Sitting down to binge watch more than four hours of TV over a day could increase the risk of bowel cancer in men compared to those watching less than just an hour of TV, according to a paper published in the British Journal of Cancer.
In one of the largest studies to date investigating the link between sedentary behaviour and bowel cancer risk, researchers analysed data from more than half a million men and women and found that men who spent less time in front of the TV were also less likely to develop bowel cancer later in life.*
After six years of follow-up 2,391 people from the UK Biobank study went on to develop bowel cancer. When researchers from the International Agency for Research on Cancer (IARC), Imperial College London and the University of Oxford analysed the data they made the link between sedentary behaviour and bowel cancer.
They also found that an increase in physical activity was associated with lower colon cancer risk in men.** But, intriguingly, they found no link between computer screen time and bowel cancer risk.
Dr Neil Murphy, lead researcher based at IARC in France, said: “Previous research suggests that watching TV may be associated with other behaviours, such as smoking, drinking and snacking more, and we know that these things can increase the risk of bowel cancer.
“Being sedentary is also associated with weight gain and greater body fat. Excess body fat may influence the blood levels of hormones and other chemicals which affect the way our cells grow, and can increase bowel cancer risk.”
Bowel cancer is the third most commonly diagnosed cancer in UK men. In the UK there were around 41,800 newly diagnosed cases of bowel cancer in men and women in 2015.
Professor Linda Bauld, Cancer Research UK’s prevention expert, said: “This study poses interesting questions such as why screen time from computers didn’t increase the risk of bowel cancer but watching TV did. There is evidence that greater exposure to TV junk food adverts increases the likelihood of eating more, which will also increase your chances of becoming overweight.
“It’s interesting that only men who watched a lot of TV had an increased risk of bowel cancer, but not women. The study didn’t look at this directly, but it could be because men might smoke, drink and eat more unhealthily than women while watching TV.
“We’ll need further research to answer the questions this study raises. What we do know is that keeping a healthy weight, cutting back on alcohol, being physically active and eating a diet rich in fruit and vegetables are known to cut your risk of bowel cancer.”
Physical activity, sedentary behaviour and colorectal cancer risk in the UK Biobank. Morris JS, Bradbury KE, Cross AJ, Gunter MJ, and Murphy N. British Journal of Cancer (2018) doi: 10.1038/bjc.2017.496.
*Compared to those who watched one hour or less of TV per day, watching more than 4 hours a day was associated with a 35% greater risk of developing bowel cancer in men.
**Compared to the low physical activity group, a 23% reduced risk of developing colon cancer was observed for the high physical activity group in men.