Similarly, cutting down TV time to less than two 2 hours daily might extend life by almost 1.4 years. Several previous studies have linked extended periods spent sitting down and/or watching TV to poor health, such as diabetes and death from heart disease/stroke.
The researchers used data collected for the National Health and Nutrition Examination Survey (NHANES) for 2005/6 and 2009/10, to calculate the amount of time US adults spent watching TV and sitting down on a daily basis, the online journal BMJ Open reports.
NHANES regularly surveys a large representative sample of the US population on various aspects of their health and lifestyle, according to a NHANES statement.
They trawled the research database MEDLINE, looking for published studies on sitting time and deaths from all causes, and pooled the different relative risk data from the five relevant studies, involving almost 167,000 adults. The database was then re-analysed, taking account of age and sex.
They combined these data and the NHANES figures to come up with a population attributable fraction (PAF) an estimate of the theoretical effects of a risk factor at a population, rather than an individual level to calculate the number of deaths associated with time spent sitting down. The PAFs for deaths from all causes linked to sitting time and TV viewing were 27 percent and 19 percent, respectively.
The results of life table analyses indicates that cutting the amount of time spent sitting down every day to under three hours would add an extra two years to life expectancy. Similarly, restricting time spent watching TV to under two hours daily would extend life expectancy by an extra 1.38 years.
"The results of this study indicate that extended sitting time and TV viewing may have the potential to reduce life expectancy in the US," write study authors.