Sitting down for too long increases the risk of certain cancers, as well as heart disease and diabetes, a new analysis suggests.
Every extra two hours spent sitting down was associated with an 8% increase in the risk of bowel and a 6% increase in the risk of lung cancer.
Even in people with active lifestyles, it appears that those who spend a long time sitting were vulnerable to a heightened risk of cancer.
Scientists came to the conclusion after analysing pooled data from 43 studies involving more than four million participants and almost 70,000 cancer cases.
This kind of research, known as “meta-analysis”, can uncover trends that might be hidden from individual studies recruiting small numbers of people.
All the studies analysed involved questionnaires and interviews probing lifestyle habits related to activity such as TV viewing time, sitting time at home and at work, and total sitting time.
Comparing the highest and lowest levels of sedentary behaviour revealed a statistically significant increased risk for three specific cancers – bowel, endometrial (womb lining) and lung.
Study authors Daniela Schmid and Dr Michael Leitzmann, from the University of Regensburg in Germany, wrote in the Journal of the National Cancer Institute: “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.”
TV viewing time was most strongly associated with bowel and endometrial cancers, possibly because watching TV is often accompanied by eating junk food and drinking sweetened beverages, said the researchers.
The scientists pointed out that the link between sitting time and lung cancer was only marginally statistically significant.