April 09, 2019
3 min read

Sedentary TV viewing linked to increased risk for young-onset colorectal cancer

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

Photo of Long Nguyen
Long H. Nguyen

Sedentary TV viewing for prolonged periods of time appeared associated with an increased risk for young-onset colorectal cancer, especially rectal cancer, according to results of a prospective study published in JNCI Cancer Spectrum.

Researchers observed this association independent of outside factors such as exercise and obesity and frequently among those 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, 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.”

Rates of young-onset colorectal cancer, diagnosed before age 50 years, are increasing in the United States, parts of Europe and in Asia despite sharp declines among men and women age 50 years and older, which researchers attributed to cancer screening initiatives.

Rates of rectal cancer are rising faster than rates of colon cancer among younger people. By 2030, rectal cancer cases are projected to increase 124% among people ages 20 to 34 years and 46% among people ages 35 to 49 years, according to study background.

Cao and colleagues analyzed sedentary behaviors, primarily TV viewing, and risk for colorectal cancer among 89,278 women ages 25 to 42 years in the prospective Nurses Health Study II.

Long H. Nguyen, MD, gastroenterology fellow at Massachusetts General Hospital and lead study author, said the Nurses Health Study II was used because the patients, although all female, were in their mid-20s to early-40s at recruitment. It offered a unique opportunity to look at how sedentary behavior is related to the risk for colorectal cancer before age 50, which is when the average-risk individual begins routine screening.

“Validation of these findings in other groups, including men who tend to have higher rates of colorectal cancer than females, would be important and a logical next step,” Nguyen told HemOnc Today. “However, it is interesting to note that in prior work by our group — focused on sedentary behaviors in older men and women — the colorectal cancer risk estimates in women were significantly higher than in men. [Risk] in younger men may appear to more closely mirror their female counterparts. Regardless, more work will need to be done in this area.”


Colorectal cancer diagnosed before age 50 years served as the primary endpoint.

Median follow-up was 13.9 years.

Researchers documented 118 cases of young-onset colorectal cancer over 1,262,540 person-years. Median age of diagnosis was 45 years (interquartile range, 41-47 years).

Results showed a statistically significant association between sedentary TV watching time and increased risk for young-onset colorectal cancer.

Women who watched 7.1 hours to 14 hours of TV every week had a multivariable RR of 1.12 (95% CI, 0.72-1.75) compared with women who watched 7 hours or less per week. Women who watched more than 14 hours of TV per week had an even greater risk (RR = 1.69; 95% CI, 1.07-2.67).

The association between TV viewing and young-onset colorectal cancer risk appeared particularly strong for rectal cancer (RR for > 14 hours vs. < 7 hours per week = 2.44; 95% CI, 1.03-5.78). Researchers could not find any clear associations between risk and other sedentary behaviors at home, such as having meals or spending time at a desk.

Nguyen and colleagues wrote sedentary TV viewing could lead to unhealthy snacking and a decrease in energy expenditure, leading to the higher risk for colorectal cancer.

Researchers did not assess time using computers, tablets or smartphones, which they cited as a limitation to this study. However, because the study period was between 1991 and 2011, those habits, particularly smartphone use, were not as common.

“The use of such devices occurs in more mobile, less stationary settings distinct from the somewhat sustained positions and postures that typify homebound TV time, and would warrant additional study independent of the results shown here,” Nguyen said. “The prevalence of streaming services and so-called ‘binge’ TV watching may be increasing, which would contribute to prolonged, unbroken time spent sitting. As media consumption habits continue to change, we will need to continually assess how such behavior could be contributing to our disease risk.”– by John DeRosier

For more information:

Long H. Nguyen, MD, can be reached at Massachusetts General Hospital, 55 Fruit St., Boston, MA 02114; email: lnguyen24@mgh.harvard.edu.

Disclosures: The Crohn’s and Colitis Foundation, Massachusetts General Hospital NIH and Raymond P. Lavietes Foundation supported this study. The authors report no relevant financial disclosures.