Reducing total daily sitting time to less than three hours can increase life expectancy by two full years, claims a new study.

Researchers at Louisiana State University (LSU; Baton Rouge, USA) and Brigham and Women's Hospital (BWH; Boston, MA, USA) conducted a meta analysis via life table analysis based on the prevalence of sedentary behavior obtained from the US National Health and Nutrition Examination Survey (NHANES) from the 2009-2010 survey for sitting and the 2005-2006 study for TV viewing. The researchers then evaluated relative risks (RRs) of all-cause mortality. The cohorts included a combined 166,738 respondents followed for an average 9.28 years.

The analysis showed that the pooled RR for sitting and all-cause mortality was 1.45 for those who spent the most time sitting, versus those who spent the least. For associations between television viewing and all-cause mortality, the pooled RR was 1.49 for those who watched the most television compared to those who watched the least. Gains in life expectancy for sitting (two years) and television viewing (1.38 years) came from adjustment from the amounts of time spent on the sedentary behaviors compared to the lowest range. The study was published on July 9, 2012, in BMJ Open.

“A number of mechanisms could explain the association of sedentary behaviors and mortality, including increased risk of type two diabetes and cardiovascular disease,” concluded study authors Peter Katzmarzyk, PhD, of LSU, and I-Min Lee, MD, of BWH. “Reducing sedentary behaviors such as sitting and television viewing may have the potential to increase life expectancy in the USA.”

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