A new study in JNCI Cancer Spectrum has identified a connection between prolonged time spent sitting while watching TV and increased risk of colorectal cancer for younger Americans.

Young-onset colorectal cancer, diagnosed under age 50, is increasing in the US and globally, sharply contrasting with the dramatic decreases among older people, largely as a result of cancer screening initiatives. Young-onset colorectal cancer has potentially different molecular characteristics compared to those of late-onset, and is typically more aggressive and found at a more advanced stage than those in older patients, resulting in greater years of life lost. Despite these trends, researchers have identified few risk factors specific to young-onset colorectal cancer.

Researchers here studied sedentary TV reviewing time, as well as other sedentary behaviors, in 89,278 American women in the Nurses' Health Study II. Of the 118 cases of young-onset colorectal cancer diagnosed over two decades of follow up, more than one hour of daily TV viewing time was associated with a 12% increase in risk compared to those who watched less. The results were even more striking for those watching more than two hours/day with a nearly 70% increase in risk. This association was independent of BMI and exercise and was consistently observed among women without a family history of colorectal cancer. The association was also more pronounced for rectal cancer compared to colon cancer.

These findings are among the first to link specific sedentary behavioral patterns with risk of young-onset colorectal cancer. "This study may help identify those at high risk and who might benefit more from early screening," said Yin Cao, Assistant Professor of Surgery at Washington University School of Medicine, and the study's co-senior author. "The fact that these results were independent of BMI and physical activity suggests that being sedentary may be an altogether distinct risk factor for young-onset colorectal cancer."

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The paper, "Sedentary Behaviors, TV Viewing Time, and Risk of Young-Onset Colorectal Cancer," is available (at midnight EST on February 5) at: https:/ / doi. org/ 10. 1093/ jncics/ pky073

Direct correspondence to:

To contact corresponding author Yin Cao, M.P.H., Sc.D., email Jim Goodwin at jgoodwin@wustl.edu.

To request a copy of the study, please contact:

Daniel Luzer

daniel.luzer@oup.com

This work was supported by the National Institutes of Health (UM1CA176726, R01CA137178, R01CA205406, R35CA197735, K24DK098311 to ATC, T32CA009001 to LHN); the Crohn's and Colitis Foundation (Senior Investigator Award to ATC, Research Fellowship Award to LHN); National Research Foundation of Korea (NRF-2018R1C1B6008822 & NRF-2018R1A4A1022589 to NK); Massachusetts General Hospital (Stuart and Suzanne Steel Research Scholars Award to ATC); the Raymond P. Lavietes Foundation (Young Investigator Award to YC).