How Sitting Increases Cancer Risk
Modern man spends a lot of time sitting down, either while relaxing or at work. Some jobs involve long stretches of sitting down at a desk with little physical activity. Many people have recreational activities that also involve a lot of sitting — like watching television or using the Internet.
Researchers are just starting to understand the health ramifications of sitting down for many hours each day. Unfortunately it’s not good news, with a number of serious health risks associated with sitting. This article will out line some of the recent research into sedentary behavior and the health problems associated with it.
One research paper looked at the effect of sedentary behavior on rodents. One group of mice were allowed to perform exercise on gym equipment while the other were not. Researchers found that the mice who did not undertake exercise had structural changes in the neurons in their brains. Those neurons were responsible for regulating cardiovascular function. It is thought that the changes to these neurons contribute to cardiovascular disease (Mischel NA, Llewellyn-Smith IJ, Mueller PJ, 2014).
In a meta-analysis of 43 observational studies involving more than 4 million people, it was found that sedentary behavior greatly increased cancer risk (Schmid D,Leitzmann MF, 2014). Researchers found that the risk of lung, colon and endometrial cancers was significantly increased by sedentary behavior. The more a person sat down, the more their cancer risk increased. For every 2 hours of sedentary activity per day, lung cancer risk increased by 6%, colon cancer risk increased by 8% and endometrial cancer risk increased by 10%.
The Canadian cancer society suggests that the health impacts of sedentary behavior create other problems that lead to cancer (Cancer.ca, 2014). For example, most people who spend long periods sitting down gain weight. That weight gain can substantially increase the chances of getting cancer (Cancer.gov, 2014).
Sedentary behavior changes hormone levels which can also lead to some forms of cancer (Lynch BM, 2010). Sex hormones estrogen and androgen increase, which is linked to breast cancer in women and prostate cancer in men. Sex hormone binding globulin (SHBG) levels decrease because of inactivity. The decrease in SHBG is thought to play a role in breast cancer (Moore JW, Key TJ, Bulbrook RD, Clark GM, Allen DS, Wang DY, Pike MC, 1987).
The less active you are, the more likely it is that you will have high blood sugar, increased insulin levels and eventually insulin resistance. Some research has even indicated that regular exercise might not be enough to shield you from diabetes, if you spend a lot of time sitting down (Endocrineweb.com, 2011).
The production of enzymes that burn fat also drastically slow when you are sitting. One study found that there were 90% less fat burning enzymes in people sitting for an hour or more (NYTimes, 2012). Your metabolism also slows while sitting, potentially leading to weight gain and obesity.
Research has shown that the human brain performs better if it has a supply of fresh oxygenated blood (MedicalNewsToday, 2014). While sitting, your body is at rest and there is less fresh blood and oxygen reaching your brain.
One study demonstrated that people have better neuronal function within the brain while standing, as opposed to sitting (Ouchi Y, Okada H, Yoshikawa E, Nobezawa S, Futatsubashi M, 1998). Put simply, your brain is more alert when you are in standing instead of sitting.
Muscle and Bone Degeneration
Sitting down for long periods can lead to muscular degeneration, because you aren’t using many muscle groups while in that position. Your abdominal and back muscles are essentially unused while seated, worsening any back problems you may have. You leg muscles are mostly unused in the position also, leading to muscle loss there.
One study noticed that people who spent many hours sitting had a greater risk of osteoporotic hip fracture (Weiss M, Yogev R, Dolev E, 1998). This was due to low mineral density in the bones of people who spent a great deal of time sitting.
Sitting can also damage your posture and can change the natural curve of your spine (Mashable, 2012). Slipped discs are a common injury in people who spend a great deal of time seated. Some doctors suggest people should only be seated for a maximum of 20 minutes, to avoid back damage.
The research is clear — prolonged sitting can have a negative health impact which can shave years off your life. For people who are sitting all day, then going home for more sedentary activity like watching television, the problem is even worse. To enjoy a healthy life and avoid some particularly nasty health issues, stand as much as possible and keep moving!
Cancer.ca (2014). Sedentary behavior. cancer.ca/en/cancer-information/cancer-101/what-is-a-risk-factor/sedentary-behaviour/?region=on
Cancer.gov (2014). Obesity and Cancer Risk. cancer.gov/cancertopics/factsheet/Risk/obesity
Endocrineweb.com (2011). Sedentary lifestyles connected to type 2 diabetes. endocrineweb.com/news/type-2-diabetes/6750-sedentary-lifestyles-connected-type-2-diabetes
Lynch BM, (2010). Sedentary Behavior and Cancer: A Systematic Review of the Literature and Proposed Biological Mechanisms. cebp.aacrjournals.org/content/19/11/2691.full
Mashable (2012). Why Sitting Too Much Is Dangerous. mashable.com/2012/06/18/too-much-sitting/
MedicalNewsToday (2014). Sedentary behavior ‘may counteract brain benefits of exercise in older adults’. medicalnewstoday.com/articles/282745.php
Mischel NA, Llewellyn-Smith IJ, Mueller PJ (2014). Physical (in)activity-dependent structural plasticity in bulbospinal catecholaminergic neurons of rat rostral ventrolateral medulla. ncbi.nlm.nih.gov/pubmed/24114875
Moore JW, Key TJ, Bulbrook RD, Clark GM, Allen DS, Wang DY, Pike MC (1987). Sex hormone binding globulin and risk factors for breast cancer in a population of normal women who had never used exogenous sex hormones. ncbi.nlm.nih.gov/pmc/articles/PMC2001893/
NYTimes (2012). Taking a Stand for Office Ergonomics. http://www.nytimes.com/2012/12/02/business/stand-up-desks-gaining-favor-in-the-workplace.html?_r=0
Schmid D,Leitzmann MF (2014). Television Viewing and Time Spent Sedentary in Relation to Cancer Risk: A Meta-Analysis. jnci.oxfordjournals.org/content/106/7/dju098.full
Ouchi Y, Okada H, Yoshikawa E, Nobezawa S Futatsubashi M (1998). Brain Activation During Maintenance Of Standing Postures In Humans. brain.oxfordjournals.org/content/122/2/329.full
Weiss M, Yogev R, Dolev E (1998). Occupational sitting and low hip mineral density. ncbi.nlm.nih.gov/pubmed/9405733