The findings are further evidence of the impact of an active lifestyle on physical health.
A study from JNCI Cancer Spectrum has found that sedentary behaviors, such as watching TV, lead to a significant increased risk of young-onset colorectal cancer in young Americans.
Rates of young-onset colorectal cancer (CRC) diagnosed before age 50 are increasing globally. This is in contrast to the dramatic decrease of CRC, typically diagnosed in those around age 65, as a result of cancer screening initiatives. According to the study, young-onset CRC has potentially different molecular characteristics compared to late onset. It is typically diagnosed at a more advanced stage than conventional CRC and includes more aggressive tumors, different clinicopathological characteristics, and greater years of life lost.
The researchers evaluated sedentary behaviors, such as time watching TV, in over 89,278 women, ages 25 to 42 years in the Nurses’ Health Study II. Of the 118 cases of young-onset colorectal cancer diagnosed over 2 decades of follow up, more than 1 hour of daily TV viewing time was associated with a 12% increase in risk compared to those who watched less, according to the study. For those watching 2 hours per day, there was a near 70% increase in risk of young-onset CRC, particularly of the rectum. This association of risk was independent of obesity and exercise and was consistently observed among women without a family history of colorectal cancer.
"This study may help identify those at high risk and who might benefit more from early screening," Yin Cao, MPH, ScD, Assistant Professor of Surgery at Washington University School of Medicine, and the study's co-senior author, said in a press release. "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."
These findings are among the first to link specific sedentary behavioral patterns with the risk of young-onset colorectal cancer.