title: Association of Physical Activity by Type and Intensity With Digestive System Cancer Risk.
abstract: OBJECTIVE
  Accumulating evidence indicates that common carcinogenic pathways may underlie digestive system cancers. Physical activity may influence these pathways. Yet, to our knowledge, no previous study has evaluated the role of physical activity in overall digestive system cancer risk.
  
  
  OBJECTIVE
  To examine the association between physical activity and digestive system cancer risk, accounting for amount, type (aerobic vs resistance), and intensity of physical activity.
  
  
  METHODS
  A prospective cohort study followed 43 479 men from the Health Professionals Follow-up Study from 1986 to 2012. At enrollment, the eligible participants were 40 years or older, were free of cancer, and reported physical activity. Follow-up rates exceeded 90% in each 2-year cycle.
  
  
  METHODS
  The amount of total physical activity expressed in metabolic equivalent of task (MET)-hours/week.
  
  
  METHODS
  Incident cancer of the digestive system encompassing the digestive tract (mouth, throat, esophagus, stomach, small intestine, and colorectum) and digestive accessory organs (pancreas, gallbladder, and liver).
  
  
  RESULTS
  Over 686 924 person-years, we documented 1370 incident digestive system cancers. Higher levels of physical activity were associated with lower digestive system cancer risk (hazard ratio [HR], 0.74 for ≥63.0 vs ≤8.9 MET-hours/week; 95% CI, 0.59-0.93; P value for trend = .003). The inverse association was more evident with digestive tract cancers (HR, 0.66 for ≥63.0 vs ≤8.9 MET-hours/week; 95% CI, 0.51-0.87) than with digestive accessary organ cancers. Aerobic exercise was particularly beneficial against digestive system cancers, with the optimal benefit observed at approximately 30 MET-hours/week (HR, 0.68; 95% CI, 0.56-0.83; P value for nonlinearity = .02). Moreover, as long as the same level of MET-hour score was achieved from aerobic exercise, the magnitude of risk reduction was similar regardless of intensity of aerobic exercise.
  
  
  CONCLUSIONS
  Physical activity, as indicated by MET-hours/week, was inversely associated with the risk of digestive system cancers, particularly digestive tract cancers, in men. The optimal benefit was observed through aerobic exercise of any intensity at the equivalent of energy expenditure of approximately 10 hours/week of walking at average pace. Future studies are warranted to confirm our findings and to translate them into clinical and public health recommendation.
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
authors.forename: NaNa
authors.initials: N
authors.lastname: Keum
authors.affiliation: Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Ying
authors.initials: Y
authors.lastname: Bao
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts3Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Smith-Warner
authors.affiliation: Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, Massachusetts5Department of Medicine, Harvard Medical School, Boston, Massachusetts.
authors.forename: John
authors.initials: J
authors.lastname: Orav
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
authors.forename: Kana
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Medicine, Harvard Medical School, Boston, Massachusetts6Department of Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fuchs
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts2Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts3Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts5Department of Medicine, Harvard Medical School, Boston, Massachusetts.
authors.forename: Edward L
authors.initials: EL
authors.lastname: Giovannucci
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology; D003920:Diabetes Mellitus / Q000453:epidemiology; D004067:Digestive System Neoplasms / Q000453:epidemiology*; D004938:Esophageal Neoplasms / Q000453:epidemiology; D015444:Exercise; D005500:Follow-Up Studies; D005706:Gallbladder Neoplasms / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007414:Intestinal Neoplasms / Q000453:epidemiology; D008113:Liver Neoplasms / Q000453:epidemiology; D008297:Male; D055686:Metabolic Equivalent; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000453:epidemiology; D015999:Multivariate Analysis; D009765:Obesity / Q000453:epidemiology; D010190:Pancreatic Neoplasms / Q000453:epidemiology; D010610:Pharyngeal Neoplasms / Q000453:epidemiology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D055070:Resistance Training / Q000706:statistics & numerical data*; D013274:Stomach Neoplasms / Q000453:epidemiology; D014481:United States / Q000453:epidemiology