control Study

Aims and Background

An association between colon cancer and the occupation of model or pattern maker in the car industry has been repeatedly suggested. The aim of our study was to investigate colon cancer and occupational exposures (in particular in the car industry) in an industrialized area of northern Italy.

Methods

We conducted a hospital-based case-referent study on colon cancer (n = 131; hospital controls, n = 463). All subjects were interviewed, and jobs in the car industry were investigated. Occupational exposure to asbestos and the level of physical activity were blindly assessed. All the jobs were classified according to energy expenditure (less than 8, 8-12 and more than 12 kJ/min).

Results

We found no association between colon cancer and any job in the car industry. No subject had worked as a model or pattern maker. Sedentary work was associated with colon cancer in men but not in women. An excess risk was demonstrated among males for job titles involving putative exposure to asbestos (4 cases and 3 controls; OR = 4.8, 95 % c.i. 1.05-21.5), in particular pipe fitters and boilermakers (3 cases and 1 control; OR = 10.7; 1.07-103).

Daily sedentary time and its association with risk for colorectal cancer in adults: A dose-response meta-analysis of prospective cohort studies

Sedentary behavior is emerging as an independent risk factor for health. However, previous studies have indicated that sedentary behaviors are associated with the colorectal cancer risk, but presented controversial results.Studies in PubMed and EMBASE were searched update to February 2017 to identify and quantify the potential dose-response association between daily sedentary time and colorectal cancer.Twenty-eight eligible studies involving a total of 47,84,339 participants with 46,071 incident cases were included in this meta-analysis. Our results showed statistically significant association between prolong television viewing time and colorectal cancer (odds ratio [OR] 1.17, 95% confidence interval [CI] 1.09-1.24, P < .001). Additionally, we obtained the best fit at an inflection point of 2 hours per day in piecewise regression analysis, the summary relative risk (RR) of colorectal cancer for an increase of 2 hours per day television viewing was 1.07 (95% CI 1.05-1.10, P < .001). Furthermore, prolong occupational sitting time was correlated with a significantly higher risk of colorectal cancer (OR 1.15, 95% CI 1.08-1.22, P < .001), increasing 2 hours per day of occupational sitting time per day was associated with a 4% incremental in the risk of colorectal cancer (RR 1.04, 95% CI 1.01-1.08). Additionally, prolong total sitting time was associated with a significantly higher risk of colorectal cancer (OR 1.06, 95% CI 1.03-1.09, P < .001). Increasing 2 hours of total sitting time per day was associated with a 2% incremental in the risk of colorectal cancer (RR 1.02, 95% CI 1.01-1.06). Subgroup meta-analyses in study design, study quality, number of participants, and number of cases showed consistent with the primary findings.Prolonged television viewing, occupational sitting time, and total sitting time are associated with increased risks of colorectal cancer.

Association Between Sedentary Work and BMI in a U.S. National Longitudinal Survey

INTRODUCTION

Technological advancements have made life and work more sedentary, and long hours of sitting are known to be associated with many health concerns. Several studies have reported an association between prolonged sitting time at work and weight gain, but the results are inconsistent. This study examined the relationship between sitting time at work and BMI using data from a large prospective cohort of U.S. men and women from 2002 to 2010. Initial analyses were performed in 2013, with additional analyses in 2014 and 2015.

METHODS

The sample size at the base year (2002) was 5,285 and the age range 38-45 years. The outcome, BMI, was based on self-reported measures of height and weight. Estimates of workplace sitting time were linked from an external database (Occupational Information Network), and the occupation-wide rating for sitting time was linked to survey participants by occupation. Fixed-effects models controlling for time-invariant effects of all time-invariant characteristics were employed to examine the association, controlling for age, education, work hours, and hours of vigorous and light/moderate physical activities.

RESULTS

Longer sitting time was significantly associated with higher BMI for the overall sample (β = 0.054; p<0.05) and men (β = 0.086; p<0.01). For women, the association was not statistically significant.

CONCLUSIONS

The findings provide further support for initiatives to reduce workplace sitting time as a means of reducing the risk of weight gain and related health conditions.

Television watching and risk of colorectal adenoma

Background:

Prolonged TV watching, a major sedentary behaviour, is associated with increased risk of obesity and diabetes and may involve in colorectal carcinogenesis.

Methods:

We conducted a cross-sectional analysis among 31 065 men with ⩾1 endoscopy in the Health Professionals Follow-up Study (1988–2008) to evaluate sitting while watching TV and its joint influence with leisure-time physical activity on risk of colorectal adenoma. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

Results:

Prolonged sitting while watching TV was significantly associated with increased risk of colorectal adenoma (n=4280), and adjusting for physical activity or a potential mediator body mass index did not change the estimates. The ORs (95% CIs) across categories of TV watching (0–6, 7–13, 14–20, and 21+ h per week) were 1.00 (referent), 1.09 (1.01–1.17), 1.16 (1.06–1.27), and 1.10 (0.97–1.25) (OR per 14-h per week increment=1.11; 95% CI: 1.04–1.18; P_trend=0.001). Compared with the least sedentary (0–6 h per week of TV) and most physically active (highest quintile) men, the most sedentary (14+ h per week) and least active (lowest quintile) men had a significant increased risk of adenoma (OR=1.25; 95% CI: 1.05–1.49), particularly for high-risk adenoma.

Conclusions:

Prolonged TV viewing is associated with modest increased risk of colorectal adenoma independent of leisure-time physical activity and minimally mediated by obesity.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Association of sedentary behaviour with colon and rectal cancer: a meta-analysis of observational studies

BACKGROUND

Sedentary behaviour is ubiquitous in modern society. Emerging studies have focused on the health consequences of sedentary behaviour, including colorectal cancer, but whether sedentary behaviour is associated with the risks of colon and rectal cancer remains unclear. No systematic reviews have applied quantitative techniques to independently compute summary risk estimates. We aimed to conduct a meta-analysis to investigate this issue.

METHODS

We searched PubMed, Embase, and Google Scholar databases up to May 2013 to identify cohort and case-control studies that evaluated the association between sedentary behaviour and colon or rectal cancer. A random-effect model was used to pool the results of included studies. Publication bias was assessed by using Begg's funnel plot.

RESULTS

Twenty-three studies with 63 reports were included in our meta-analysis. These groups included 4,324,462 participants (27,231 colon cancer cases and 13,813 rectal cancer cases). Sedentary behaviour was significantly associated with colon cancer (relative risk (RR): 1.30, 95% confidence interval (CI): 1.22-1.39) but did not have a statistically significant association with rectal cancer (RR 1.05, 95% CI, 0.98-1.13). Subgroup analyses suggested that the odds ratio (OR) of colon cancer was 1.46 (95% CI: 1.22-1.68) in the case-control studies, and the RR was 1.27 (95% CI: 1.18-1.36) in the cohort studies, the OR of rectal cancer was 1.06 (95% CI: 0.85-1.33) in the case-control studies, and the RR was 1.06 (95% CI, 1.01-1.12) in the cohort studies.

CONCLUSION

Sedentary behaviour is associated with an increased risk of colon cancer. Subgroup analyses suggest a positive association between sedentary behaviour and risk of rectal cancer in cohort studies. Reducing sedentary behaviour is potentially important for the prevention of colorectal cancer.

Physical Activity and Colon Cancer

Despite the convincing evidence that physical activity reduces the risk of colon cancer, there are some aspects of the association that remain unclear. These include the appropriate timeframe of exposure, whether the intensity of physical activity matters, and whether sedentary behavior is a distinct risk factor. This review summarized the research that has investigated these issues. In terms of timing, physical activity at any age (with the exception of physical activity performed up to and including the late teens) has been shown to be associated with a significantly reduced risk of colon cancer. Physical activity performed between 30 and 50 years of age, as well as long-term or lifetime physical activity, has been most consistently shown to reduce risk. For intensity, research to date suggests that more intense activity (particularly vigorous activity) may be associated with a greater reduction in the risk of colon cancer for males but not for females. Finally, most of the studies that have investigated the effect of sedentary behavior on the risk of colon or colorectal cancer have shown an increased risk, suggesting that sedentary behavior may be a distinct risk factor for colon cancer.

Nuclear factor-erythroid 2-related factor 2 as a chemopreventive target in colorectal cancer

INTRODUCTION

Numerous epidemiological studies have linked consumption of cruciferous vegetables to a reduced risk of colorectal cancer (CRC) in individuals. It is currently well accepted that chronic inflammation is a contributing factor in 15 - 20% malignancies including CRC. Many chemopreventive compounds are effective in preclinical systems and many ongoing clinical trials are showing promising findings. Many of these compounds could activate the antioxidant responsive element (ARE), a critical regulatory element for Phase II protective/detoxification and antioxidative stress enzymes mediated by nuclear factor-erythroid 2-related factor 2 (Nrf2). Recently, Nrf2 has emerged as a novel target for the prevention of CRC.

AREAS COVERED

A full literature search was performed using PubMed with the key words 'ARE, Nrf2, colon, colorectal cancer, chemoprevention, cancer prevention', and all relevant publications are included.

EXPERT OPINION

The use of Nrf2 knockout mice has provided key insights into the toxicological and chemopreventive importance of this pathway. Mounting evidence has revealed that Nrf2 is a critical regulator of inflammation as well, a major driving force for CRC progression and formation. Targeting the Nrf2/ARE pathway may present a novel therapeutic approach for the treatment of not only colorectal inflammatory diseases but the frequent subsequent development of CRC as well.

Trends in colorectal cancer incidence in Norway 1962-2006: an interpretation of the temporal patterns by anatomic subsite

There have been rapid increases in the incidence of colorectal cancer in Norway since the 1960s, and rates rank among the highest worldwide. The primary objectives are to describe trends in left- and right-sided colon cancer and rectal cancer by calendar period and birth cohort and to generate hypotheses as to the etiological factors in operation. Although the age-adjusted incidence rates of both colon and rectal cancer increased in Norway in both sexes up to the 1980s, subsite- and age-specific analyses reveal a deceleration in the rate of increase thereafter, apparent in the rates of both left-sided colon and rectal cancer. Overall trends in incidence of right-sided colon cancer continue to increase in both sexes. Rates in both left- and right-sided colon cancers have tended to stabilize or decrease among successive generations born after 1950, however, while incidence rates of rectal cancer appear to be increasing in recent generations. The all-ages rates are thus in keeping with the commonly reported "left to right shift" of colon cancer, although standardization masks important observations. The cohort patterns provide further evidence that factors earlier in life are important, and while the complex etiology makes interpretation difficult, modifications in diet, obesity and physical activity in Norway are likely among the drivers of the trends in one or more of the colorectal subsites examined. In summary, the recent downturn in the disease at younger ages provides some reason for optimism, although possible increases in rectal cancer among recent birth cohorts are of concern.

Physical activity and gastrointestinal cancer prevention

Colorectal cancer is the third most common cancer globally and is a leading cause of cancer death. Gastric cancer contributes significantly to the global cancer burden, particularly in low- and middle-income countries. We reviewed the literature for studies on physical activity or exercise and colon, rectal, and gastric cancers as well as colonic adenomatous polyps. We identified 52 studies of colon cancer, 31 studies of rectal cancer, 23 studies of colon polyps, and 16 studies of gastric cancer. Of the 52 studies of physical activity and colon cancer, 37 found a statistically significant association between increased levels of physical activity and decreased colon cancer risk in at least one comparison. Accumulated evidence suggests that physical activity is associated with a 25% reduction in colon cancer risk. In line with previous reports, we found no indication that the association was more pronounced for occupational versus recreational physical activity, with both resulting in a risk reduction of about 22%. Evidence for other domains of physical activity (i.e., transportation or household physical activity) is limited. Evidence is emerging that individuals who are consistently active across the lifetime may obtain greater risk reductions than those who are only active in recent years. Despite consistent associations with colon cancer, evidence is more limited though suggestive that physical activity reduces risk of colon adenomas or adenoma recurrence. There is clear evidence that physical activity is not associated with rectal or gastric cancers.

Occupational physical activity and risk of malignant melanoma: the Western Canada Melanoma Study

The relationship between physical activity and cutaneous malignant melanoma has not been fully investigated; in particular, many previous studies have not controlled for sunlight exposure, which is an important environmental risk factor for melanoma. The aim of this study was to examine the relationship between occupational physical activity and melanoma risk. The data were collected for a population-based case-control study that consisted of 595 melanoma patients diagnosed between 1979 and 1981. Five hundred and ninety-five controls matched on sex, age and area of residence were selected from provincial government health insurance rolls. Lifetime job histories, sun exposure and other host factors were obtained from personal interviews with each individual. Logistic regression analysis was used to examine the relationship between melanoma risk and occupational activity levels, measured as total metabolic equivalent hours, with adjustment for occupational sun exposure, recreational sun exposure and host factors. Risk estimates were elevated above one for each occupational activity quintile compared with those with sedentary jobs. However, the pattern of risk ratios was irregular and statistical significance was reached only by the highest quintile (odds ratio: 1.59, 95% confidence interval: 1.02-2.47) and the second lowest quintile (odds ratio: 1.62, 95% confidence interval: 1.10-2.39). Our data showed an elevated risk for cutaneous malignant melanoma among those with higher levels of physical activity, although no clear dose-response relationship was observed. Further studies examining lifetime physical activity histories and sunlight exposure are required to explicate these findings.

Physical activity, obesity and risk for esophageal adenocarcinoma

Over the past three decades, an increasing incidence of esophageal adenocarcinoma (EADC) has been reported throughout North America and Europe at a rate exceeding that of any other human solid tumor. Recent studies have clearly implicated chronic gastroesophageal reflux disease and several lifestyle risk factors, including tobacco consumption, diet and obesity, to be associated with increased risk of EADC. Although physical inactivity is now recognized as a risk factor for several chronic diseases including cancer, only a very limited number of studies have specifically evaluated the association between physical activity and esophageal malignancy. Furthermore, the precise biological mechanisms underlying the association between physical activity, obesity and cancer risk remain unclear. Since successful promotion of healthy body weight and exercise may substantially reduce the future incidence of cancer in the population, the purpose of this review is to explore current evidence linking physical activity, obesity and risk of malignancy – specifically EADC.

Lifestyle factors and colorectal cancer risk (2): a systematic review and meta-analysis of associations with leisure-time physical activity

OBJECTIVE

Increased physical activity may decrease the risk of colorectal cancer. As a prerequisite to the determination of lifestyle attributable risks, we performed a systematic review and meta-analysis of prospective observational studies to quantify gender-specific risk associated with increased leisure-time physical activity (LT-PA).

METHOD

We searched MEDLINE and EMBASE (to December 2007), and other sources, selecting reports based on strict inclusion criteria. We used random-effects meta-analyses to estimate summary risk ratios (RR) and 95% confidence intervals (95% CI) for uppermost vs lowermost categories of physical activity. To investigate dose-response, we explored risks ratios as a function of cumulative percentiles of physical activity distribution.

RESULTS

Fifteen datasets from 14 articles, including 7873 incident cases, were identified. For colon cancer, there were inverse associations with LT-PA for men (RR: 0.80; 95% CI: 0.67-0.96) and women (0.86; 0.76-0.98). LT-PA did not influence risk of rectal cancer. The dose-response analysis was consistent with linear pattern reductions in risk of colon cancer in both genders. There was evidence of moderate between-study heterogeneity but summary estimates were broadly consistent across potential confounding factors.

CONCLUSION

Increased LT-PA is associated with a modest reduction in colon but not rectal cancer risk; a risk reduction, which previously may have been overstated. LT-PA only interventions in public health cancer prevention strategies are unlikely to impact substantially on colorectal cancer incidences.

Physical activity and colon cancer prevention: a meta-analysis

Although an inverse association between physical activity and risk of colon cancer is well established, a formal estimate of the magnitude of this risk reduction that includes recent studies is not available. This analysis examines the association by sex and study design, restricting analyses to studies where data for colon cancer alone were available. The authors reviewed published studies through June 2008 examining the association between physical activity and risk of colon cancer. Heterogeneity and publication bias were evaluated and random effects models used to estimate relative risks (RR). Differences by sex and study design were evaluated. A total of 52 studies were included. An inverse association between physical activity and colon cancer was found with an overall relative risk (RR) of 0.76 (95% confidence interval (CI): 0.72, 0.81). For men, the RR was 0.76 (95% CI: 0.71, 0.82); for women, this was little different, (RR=0.79, 95% CI: 0.71, 0.88). The findings from case-control studies were stronger (RR=0.69, 95% CI: 0.65, 0.74) than for cohort studies (RR=0.83, 95% CI: 0.78, 0.88). This study confirms previous studies reporting an inverse association between physical activity and colon cancer in both men and women, and provides quantitative estimates of the inverse association.

Occupational physical activity and risk for cancer of the colon and rectum in Sweden among men and women by anatomic subsite

Inverse association between physical activity and colon cancer is well established, at least in men. We investigated the association of occupational physical activity with subsite-specific colorectal cancer risk. On the basis of occupational titles from the Swedish nationwide censuses in 1960 and 1970, we defined a cohort of women and men with the same work-related physical demands in 1960 and 1970. Incidence of colon and rectum cancer during 1971-1989 was ascertained through linkages to the Cancer Register. Relative risks (RRs) were estimated through Poisson regression. The risk for colon cancer increased with decreasing occupational physical activity. RR among sedentary women and men was 1.2 and 1.3 (P for trend=0.08 and <0.001). For men, the risks for proximal and distal colon cancer increased by 20 and 40% (P for trend=0.005 and <0.001). Inactivity seemed to be particularly associated with descending colon cancer (RR =2.4, P for trend<0.001). In women, the inverse association with activity was concentrated to proximal parts of colon; RR for cancer in the proximal and transverse colon among sedentary women was 1.4 and 2.0 (P for trend <0.07 and <0.01). Cancer of the rectum was not associated with activity in either sex. We confirmed the well-known inverse relationship between activity and risk of colon cancer but not rectal cancer in both sexes. Data suggest that the physical activity-related variation in risk among women is greatest in the proximal and middle parts of the colon, whereas the corresponding peak in men seems to be more distal. Sex-specific anatomic and motility differences of the colon might contribute to this subsite difference.

Physical activity, sedentary behavior, and the risk of colon and rectal cancer in the NIH-AARP Diet and Health Study

OBJECTIVE

In order to prospectively investigate physical activity at varying intensities and sedentary behavior in relation to colorectal cancer.

METHODS

We considered 488,720 participants of the NIH-AARP Diet and Health Study who were aged 50-71 years at baseline in 1995-1996. Through 31 December, 2003, we identified 3,240 and 1,482 colorectal cancers among men and women, respectively. We estimated multivariable relative risks (RR) and 95% confidence intervals (CI) of colorectal cancer using Cox regression.

RESULTS

Engaging in exercise/sports five or more times per week compared to never or rarely exercising was associated with a reduced risk of colon cancer among men (p = 0.001; RR = 0.79, 95% CI = 0.68-0.91) and a suggestive decrease in risk among women (p = 0.376; RR = 0.85, 95% CI = 0.70-1.04). Engaging in exercise/sports was also associated with a decreased risk of rectal cancer in men (P = 0.074; RR comparing extreme categories = 0.76, 95% CI = 0.61-0.94). In men, we observed inverse relations of both low intensity (p = 0.017; RR = 0.81, 95% CI = 0.65-1.00 for > or =7 h/week) and moderate to vigorous intensity activity (p = 0.037; RR = 0.82, 95% CI = 0.67-0.99 for > or =7 h/week) to colon cancer risk. In contrast, sedentary behavior (time spent watching television/videos) was positively associated with colon cancer (p < 0.001; RR = 1.61, 95% CI = 1.14-2.27 for > or =9 h/day) among men. Similar, but less pronounced relations were observed in women.

CONCLUSION

Engaging in physical activity of any intensity is associated with reductions in colon and rectal cancer risk. Conversely, time spent sedentary is associated with increased colon cancer risk.

Recreational physical activity and cancer risk in subsites of the colon (the Nord-Trøndelag Health Study)

Physical activity may reduce colon cancer risk, but the underlying mechanisms remain unclear. Relating physical activity to cancer risk in anatomic segments of the colon may advance our understanding of possible mechanisms. We conducted a prospective study of 59,369 Norwegian men and women who were followed up for cancer incidence and mortality. Cox proportional hazards models were used to estimate multivariably adjusted hazard ratios (HR) and 95% confidence intervals (95% CI). All statistical tests were two sided. During 17 years of follow-up, 736 colon cancers and 294 rectal cancers were diagnosed. Overall, we found an inverse association between recreational physical activity and colon cancer risk, but subsite analyses showed that the association was confined to cancer in the transverse and sigmoid colon. The adjusted HR, comparing people who reported high versus no physical activity, was 0.44 (95% CI, 0.25-0.78) for cancer in the transverse colon and 0.48 (95% CI, 0.31-0.75) for cancer in the sigmoid colon. The corresponding HR for cancer mortality was 0.33 (95% CI, 0.14-0.76) for the transverse colon and 0.29 (95% CI, 0.15-0.56) for the sigmoid colon. For rectal cancer, there was no association with physical activity in these data. In conclusion, the inverse association of recreational physical activity with cancer risk and mortality in the transverse and sigmoid segments of the colon may point at increased colon motility and reduced fecal transit time as possible underlying mechanisms.

Validity and reliability of self-reported total energy expenditure using a novel instrument

Improved methods for quantitative self-reports of total physical activity in epidemiological studies are needed. We evaluated randomly selected individuals' ability to integrate their perception of physical activity over time to produce an estimate of the "usual" level, using a novel instrument for self-quantification of energy expenditure. A population-based sample of 418 Swedish men and women, age 20-59, completed a questionnaire containing the new instrument. For validation, three 24 hour recalls by phone served as gold standard. Reproducibility was assessed through administering the instrument another three times. The validation involved 133 subjects and another 160 completed the reproducibility evaluation. Pearson correlation between usual daily energy expenditure measured by the instrument and the mean of the 24 hour recalls was 0.73. After subdividing the self-reported daily energy expenditure and the mean of the 24 hour recalls into quintiles, 83.5% of the participants remained in the same quintile, or one quintile apart. There was a tendency towards overestimation of usual daily physical activity. This was significantly associated with low education. Reproducibility showed an intraclass correlation of 0.55. Although integrated reports of usual daily energy expenditure over longer periods seem to be afflicted with a tendency of overestimation, total energy expenditure can be estimated with reasonable validity and reproducibility using our instrument.

Physical activity and risk of colon and rectal cancers: the European prospective investigation into cancer and nutrition

We investigated several aspects of the role of physical activity in colon and rectal cancer etiology that remain unclear in the European Prospective Investigation into Nutrition and Cancer. This cohort of 413,044 men and women had 1,094 cases of colon and 599 cases of rectal cancer diagnosed during an average of 6.4 years of follow-up. We analyzed baseline data on occupational, household, and recreational activity to examine associations by type of activity, tumor subsite, body mass index (BMI), and energy intake. The multivariate hazard ratio for colon cancer was 0.78 [95% confidence interval (95% CI), 0.59-1.03] among the most active participants when compared with the inactive, with evidence of a dose-response effect (P(trend) = 0.04). For right-sided colon tumors, the risk was 0.65 (95% CI, 0.43-1.00) in the highest quartile of activity with evidence of a linear trend (P(trend) = 0.004). Active participants with a BMI under 25 had a risk of 0.63 (95% CI, 0.39-1.01) for colon cancer compared with the inactive. Finally, an interaction between BMI and activity (P(interaction) = 0.03) was observed for right-sided colon cancers; among moderately active and active participants with a BMI under 25, a risk of 0.38 (95% CI, 0.21-0.68) was found as compared with inactive participants with BMI >30. No comparable decreased risks were observed for rectal cancer for any type of physical activity for any subgroup analyses or interactions considered. We found that physical activity reduced colon cancer risk, specifically for right-sided tumors and for lean participants, but not rectal cancer.

Physical activity and risk of colon cancer in a cohort of Danish middle-aged men and women

OBJECTIVE

To investigate the effects of occupational activity and leisure time activity on incident colon cancer risk in a Danish middle-aged population.

METHODS

In the cohort, Diet, Cancer and Health, which included 28,356 women and 26,122 men aged 50-64 years at baseline, 140 women and 157 men were diagnosed with colon cancer from 1993 to 2003. The associations between occupational and leisure time activity in terms of a MET-score and the single activities, sports, cycling, walking, gardening, housework and do-it-yourself work, and incident colon cancer were investigated. Leisure time activity was investigated in two ways using the Cox proportional hazards model: by comparison of active versus non-active and by investigating a possible dose-response relationship while allowing a separate association for non-active individuals.

RESULTS

No associations were found between risk of colon cancer and occupational activity, MET-hours per week of total leisure time activity, residuals from a regression of each activity on the total MET-hours or the time spent on any of the six types of leisure time activities. However, a borderline significant association was found with the number of activities in which the participants were active. For each additional activity IRR = 0.87 (0.76-1.00) for women and IRR = 0.88 (0.78-1.00) for men.

CONCLUSION

Our data do not support the evidence of an inverse association between colon cancer risk and occupational activity or leisure time activity, but avoiding a sedentary lifestyle by participating in different activities may reduce colon cancer risk.

Physical activity and colorectal cancer: the Fukuoka Colorectal Cancer Study

The number of cases of colorectal cancer in Japan has increased over the past few decades, and incidence rates are now among the highest in the world. The present investigation within the Fukuoka Colorectal Cancer Study, including 778 cases and 767 controls aged 20-74 years, examined the association between physical activity and colorectal cancer risk by subsite. Employment-associated and leisure time physical activity was assessed by a questionnaire and interview. Division of sites into the proximal and distal colon, as well as the rectum, revealed clear site-dependent protective effects, with adjustment for smoking, alcohol consumption, BMI and age. In males, greater job-related physical activity was associated with significant reduction of risk in the distal colon and rectum (P = 0.047 and 0.02, respectively), whereas total and moderate or hard non-job physical activity exerted effects limited to the rectum (P = 0.01 and 0.004, respectively). In females, job-related physical activity and moderate or hard non-job physical activity was also protective, but only in the distal colon. Separate assessment of the influence of BMI 10 years previous to the study showed increase in risk with obesity in males but not in females, limited to distal colon and rectum. The results of the present study indicate that physical activity associated with work and leisure-time exerts beneficial effects in Japanese, but not on the proximal colon.

Occupational and leisure-time physical activity and risk of colon cancer by subsite

OBJECTIVE

Studies of physical activity and colon cancer risk by anatomic site have provided inconsistent results.

METHODS

We analyzed data from a population-based case-control study conducted in Iowa involving 685 colon cancer cases and 2434 control subjects.

RESULTS

Among those who reported recreational activity more than twice per week, a 30% risk reduction of colon cancer was observed for all sites with a 40% risk reduction for cancer of the right colon. Occupational physical activity was also associated with a reduced risk of colon cancer. The risk was the lowest for those with both high occupational and recreational physical activity (odds ratio, 0.5; 95% confidence interval, 0.3-0.8).

CONCLUSIONS

Increased physical activity was inversely associated with colon cancer risk. The inverse associations were stronger for the right than for the left colon.

Case–control study of lifetime occupational and recreational physical activity and risks of colon and rectal cancer

Important aspects of the inverse relation between physical activity and colon cancer risk are still under discussion. In 2000-2003, 239 incident cases of colorectal cancer confirmed by histopathology and 239 hospital-based controls, matched by age and gender, were enrolled. In standardized interviews, data on occupational and recreational physical activity for ages 20, 30, 40, 50 and 60 years were collected from 98 colon cancer cases, 141 rectal cancer cases, and from 193 controls. Besides lifestyle and sociodemographic characteristics, a detailed food frequency questionnaire was assessed. In multivariate logistic regression for colon cancer, significant risk reductions for the highest quartile of total physical activity were found for almost all ages. For lifetime mean physical activity, the multivariate odds ratio for the highest quartile was 0.37 [95% confidence interval (CI) 0.17, 0.83]. For lifelong constantly high-exercisers compared with lifelong non-exercisers an odds ratio of 0.26 (95% CI 0.08, 0.84) was estimated. For rectal cancer, no consistent association with physical activity was found. No confounding effects were observed but the authors found effect modification with total energy intake. These data support an inverse association of colon cancer risk and physical activity which is most expressed if activity is kept up throughout life.

A meta-analysis of the association of physical activity with reduced risk of colorectal cancer

BACKGROUND

Physical activity may be associated with reduced risk of colorectal cancer. The main aim of this paper is to review the available evidence for a link between exercise and large bowel cancer.

METHODS

A Cochrane-type methodology was performed. Data extracted included, type of study, type of physical activity measured and the numerical results. The risk ratios (RR) of the studies have been pooled according to the type of study, type of exercise, type of cancer and sex. Pooling was undertaken using fixed effect meta-analysis. A random effect meta-analysis was used where substantial heterogeneity existed.

RESULT

Data from 19 cohort studies showed a statistically significant reduction in the risk of colon cancer in physically active males, RR being 0.79 (95% CI 0.72-0.87) and 0.78 (95% CI 0.68-0.91) for occupational and recreational activities, respectively. In women only recreational activities are protective against colon cancer (RR = 0.71, 95%CI 0.57-0.88). Case-control studies showed significantly reduced risks of colon cancer in both sexes irrespective of the type of activity. No protection against rectal cancer is seen in either sex.

CONCLUSION

There is considerable evidence that physical activity is associated with reduced risk of colon cancer in both males and females.

Primary prevention of colorectal cancer: lifestyle, nutrition, exercise

The past two decades have provided a vast amount of literature related to the primary prevention of colorectal cancer. Large international variation in colorectal cancer incidence and mortality rates and the prominent increases in the incidence of colorectal cancer in groups that migrated from low- to high-incidence areas provided important evidence that lifestyle factors influence the development of this malignancy. Moreover, there is convincing evidence from epidemiological and experimental studies that dietary intake is an important etiological factor in colorectal neoplasia. Although the precise mechanisms have not been clarified, several lifestyle factors are likely to have a major impact on colorectal cancer development. Physical inactivity and to a lesser extent, excess body weight, are consistent risk factors for colon cancer. Exposure to tobacco products early in life is associated with a higher risk of developing colorectal neoplasia. Diet and nutritional factors are also clearly important. Diets high in red and processed meat increase risk. Excess alcohol consumption, probably in combination with a diet low in some micronutrients such as folate and methionine, appear to increase risk. There is also recent evidence supporting a protective effect of calcium and vitamin D in the etiology of colorectal neoplasia. The relationship between intake of dietary fiber and risk of colon cancer has been studied for three decades but the results are still inconclusive. However, some micronutrients or phytochemicals in fiber-rich foods may be important; folic acid is one such micronutrient that has been shown to protect against the development of colorectal neoplasia and is currently being studied in intervention trials of adenoma recurrence. The overwhelming evidence indicates that primary prevention of colon cancer is feasible. Continued focus on primary prevention of colorectal cancer, in combination with efforts aimed at screening and surveillance, will be vital in attaining the greatest possible progress against this complex, yet highly preventable disease.

The Economic Costs Associated With Physical Inactivity and Obesity in Canada: An Update

The purpose of this analytical review was to estimate the direct and indirect economic costs of physical inactivity and obesity in Canada in 2001. The relative risks of diseases associated with physical inactivity and obesity were determined from a meta-analysis of existing prospective studies and applied to the health care costs of these diseases in Canada. Estimates were derived for both the direct health care expenditures and the indirect costs, which included the value of economic output lost because of illness, injury-related work disability, or premature death. The economic burden of physical inactivity was $5.3 billion ($1.6 billion in direct costs and $3.7 billion in indirect costs) while the cost associated with obesity was $4.3 billion ($1.6 billion of direct costs and $2.7 billion of indirect costs). The total economic costs of physical inactivity and obesity represented 2.6% and 2.2%, respectively, of the total health care costs in Canada. The results underscore the importance of public health efforts aimed at combating the current epidemics of physical inactivity and obesity in Canada. Key words: overweight, lifestyle, meta analysis, population attributable risk, cost-of-illness

Environmental factors affect colon carcinoma and rectal carcinoma in men and women differently

BACKGROUND AND AIMS

Colon cancer is thought to be more closely associated with environmental factors than rectal cancer, but evidence is currently insufficient. We examined whether there are differences in the degree of environmental effect on colon cancer and rectal cancer in Japan.

METHODS

We performed a birth cohort analysis for colon and rectal cancers using Japanese vital statistics from 1950 to 1998 and analyzed time trends by cancer site and gender.

RESULTS

The mean annual increase in age-adjusted mortality rate from colon cancer was greater than that from rectal cancer and was greater in men than in women. In men left colon cancer showed the greatest rate of increase whereas cancer of the right colon showed only a slight change. Although left colon cancer rapidly increased until the middle 1980s and thereafter showed no change, right colon cancer showed no change until the middle 1980s and thereafter rapidly increased in men. However, the rates of increase in left colon cancer were greater than those in right colon cancer until the middle 1980s, after which a reversal in trend was seen in women. Birth cohort analysis indicates that for all cohorts the mortality rates at the same age were higher in the recent cohorts than in the previous ones. This trend was more marked for colon cancer than for rectal cancer and was stronger among men than among women.

CONCLUSION

Colon cancer is more closely associated than rectal cancer with environmental factors, and this association is more pronounced in men than in women. Consequently cancers at these two sites should not be combined in studies of the role of lifestyle factors in causing these neoplasms. Furthermore, the causes of these diseases may differ in men and women.

Exercise and gastrointestinal function and disease: an evidence-based review of risks and benefits

BACKGROUND & AIMS

Exercise is beneficial to health because it reduces the risk of cardiovascular and endocrine diseases, improves bone and muscle conditioning, and lessens anxiety and depression. However, the impact of exercise on the gastrointestinal system has been conflicting. This systematic literature review evaluates the effect of the different modes and intensity levels of exercise on gastrointestinal function and disease using an evidence-based approach. Although more applicable to trained athletes and individuals who are highly active and, as such, at risk to experience the side-effects of exercise, an effort was made to state the level or degree of exercise or the lack of such evidence.

RESULTS

Light and moderate exercise is well tolerated and can benefit patients with inflammatory bowel disease and liver disease. Physical activity can also improve gastric emptying and lower the relative risk of colon cancer in most populations. Severe, exhaustive exercise, however, inhibits gastric emptying, interferes with gastrointestinal absorption, and causes many gastrointestinal symptoms, most notably gastrointestinal bleeding.

CONCLUSIONS

This knowledge will enable physicians to prescribe physical exercise in health and disease and to better manage patients with exercise-related gastrointestinal disorders. Our understanding of exercise and its gastrointestinal manifestations as well as risks and benefits warrants further investigation.

Physical activity and cancer prevention: etiologic evidence and biological mechanisms

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

The Swedish Twin Registry: a unique resource for clinical, epidemiological and genetic studies

The Swedish Twin Registry (STR), which today has developed into a unique resource, was first established in the late 1950s to study the importance of smoking and alcohol consumption on cancer and cardiovascular diseases whilst controlling for genetic propensity to disease. Since that time, the Registry has been expanded and updated on several occasions, and the focus has similarly broadened to most common complex diseases. In the following, we will summarize the content of the database, describe for the first time recent data collection efforts and review some of the principal findings that have come from the Registry.

Primary prevention of colorectal cancer: diet and drugs

Primary prevention of colonic adenomas and cancer through dietary interventions or chemoprevention has great appeal. This article discusses primary prevention goals and promising nutritional or chemopreventive strategies. There is substantial observational evidence that diets high in total calories and fat and or low in fruits and vegetables or total fiber as well as low levels of physical activity are related to the risk of colonic neoplasia. Similar observational data indicate that diets high in specific nutrients such as antioxidant vitamins or calcium may be protective. The article describes some of the newer chemopreventive agents and reviews the data linking diet and lifestyle to colorectal cancer risk, focusing on interventions that have also been studied in prospective clinical trials. Finally the evidence supporting the role of non-steroidal anti-inflammatory drugs for the chemoprevention of CRC is reviewed and the status of several other promising newer agents that are entering human trials is summarized.

Prevention and chemoprevention of colorectal neoplasms

Main purpose of the review is to analyse the impact of the current approaches for colorectal cancer prevention, including chemoprevention. Available evidence does not support the contention that a more appropriate diet can be of great help in the prevention of these neoplasms, either because the scientific evidence is poor and highly controversial, or because changes in diet are difficult to implement, at least in many Western countries. Similarly, a preventive approach based on the modification of lifestyle remains improbable, either in the short --or in the long period of time. Secondary prevention--i.e., the systematic removal of adenomatous polyps--can hardly be applied in the general population, with the exception of individuals at risk because members of families with Adenomatosis coli or Lynch syndrome, or affected by inflammatory bowel diseases. Finally, chemoprevention (i.e., the attempt to prevent tumour development through the administration of drugs or natural compounds that interfere with various phases of carcinogenesis) is still in its infancy Though attractive, this approach requires well-designed studies which should be carried out for years before being evaluated and interpreted; so far most of these investigations gave inconsistent or controversial results. In conclusion, both primary and secondary prevention of colorectal malignancies appear difficult to apply in the general population, and chemoprevention is still at the beginning of a (presumably] long story. The final impression is that notwithstanding the remarkable advancements made in the last two decades in colorectal cancer research, the practical application of these new concepts remains difficult.

Relationship of leisure-time physical activity and occupational activity to the prevalence of obesity

OBJECTIVE

To assess the interaction between leisure-time physical activity (LTPA) and occupational activity (OA) on the prevalence of obesity.

DESIGN

Secondary data analysis of a population based cross-sectional US national sample (NHANES III).

SUBJECTS

A total of 4889 disease-free, currently employed adults over age 20 y.

MEASUREMENTS

Subjects body mass index (BMI) was categorized as (1) obese (BMI> or =30 kg/m(2)), or (2) non-obese (BMI<30 kg/m(2)). LTPA was divided into four categories: (1) no LTPA; (2) irregular LTPA; (3) regular moderate intensity LTPA; and (4) regular vigorous intensity LTPA. OA was grouped as (1) high OA and (2) low OA. Age, gender, race-ethnicity, smoking status, urbanization classification, alcohol consumption and income were statistically controlled.

RESULTS

In all, 16.8% (s.e. 0.7) of the total subject population were obese (15.1% (s.e. 1.1) of men and 19.1% (s.e. 1.1) of women). Logistic regression revealed that compared to those who engage in no LTPA and have low levels of OA, the likelihood of being obese is 42% (95% CI 0.35, 0.96) lower for those who engage in no LTPA and have high OA, 48% (95% CI 0.32, 0.83) lower for those who have irregular LTPA and have high levels of OA, and about 50% lower for all those who have regular LTPA through moderate or vigorous activity levels regardless of OA level.

CONCLUSION

When considering disease free adults above 20 y of age employed in high and low activity occupations, a high level of occupational activity is associated with a decreased likelihood of being obese.

Insulin, insulin-like growth factors and colon cancer: a review of the evidence

Insulin and insulin-like growth factor (IGF) axes are major determinants of proliferation and apoptosis and thus may influence carcinogenesis. In various animal models, modulation of insulin and IGF-1 levels through various means, including direct infusion, energy excess or restriction, genetically induced obesity, dietary quality including fatty acid and sucrose content, inhibition of normal insulin secretion and pharmacologic inhibition of IGF-1, influences colonic carcinogenesis. Human evidence also associates high levels of insulin and IGF-1 with increased risk of colon cancer. Clinical conditions associated with high levels of insulin (noninsulin-dependent diabetes mellitus and hypertriglyceridemia) and IGF-1 (acromegaly) are related to increased risk of colon cancer, and increased circulating concentrations of insulin and IGF-1 are related to a higher risk of colonic neoplasia. Determinants and markers of hyperinsulinemia (physical inactivity, high body mass index, central adiposity) and high IGF-1 levels (tall stature) are also related to higher risk. Many studies indicate that dietary patterns that stimulate insulin resistance or secretion, including high consumption of sucrose, various sources of starch, a high glycemic index and high saturated fatty acid intake, are associated with a higher risk of colon cancer. Although additional environmental and genetic factors affect colon cancer, the incidence of this malignancy was invariably low before the technological advances that rendered sedentary lifestyles and obesity common, and increased availability of highly processed carbohydrates and saturated fatty acids. Efforts to counter these patterns are likely to have the most potential to reduce colon cancer incidence, as well as cardiovascular disease and diabetes mellitus.

Physical activity and cancer risk: dose-response and cancer, all sites and site-specific

PURPOSE

The association between physical activity and overall and site-specific cancer risk is elaborated in relation to whether any observed dose-response association between physical activity and cancer can be interpreted in terms of how much physical activity (type, intensity, duration, frequency) is needed to influence site- and gender-specific cancer risk.

METHODS

Observational studies were reviewed that have examined the independent effect of the volume of occupational physical activity (OPA) and/or leisure time physical activity (LPA) on overall and site-specific cancer risk.

RESULTS

The evidence of cohort and case-control studies suggests that both leisure time and occupational physical activity protect against overall cancer risk, with a graded dose-response association suggested in both sexes. Confounding effects such as diet, body weight, and parity are often included as a covariate in the analyses, with little influence on the observed associations. A crude graded inverse dose-response association was observed between physical activity and colon cancer in 48 studies including 40,674 colon/colorectal cancer cases for both sexes. A dose-response effect of physical activity on colon cancer risk was especially observed, when participation in activities of at least moderate activity (>4.5 MET) and demonstrated by activities expressed as MET-hours per week. An observed inverse association with a dose-response relationship between physical activity and breast cancer was also identified in the majority of the 41 studies including 108,031 breast cancer cases. The dose-response relationship was in particular observed in case-control studies and supported by observations in cohort studies when participation in activities of at least moderate activity (>4.5 MET) and demonstrated by activities expressed by MET-hours per week. This association between physical activity and breast cancer risk is possibly dependent on age at exposure, age at diagnosis, menopausal status and other effect modifiers, e.g., body mass index. Furthermore, data concerning carcinoma of other cancers (prostate, lung, endometrium, ovary, and testicular cancers) are required.

CONCLUSION

A protective effect of physical activity on site-specific cancer risk with a dose-response association between physical activity and colon and pre- and postmenopausal breast cancer supported by identified biological mechanisms has been observed. The optimal permutation of type, intensity, duration, and frequency of physical activity across the lifespan is unclear, but it is gender, age, and site specific and supports moderate activity (>4.5 MET) more than light activities (<4.5 MET). The complicated nature of the physical activity variable, combined with lack of knowledge regarding possible biological mechanisms operating between physical activity and cancer, warrants further studies including controlled clinical randomized trials.

Gastric and colorectal cancer mortality in an urban and industrialized area of Brazil

PURPOSE

To study the gastric and colorectal cancer mortalities and their relation to the urban-industrialization in Baixada Santista, located in the southeastern region of Brazil.

METHODS

Selected from the registries of the State System of Data Analysis Foundation (SEADE) were 1105 deaths due to gastric cancer (ICD 153 - 154) and 690 due to colorectal cancer (ICD 151) that occurred from 1980 to 1993 in males, above 10 years of age, residing in Baixada Santista. For each of these types of cancer, the standardized mortality rates, age-adjusted by world population in the 1960s, for 4 industrialized and 4 non-industrialized urban communities in that region were calculated. The ratios among those rates were calculated in order to compare the mortality in the periods 1980 - 93, 1980 - 1986, and 1987 - 1993.

RESULTS

Standardized mortality rates for colorectal cancer were significantly higher in industrialized area, with ratios of 1.6 [95% CI 1.22 - 2.29], 1.6 [95% CI 1.2 - 2.0], and 1.6 [95% CI 1.3 - 2.0] in the periods 1980 - 86, 1987 - 1993 and 1980 - 93, respectively. Gastric cancer did not show any statistical difference between the industrialized and non-industrialized areas, but there was a significant decrease in BS from the period 1980 - 1986 to 1987 - 1993.

CONCLUSIONS

The significant elevation of colorectal cancer mortality in the industrialized area could be related to exposure to numerous carcinogens such as aromatic hydrocarbon, organic-chloride, metals, and industrial-port dust present in the region. Alternatively, the non-significant difference in gastric cancer between industrialized and non-industrialized areas and significant decrease in the last few years could be predominately reflecting the advances in the quality of life in urban areas. These results require further case-control studies that could help with the analysis of the associations among cancer and environmental factors (occupational, urban-industrial, habit, and life condition) and genetic susceptibility.

Assessments of physical activity and cancer risk

The assessment of physical activity is one of the most important methodological issues in research into physical activity and cancer risk. A sedentary Western lifestyle has been observed to influence biological mechanisms promoting development of certain types of cancer. At present the totality of evidence supports a protective effect against cancers of the colon and probably the breast, while further data concerning carcinoma of other cancers are required. Thus, physical activity represents a powerful public health measure for reducing cancer risk. Studies of the association between physical activity and cancer risk have used a great variety of methods, but have most often included work and/or leisure time activity. Questionnaires are the method most often used and various components of physical activity such as type, frequency, intensity and lifetime physical activity have been recorded. However, the measurements used when assessing physical activity have been hampered by lack of accuracy as regards validity and reliability, missing information on the various components of physical activity and sparse information of lifetime exposure, and often no repeat assessments in cohort studies. Discrepancies between studies elaborating the association between physical activity and site-specific cancer risk may be explained through real differences or lack of information on the various components of physical activity (type, intensity, duration) and incomplete information about the cancer type studied (localization, histological type). The complicated nature of the variable physical activity, combined with incomplete understanding of the pathogenesis of most cancer and lack of knowledge regarding possible biological mechanisms operating between physical activity and cancer, warrants further studies. In these studies methodological improvements in measuring physical activity, combined with inclusion of physiological markers (heart rate, energy balance, hormonal levels, etc.) reflecting the variety of physical activities performed are of particular interest. Assessing biomarkers and intermediate steps for site-specific cancer risk may give us further insight into the relation between physical activity and cancer that will be of enormous interest for public health recommendations.

Combined risk assessment of physical activity and dietary habits on the development of colorectal cancer. A hospital-based case-control study in Poland

The purpose of the study was to assess the importance of physical activity performed both in occupational settings and in leisure time on the risk of colorectal cancer, considering the possible confounding effects of dietary habits. The hospital-based case-control study was carried out in Poland. In total, 180 incident cases of colorectal cancer were recruited. An equal number of controls, individually matched by gender and age, were chosen from patients with no history of cancer. A food frequency questionnaire combined with quantity of foods eaten was used to assess the usual dietary pattern for 148 food items. The average physical load of the interviewed patients before the occurrence of disease was ascertained by self-assessment. The degree to which patients' recreational time was sedentary was measured by the number of hours spent watching TV. The adjusted risk of colorectal cancer was reduced by half in those active in leisure time (OR 0.45, 95% CI 0.24-0.84). The effect of occupational physical activity was of about the same order of magnitude in terms of risk reduction (OR 0.61, 95% CI 0.29-1.29) and both activities combined acted as independent protective factors. The protective effect of healthy nutrition appeared to be independent from that attributed to physical effort.

Moderate intensity exercise training improves cardiorespiratory fitness in women

Among women, there is an increased prevalence of sedentary lifestyle and less participation in physical activity at levels recommended by the Surgeon General. As a result, women have been identified as a target group in public health initiatives to increase physical activity. The health-related benefits of habitual, moderate intensity physical activity are well documented in the epidemiological literature, but less is known about the effect of such physical activity on cardiorespiratory fitness. Our hypothesis was that moderate and vigorous exercise training regimens of similar estimated energy expenditure would result in similar changes in cardiorespiratory fitness. Eighteen sedentary premenopausal women with the following baseline characteristics [x +/- SE]: maximal oxygen consumption (Vo2max) = 29.5+/-1.5 ml x kg(-1) x min(-1); age = 33+/-1 years; height = 162.6+/-0.9 cm; mass = 62.7+/-2.3 kg, were randomly assigned to either vigorous (HI, 80% Vo2max, n = 10) or moderate intensity (MOD, 40% Vo2max, n = 8) cycle ergometer training groups. Exercise training was conducted 3-4 (3.37+/-0.05) days/week for 12 weeks in a supervised and progressive manner, with estimated exercise energy expenditure equated across both training groups. Vo2max and time to exhaustion increased significantly in both groups (p<0.05), with no difference between groups. Both groups had lower (p<0.05) posttraining submaximal heart rates (HR), respiratory exchange ratios (RER), and ratings of perceived exertion (RPE) during graded exercise testing, with no significant differences between the groups in posttraining values. Women participating in moderate intensity exercise training as recommended in basic public health guidelines demonstrate an increase in cardiorespiratory fitness similar to that elicited by vigorous training.

The Working Healthy Project: a worksite health-promotion trial targeting physical activity, diet, and smoking

Worksites are a key channel for delivery of interventions designed to reduce chronic disease among adult populations. Although some evaluations of worksite physical-activity interventions have been conducted, to date very few randomized trials of worksite health promotion have included the goal of increasing physical-activity levels as part of a comprehensive multiple risk factor approach to worksite health promotion. This article presents the results regarding behavior change found among the cohort of 2055 individuals who completed three health-behavior assessments as part of their worksites' participation in The Working Healthy Project (WHP), a multiple risk factor intervention implemented in 26 manufacturing worksites. In this study, a randomized matched-pair design was used. Fifty-one percent (n = 2,761) of the employees who completed the baseline assessment also completed the interim survey. Eighty-three percent of those who completed the interim assessment also completed the final survey. The WHP intervention targeted smoking, nutrition, and physical activity. At baseline, 38% of the sample reported engaging in regular exercise, and subjects reported consuming an average of 2.7 servings of fruits and vegetables per day, 7.9 grams of fiber per 1000 kilocalories, and 35.4% calories from fat per day; 28% of the sample were smokers. By the time of both the interim (intervention midpoint) and final (end of intervention) assessments, participants in the intervention condition had significantly increased their exercise behavior, compared with the control condition. There was also increased consumption of fruits and vegetables and fiber in the intervention condition by the time of the final assessment, compared with the control condition. No differences by condition were found with regard to percentage of calories from fat consumed or smoking cessation. These results suggest that among a cohort of participants in a worksite health promotion study, there were significant health behavior changes across two risk factors over time. These data suggest that further investigation of multiple risk factor worksite health promotion is warranted, particularly with a focus on ways to increase participation in these programs and to diffuse intervention effects throughout the entire workforce.

Occupational physical activity and non-Hodgkin's lymphoma

PURPOSE

The purpose of this study was to evaluate the role of physical activity in the development of non-Hodgkin's lymphoma (NHL).

METHODS

Incident NHL cases and population-based controls were identified from three case-control studies conducted in four midwestern states: Iowa, Kansas, Minnesota, and Nebraska. A total of 1177 cases (993 men, 184 women) and 3625 controls (2918 men, 707 women) were interviewed. Usual occupation (all states) and lifetime occupational histories (Iowa and Minnesota only), obtained from interviews, were classified for energy expenditure (EE) and sitting time. Odds ratios (OR) and 95% confidence intervals were calculated comparing moderate and high activity levels with sedentary levels.

RESULTS

There was no evidence of an association between NHL and occupational physical activity measured either by EE or sitting time. Among men, the OR associated with usual occupation moderate and high EE were 1.1 and 1.0, respectively. For sitting time, the OR were also 1.1 and 1.0 for moderate and high activity, respectively. Among women, slight nonsignificant elevations in risk of NHL were observed among the high energy level and high activity sitting categories. The trends were not significant. There was no evidence of confounding or effect modification by vital status, hair dye use, or solvent exposure. Among subjects with lifetime occupational histories, there were no significant increases or trends for cumulative or average EE or sitting time. There was no association between occupational physical activity and NHL.

CONCLUSION

Research on nonoccupational physical activity, which in the U.S. is likely the more important component of daily activity than occupational activity, may still be warranted given the laboratory evidence linking physical activity and immune function, an important factor in the etiology of NHL.