Colorectal cancer: TV viewing tied to risk of early onset
Recent research has linked prolonged sitting while viewing TV to a raised risk of developing colorectal cancer before the age of 50 years.
This effect, which appeared to be strongest for cancer that starts in the rectum, was independent of exercise and body mass index (BMI).
When they diagnose colorectal cancer in people younger than 50 years, doctors generally refer to it as young-onset colorectal cancer.
The recent study, which now features in the journal JNCI Cancer Spectrum, is one of the first to link a particular sedentary behavior to a higher risk of young-onset colorectal cancer.
While others have already suggested that prolonged sitting while viewing TV could be a risk factor for colorectal cancer, they have not looked specifically at young-onset colorectal cancer.
The researchers behind the new study note that young-onset colorectal cancer is usually more aggressive than colorectal cancer that strikes later in life and is likely to have some distinct biological features.
Also, by the time diagnosis takes place, the cancer is usually more advanced, resulting in poorer rates of survival.
Senior study author Dr. Yin Cao, who is an assistant professor in the Department of Surgery at Washington University School of Medicine in St. Louis, MO, suggests that the new finding "may help identify those at high risk and who might benefit more from early screening."
Cancer of the colon and the rectum
Colorectal cancer is cancer that starts in the colon or the rectum, which together form the final section of the gut at the opposite end to the mouth, food pipe, and stomach.
With the help of bacteria, the colon breaks down undigested food and extracts water and salts from it.
The remains of that final stage of digestion then move into the rectum, which holds the waste pending evacuation through the anus in the form of stools.
In the majority of cases, colorectal cancer arises from small growths, or polyps, that form in the lining of that part of the gut.
It can take many years for polyps to turn into tumors, and not all polyps become cancerous.
The extent to which the tumor spreads, first into the wall of the gut and then beyond, determines the severity and stage of the cancer.
Globally, colorectal cancer is the third most common cancer, with an estimated 1.4 million new cases every year, according to 2012 statistics from the World Cancer Research Fund.
In the United States, surveillance by the National Cancer Institute suggests that colorectal cancer is the fourth most common cancer and that in 2015, approximately 1,332,085 people were living with the disease.
The study authors remark that although the overall incidence of colorectal cancer is falling in the U.S. and many other countries, this is not the case for young-onset colorectal cancer.
Although still relatively rare, rates of colorectal cancer among those aged 20–49 years "have increased dramatically," they note.
