title: Physical activity and colorectal cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population.
abstract: OBJECTIVE
  Higher levels of physical activity have been consistently associated with a decreased risk of colon cancer, but not rectal cancer, in Western populations. The present study systematically evaluated epidemiologic evidence on the association between physical activity and colorectal cancer risk among the Japanese population.
  
  
  METHODS
  Original data were obtained from MEDLINE searched using PubMed or from searches of the Ichushi database, complemented by manual searches. The associations were evaluated based on the strength of evidence, the magnitude of association and biologic plausibility.
  
  
  RESULTS
  Two cohort studies and six case-control studies were identified. A weak to strong protective association between physical activity and colon cancer risk was observed in both cohort studies, showing a graded relationship, and among the majority of case-control studies, with some showing a dose-response relationship. The association observed in cohort studies was more consistent and stronger in men than in women and for proximal colon cancer than for distal colon cancer. A protective association with rectal cancer was found only in case-control studies, but the evidence was less consistent and weaker than that observed for colon cancer.
  
  
  CONCLUSIONS
  Physical activity probably decreases the risk of colorectal cancer among the Japanese population. More specifically, the evidence for the colon is probable, whereas that for the rectum is insufficient.
authors: Department of Epidemiology and Prevention, International Clinical Research Center, National Center for Global Health and Medicine, Tokyo 162-8655, Japan. mizoue@ri.ncgm.go.jp
authors: Ngoc Minh
authors: NM
authors: Pham
authors: Tetsuya
authors: T
authors: Mizoue
authors: Keitaro
authors: K
authors: Tanaka
authors: Ichiro
authors: I
authors: Tsuji
authors: Akiko
authors: A
authors: Tamakoshi
authors: Keitaro
authors: K
authors: Matsuo
authors: Hidemi
authors: H
authors: Ito
authors: Kenji
authors: K
authors: Wakai
authors: Chisato
authors: C
authors: Nagata
authors: Shizuka
authors: S
authors: Sasazuki
authors: Manami
authors: M
authors: Inoue
authors: Shoichiro
authors: S
authors: Tsugane
mesh_terms: D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D015444:Exercise; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D011322:Primary Prevention; D040242:Risk Reduction Behavior