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
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 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 behavioural 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.”

Source: https://www.eurekalert.org/pub_releases/2019-02/oupu-nss020419.php

Reference: Nguyen
LH, et al.  Sedentary Behaviors, TV Viewing Time, and Risk of Young-Onset
Colorectal Cancer. JNCI Cancer Spectrum,
Volume 2, Issue 4, 1 November 2018. Published 25 January 2019.