Consistent Adherence to Physical Activity Guidelines and Digestive System Cancer Risk and Mortality

Importance: Growing evidence suggests that physical activity protects against digestive system cancers (DSCs). However, it remains largely unknown whether consistently reaching the physical activity guidelines (≥7.5 metabolic equivalent task [MET]-hours/week) is associated with lower DSC risk or whether a much higher level is needed. Objective: To examine the association between physical activity and DSC risk and mortality with a focus on the optimal amount and long-term consistency in performing the recommended level over a long period of time. Design, Setting, and Participants: This population-based cohort study includes data from 3 large US prospective cohorts: Health Professionals Follow-Up Study, 1988-2020; Nurses' Health Study, 1988-2021; and Nurses' Health Study II, 1991-2021. Data analysis was performed between October 2024 and May 2025. Participants were men and women free from cancer and cardiovascular disease at baseline. Exposures: Total levels of leisure-time physical activity were assessed with biennial validated questionnaires and expressed in MET-hours per week. Consistency was calculated as the percentage of follow-up years meeting the recommended level (≥7.5 MET-hours/week). Main Outcomes and Measures: DSCs included cancers of digestive tract (mouth, throat, esophagus, stomach, small intestine, colon, and rectum) and digestive accessory organs (pancreas, gallbladder, and liver). Results: During up to 32 years of follow-up of 231 067 men and women (median age, 43 [IQR, 36-55] years), a total of 6538 incident DSCs and 3791 DSC deaths were documented. Higher physical activity levels were associated with lower DSC risk (≥45 vs <3 MET-hours/week; hazard ratio [HR], 0.83; 95% CI, 0.74-0.93; P < .001 for trend) and mortality (HR, 0.72; 95% CI, 0.62-0.83; P < .001 for trend). The inverse associations were evident for both digestive tract and accessory organ cancers: the HRs comparing greater than or equal to 45 vs 3 MET-hours/week were 0.85 (95% CI, 0.75-0.97) for digestive tract cancer risk and 0.73 (95% CI, 0.58-0.92) for digestive accessory organ cancer risk. The traditional dose-response analysis suggested the lowest DSC risk was achieved at approximately 50 MET-hours/week. However, when long-term consistency was considered, compared with those with minimal activity, consistently reaching the guideline at moderate levels (median, 16.9 [IQR, 13.6-20.5] MET-hours/week) over 3 decades was associated with substantial reductions in DSC risk (HR, 0.83; 95% CI, 0.75-0.90), whereas that performing much higher amounts (median, 38.5 [IQR, 28.5-53.8] MET-hours/week) was not associated with further benefit (HR, 0.87; 95% CI, 0.81-0.93). Conclusions and Relevance: In this study, traditional dose-response analysis suggested that approximately 50 MET-hours/week was associated with optimal DSC risk reduction. After incorporating long-term consistency, maintenance of a moderate level approximately 17 MET-hours/week over 3 decades was associated with achieving optimal benefit in reducing DSC risk.