Prolonged sitting results in a sedentary lifestyle and physical inactivity. Many workers in the United States and other countries sit for very long work hours during the day at a desk using a keyboard and computer. In addition, when we come home from work we often sit in front of a television which continues the physical inactivity. We have previously discussed the health risks associated with physical inactivity, and the finding that physical inactivity is equivalent to the health risks of smoking and obesity. Physical inactivity is a known risk factor for health problems such as coronary artery disease, type 2 diabetes, and some forms of cancer. Prolonged sitting and physical inactivity has contributed to the growing obesity epidemic in the United States and abroad. The World Health Organization has recommended 150 minutes per week of moderate exercise for adults that can take the form of brisk walking or light jogging. Despite this recommendation, many people do not engage in any physical activity, and the ones who do are not participating enough.
Recent research performed by Dr. Peter Katzmarzyk and Dr. I-Min Lee has shown that prolonged sitting and extended television watching decreases life expectancy by a significant degree and that decreasing both of these activities can potentially increase the life expectancy of the United States population. The results of their study were published in the journal BMJ Open. In performing their study, the researchers aimed to determine the impact of sitting and television viewing on the life expectancy of the US population. The research study was designed to use a meta-analysis to analyze all cause mortality due to sitting and prolonged television viewing. The study findings showed that the life expectancy in the US would be 2.0 years greater if the time that was spent sitting by adults was reduced to less than 3 hours per day, and 1.38 years greater if television viewing was decreased to less than 2 hours per day. This finding was also applicable to those individuals who participate in physical activity such as at a gym, but also sit for prolonged periods of time at work.
The authors wrote, “The results of this study indicate that limiting sitting to <3 h/day and limiting television viewing to <2 h/day may increase life expectancy at birth in the USA by approximately 2.0 and 1.4 years, respectively, assuming a causal relationship… There are several potential mechanisms that could explain the association between sedentary behaviour and all-cause mortality rates. Sedentary behaviour is associated with an increased risk of the development of chronic conditions such type 2 diabetes and cardiovascular disease… a significant shift in behavior change at the population level is required to make demonstrable improvements in life expectancy”.
The results of this study add to the growing body of data that points to the negative health effects of physical inactivity, prolonged sitting, and extended television viewing, which all ultimately result in a sedentary lifestyle. This study gives us an exact number that can be quoted for the decrease in life expectancy from prolonged sitting and extended television watching. Future studies should focus on determining the proper interventions that are needed to decrease our sedentary lifestyle and decrease the negative impact of prolonged sitting on life expectancy in the United States.
Peter T Katzmarzyk, I-Min Lee “Sedentary behavior and life expectancy in the USA: a cause-deleted life table analysis” BMJ Open 2012;2:e000828 doi:10.1136/bmjopen-2012-000828