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Original Investigation
September 2016

Association of Physical Activity by Type and Intensity With Digestive System Cancer Risk

Author Affiliations
  • 1Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 2Channing Division of Network Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
  • 3Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 4Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 5Department of Medicine, Harvard Medical School, Boston, Massachusetts
  • 6Department of Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
JAMA Oncol. 2016;2(9):1146-1153. doi:10.1001/jamaoncol.2016.0740

Importance  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.

Design, Setting, and Participants  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.

Exposures  The amount of total physical activity expressed in metabolic equivalent of task (MET)-hours/week.

Main Outcomes and Measures  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 and Relevance  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.