Lack of physical activity has been long been linked with diabetes, obesity and cardiovascular disease but a new study suggests that it can also increase the risk of certain types of cancer.
Researchers from the Department of Epidemiology and Preventive Medicine at the 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. They looked at the relationship between TV viewing time, recreational sitting time, occupational sitting time, and total sitting time and the risk of various cancers.
When the highest levels of sedentary behaviour were compared to the lowest, the researchers found a statistically significantly higher risk for three particular types of cancer, namely, colon cancer, endometrial cancer, and lung cancer. Furthermore, the risk increased with each 2-hour increase in sitting time, 8% for colon cancer, 10% for endometrial cancer, and 6% for lung cancer. 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, because TV watching is often associated with consuming junk food.
The researchers conclude that the fact that sedentary behaviour has a detrimental impact on cancer even among people who are physically active implies that limiting the amount of time spent sitting down may play an important role in preventing cancer.
The study is published in the Journal of the National Cancer Institute.
