The short story: a lot. The long story: about 8.2 hours for adolescents and 6.4 hours for adults.
"Prolonged sitting, particularly watching television or videos, has been associated with increased risk of multiple diseases and mortality," the new study starts off. Indeed, research has linked sitting to issues such as increased blood pressure, high blood sugar, excess body fat and abnormal cholesterol levels -- to name just a few. The science is extremely clear on that, but although we know we should sit less, we really don't. I'm sitting as I'm writing this, and you're probably reading this sitting. Sitting has become so ingrained in our day to day life that not doing it almost feels like a chore.
In an attempt to see just how much Americans sit, researchers working in Canada and the US analyzed data from nearly 52,000 children, adolescents and adults from 2001-2016.
A majority of all investigated age groups spend an unhealthy amount of time sitting. The team found that 62% of children, 59% of adolescents and 65% of adults sat watching television or videos at least 2 hours a day in 2015-2016. But while the number of people sitting for more than 2 hours has remained relatively stable, the overall sitting time has increased. We're sitting more than ever before, researchers found.
Overall sitting time has increased from 7.0 to 8.2 h/d among adolescents and from 5.5 to 6.4 h/d among adults, and the main reason for that is the computer. Computer use outside school or work for at least 1 h/d increased from 2001 to 2016. Surprisingly, this growth has been most prevalent for adults.
"In this nationally representative survey of the US population from 2001 through 2016, the estimated prevalence of sitting watching television or videos for at least 2 hours per day generally remained high and stable. The estimated prevalence of computer use during leisure-time increased among all age groups, and the estimated total sitting time increased among adolescents and adults," the study reads.
Some groups tend to watch TV more than others, researchers also found.
"For all ages, a substantially higher prevalence of sitting watching television or videos was observed among male, non-Hispanic black, obese, or physically inactive individuals," the study continues, adding that black adults were at higher risk of all-cause mortality associated with prolonged television viewing than were white adults.
While having an active lifestyle can offset some of the damage done by sitting, it can't eliminate the risk completely. Public health programs typically focus on increasing physical activity rather than reducing sitting time and sitting time rarely plays a central role in health interventions.
The US isn't an isolated case. The world is experiencing a sitting epidemic, with previous research finding that sitting occupies up to half of an adult's workday in developed countries. However, the world still doesn't have a clear solution, particularly as alternatives such as standing desks are rather unpopular, and the health results associated with them have been mixed.
The study has been published in JAMA.