• Yin Cao, Jeffrey A Meyerhardt, Andrew T Chan, Kana Wu, Charles S Fuchs, and Edward L Giovannucci.
• Department of Nutrition, Harvard T. H. Chan School of Public Health, 665 Huntington Avenue, Boston, MA, 02115, USA. yic576@mail.harvard.edu.
• Cancer Causes Control. 2015 Oct 1; 26 (10): 1467-76.

PurposeTo assess the association between pre- and postdiagnostic time spent sitting watching TV as well as other sedentary behaviors (other sitting at home and at work/driving) and mortality from colorectal cancer or other causes, and overall mortality.MethodsWe followed stage I-III colorectal cancer patients from the Health Professionals Follow-up Study (1986-2010). Cox models were used to calculate hazard ratios (HRs) and 95 % confidence intervals (CIs).ResultsA total of 926 and 714 patients were included in the analysis of pre- and postdiagnostic TV watching, respectively, and 471 and 325 died during follow-up. Prolonged prediagnostic TV viewing was associated with increased risk of colorectal cancer-specific mortality independent of leisure-time physical activity. The HRs (95 % CIs) for 0-6, 7-13, 14-20, and ≥21 h/week were 1.00 (referent), 0.84 (0.56-1.25), 1.15 (0.75-1.78), and 2.13 (1.31-3.45) (p trend = 0.01). The association was observed primarily among overweight and obese individuals. Prediagnostic TV watching was also associated with overall mortality within 5 years of diagnosis, largely due to the association with colorectal cancer mortality. Other prediagnostic sitting at home or at work/driving was not associated with mortality. Postdiagnostic TV viewing was associated with a nonsignificantly increased risk of colorectal cancer-specific mortality (HR for ≥21 vs 0-6 h/week = 1.45; 95 % CI 0.73-2.87) adjusting for TV viewing before diagnosis.ConclusionProlonged prediagnostic TV watching is associated with higher colorectal cancer-specific mortality independent of leisure-time physical activity among colorectal cancer patients.

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