Physical activity and risk of colorectal cancer in Japanese men and women: the Japan Public Health Center-based prospective Study
ABSTRACT To prospectively examine the association between physical activity and the risk of developing colorectal cancer in a large population-based cohort study of Japanese men and women, and to investigate whether the effects of physical activity on colorectal cancer risk differ by sex and subsite.
We analyzed data from a population-based cohort of 65,022 subjects. A total of 486 incident colorectal cancers (154 proximal colon, 166 distal colon and 149 rectal cancers) was identified during 6 years of follow-up.
We observed a significant inverse association between physical activity and the risk of developing colorectal cancer, particularly colon cancer, among men. Relative to men in the lowest level of metabolic equivalent (MET) hours per day, those in the highest level had a RR of 0.69 (95% CI = 0.49-0.97). A significant decrease in risk of colorectal cancer was associated with increasing MET hours per day among men. This inverse association was essentially limited to colon cancer. A significant decrease in risk with increasing MET-hour score was observed predominantly for proximal colon cancer among men. In contrast, no significant decrease was seen among women.
These findings suggest that physical activity may prevent colon cancer among Japanese men.
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ABSTRACT: Several studies report varying incidence rates of cancer in subsites of the colorectum, as an increasing proportion appears to develop in the proximal colon. Varying incidence trends together with biological differences between the colorectal segments raise questions of whether lifestyle factors impact on the risk of cancer differently at colorectal subsites. We provide an updated overview of the risk of cancer at different colorectal subsites (proximal colon, distal colon, and rectum) according to BMI and physical activity to shed light on this issue. Cohort studies of colorectal cancer, published in English throughout 2010, were identified using PubMed. The risk estimates from 30 eligible studies were summarized for BMI and physical activity. A positive relationship was found between BMI and cancer for all colorectal subsites, but most pronounced for the distal colon [relative risk (RR) 1.59, 95% confidence interval (CI) 1.34-1.89]. For the proximal colon and rectum, the risk estimates were 1.24 (95% CI 1.08-1.42) and 1.23 (95% CI 1.02-1.48), respectively. Physical activity was related inversely to the risk of cancer at the proximal (RR 0.76, 95% CI 0.70-0.83) and distal colon (RR 0.77, 95% CI 0.71-0.83). Such a relationship could not be established for the rectum (RR 0.98, 95% CI 0.88-1.08). In conclusion, the results suggest minor differences in the associations of BMI and the risk of cancer between the colorectal subsites. For physical activity, the association does not seem to differ between the colonic subsites, but a difference was observed between the colon and the rectum, perhaps indicating that different mechanisms are operating in the development of colon and rectal cancer.European journal of cancer prevention: the official journal of the European Cancer Prevention Organisation (ECP) 04/2013; 22(6). DOI:10.1097/CEJ.0b013e328360f434 · 2.76 Impact Factor
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ABSTRACT: This review evaluated the strength of the evidence for a causal relationship between physical activity (PA) and colorectal cancer (CRC). A systematic review of databases through February 2008 was conducted to identify studies that assessed the association between total or recreational PA and incidence or mortality of CRC (including CRC, rectal cancer, colon cancer, and proximal or distal colon cancer). Studies were evaluated for significant associations between PA and risk of CRC endpoints and for evidence of dose-response relationships in the highest quality studies. Twenty cohort studies were evaluated; 11 were high-quality. Fifty percent of all studies and 64% of highest quality studies reported at least one significant association between PA and risk of a CRC endpoint (P<0.05). However, only 28% of all analyses (31% of analyses of highest quality studies) were significant (P<0.05). Only 40% of analyses of highest quality studies resulted in a significant P for trend (P<0.05); however, a non-significant inverse linear association between PA and colon cancer risk was apparent. Heterogeneity in the evidence from all studies and from the highest quality studies was evident. Evidence from cohort studies is not sufficient to claim a convincing relationship exists between PA and CRC risk.Scandinavian Journal of Medicine and Science in Sports 09/2009; 19(6):764-81. DOI:10.1111/j.1600-0838.2009.00992.x · 3.17 Impact Factor
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ABSTRACT: Background: Calcium and vitamin D have a potential protective effect against colorectal cancer. Objective: We investigated the association of dietary intake of calcium and vitamin D with the risk of colorectal cancer in a large prospective cohort study of middle-aged Japanese men and women. Design:A total of 74 639 subjects (35 194 men and 39 445 women) who participated in the Japan Public Health Center-based Prospective Studywerefollowedfrom1995-1999totheendof2004,duringwhich time761casesofcolorectalcancer(464men,297women)werenewly identified. Dietary intake of nutrients was calculated with the use of a 138-item self-administered food-frequency questionnaire. Results: After adjusting for potential confounding factors, the multi- variate hazard ratio in the highest quintile of dietary calcium intake compared with the lowest was 0.71 (95% CI: 0.52, 0.98) among men. The association appeared to decrease considerably among subjects in thesecondquintilewithoutaclearfurtherdose-responserelation(Pfor trend: 0.09). No association was seen among women. No statistically significant association with dietary vitamin D intake was seen in either menorwomen,althoughmeninthehighestdietaryintakegroupofboth nutrients had a lower risk than did men in the lowest group. Conclusions:ThesefindingsindicateapotentialdecreaseintheriskThe Lancet 05/1985; 1(8434):925. DOI:10.1016/S0140-6736(85)91694-0 · 45.22 Impact Factor