Physical inactivity has been linked with diabetes, obesity, and cardiovascular disease, but it can also increase the risk of certain cancers, according to a study published June 16 in the JNCI: Journal of the National Cancer Institute. To assess the relationship between TV viewing time, recreational sitting time, occupational sitting time, and total sitting time with the risk of various cancers, Daniela Schmid, PhD and Dr Michael Leitzmann of the Department of Epidemiology and Preventive Medicine, University of Regensburg, Germany, conducted a meta-analysis of 43 observational studies, including over 4 million individuals and 68,936 cancer cases. Data in the individual studies had been obtained with self-administered questionnaires and through interviews.
When the highest levels of sedentary behavior were compared to the lowest, the researchers found a statistically significant higher risk for three types of cancer—colon, endometrial, and lung.
Moreover, the risk increased with each 2-hour increase in sitting time, 8% for colon cancer, 10% for endometrial cancer, and 6% for lung cancer, although the last was borderline statistically significant.
The effect also seemed to be independent of physical activity, suggesting that large amounts of time spent sitting can still be detrimental to those who are otherwise physically active.
TV viewing time showed the strongest relationship with colon and endometrial cancer, possibly, the authors write, because TV watching is often associated with drinking sweetened beverages, and eating junk foods.
The researchers write "That sedentariness has a detrimental impact on cancer even among physically active persons implies that limiting the time spent sedentary may play an important role in preventing cancer…".
In an accompanying editorial, Lin Yang and Dr Graham A. Colditz of the Siteman Cancer Center and Department of Surgery, Washington University School of Medicine, St. Louis MO, write that these results "…support a causal relation between sedentary behavior and both colon and endometrial cancers." They comment that cancer prevention requires good evidence, political will, and a social strategy to fund and implement prevention programmes.
Making diet count in cancer prevention
Cancer risk factors can be reduced by correct nutrition and physical activity, which are key elements in all recommendations for cancer prevention, such as the European code against cancer.
In a recently published report, Joint Research Center (JRC), Institute for Health and Consumer Protection scientists screened the national cancer plans of all EU Members States plus Iceland, Norway, Switzerland and Turkey and checked how much attention was given to the dietary prevention of cancer.
The analysis revealed that over 90% of the plans acknowledge a general link between nutrition and/or physical activity, and the potential positive impact that these can have in the prevention of various types of cancer.
However, when looking into the contents and focal areas of the documents, differences appear. The majority of the actions targeting diets and physical activity consist of awareness-raising campaigns. More binding, concrete measures to make healthy options easily available, or to influence behaviour change towards healthier lifestyles and dietary patterns are less frequent. For example, only 9 national cancer plans provide actions targeting consumption of fruit and vegetables beyond purely providing information on their beneficial effects.
The JRC report "Mapping dietary prevention of cancer in the EU" aims at promoting stronger inclusion of dietary prevention of cancer in plans throughout Europe. The authors calls on all actors to share best practices and results in the joint endeavour to reduce the economic burden of cancer, which in 2010 alone was estimated at 166 billion EUR and represents the second most common cause of death in the EU. Diet-related actions to fight cancer are cost-effective and efficient strategies to cut healthcare costs. Investments in dietary prevention measures can not only reduce cancer rates but also the risk of other non-communicable diseases, such as type II diabetes and cardiovascular disease.
Schmid D, Leitzmann MF. Television Viewing and Time Spent Sedentary in Relation to Cancer Risk: A Meta-analysis. JNCI J Natl Cancer Inst 2014; 106 (7): dju098 doi: 10.1093/jnci/dju098.
Yang L, Colditz GA. An Active Lifestyle for Cancer Prevention. JNCI J Natl Cancer Inst 2014; 106 (7): dju135 doi: 10.1093/jnci/dju135