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expert reaction to study on physical activity, sedentary behaviour and bowel cancer risk

The British Journal of Cancer has published a study that examines the association between sedentary behaviour and increased bowel cancer risk in men.


Prof Paul Pharoah, Professor of Cancer Epidemiology, University of Cambridge, said:

“This study is an analysis of UK Biobank data to investigate the association between physical activity and risk of bowel cancer.  It is very important to note that association does not mean causation – the quote from Prof Bauld “This study poses interesting questions such as why screen time from computers didn’t increase the risk of bowel cancer but watching TV did” is somewhat misleading because this study has not demonstrated that watching TV increases the risk of bowel cancer, it has demonstrated that time spent watching TV is associated with risk of bowel cancer.

“The findings from this study are not novel.  It has long been known that physical activity is associated with a reduced risk of colon cancer, and this study confirms this association.

“The association with time spent watching TV and time in front of a computer screen are difficult to interpret.  These behaviours are strongly associated/correlated with other behaviours, such as diet, which may well explain the association with bowel cancer risk.  If sedentary behaviour were the explanation for the association with TV time, as speculated by the authors, then it would not depend on the cause of the sedentary behaviour.

“There were some differences in the observed associations between men and women, but these differences were small and the most likely explanation is that they are chance findings.

“In short the implication of this study for individuals is nothing very new.  We already know that eating a healthy diet, maintaining a healthy body weight, keeping active, limiting alcohol intake and not smoking reduces the risk of many diseases.”


* ‘Physical Activity, Sedentary Behaviour and Colorectal Cancer Risk in the UK Biobank’ by Jessica Morris et al. published in British Journal of Cancer on Friday 9th March. 


All our previous output on this subject can be seen at this weblink:


Declared interests

Prof Paul Pharoah: I have no conflicts of interest to declare.


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