Adolescents sit for an average of 8.2 hours a day, and adults sit for an average of 6.4 hours — about an hour more for both groups than a decade ago, the study reports.
That extra hour is mostly spent in front of a computer screen, the study also found.
This trend is troubling, as prolonged sitting has been linked with an increased risk of obesity, heart disease, cancer, type 2 diabetes and early death.
And don’t think that getting up for an occasional short walk will offset that sitting time. As another study, published this week in the Journal of the American College of Cardiology, reports, the negative health risk from prolonged sitting is eliminated entirely only among people who are highly active — who engage in at least five hours of moderate to vigorous exercise per week.
“Everything we found is concerning,” Yin Cao, the senior author of the JAMA study and a researcher at Washington University in St. Louis, told the Associated Press. “The overall message is prolonged sitting is highly prevalent.”
Television time: high but steady
For the study, Cao and her colleagues analyzed data collected from more than 51,000 people who participated in the National Health and Nutrition Examination Survey (NHANES) between 2001 and 2016. The survey’s questions deal with a long list of health-related risk factors, including the amount of time spent engaged in sedentary behaviors, such as sitting in front of a TV or computer screen.
The researchers looked at four age groups: children aged 5 to 11 (whose data came from a parent or guardian), teens aged 12 to 19, adults aged 20 to 64, and adults aged 65 and older.
The data showed that from 2007 to 2016 the average total daily sitting time (including at work and at school) increased from 7.0 to 8.2 hours per day for teens and from 5.5 hours to 6.4 hours per day for adults. (The survey did not capture data on the total sitting time of children.)
A substantial proportion of Americans spend at least two hours of their leisure (non-work and non-school) time each day watching television or videos: 62 percent of children, 59 percent of adolescents, 62 percent of adults aged 20 to 64, and 84 percent of adults aged 65 and older.
Across all age groups, 28 percent to 38 percent of Americans spend three hours or more each day in front of a television screen, and 18 percent to 23 percent spend four or more hours.
Computer time: on the rise
Although those television-viewing numbers are high, they have held steady over the past decade — except for among older adults, whose TV time has risen by about 3.5 percent since 2007.
The same can’t be said for computer time, however. The study found that the amount of leisure time Americans spend sitting in front of a computer screen has gone up across all age groups.
In 2001, 43 percent of children used a computer outside of the classroom for one hour or more per day — a number that jumped to 56 percent in 2016. The proportion of teens who spend an hour or more of their leisure time in front of a computer increased more slowly, from 53 percent in 2003 to 57 percent in 2016, while the proportion of adults who do so leaped from 29 percent to 50 percent.
Today, more than half of Americans use a computer during their leisure time for more than an hour a day, while up to a quarter use it for three or more hours per day.
A need for change
“In almost none of the groups we analyzed are the numbers going in the right direction,” says Cao in a released statement. “We want to raise awareness about this issue on multiple levels — from individuals and families to schools, employers and elected officials.”
She and her colleagues believe that, as a society, we need to be developing daily activities, routines and habits that involve less sitting.
“We think a lot of these sedentary habits are formed early, so if we can make changes that help children be more active, it could pay off in the future, both for children as they grow to adulthood and for future health-care spending,” explains Dr. Graham Colditz, one of the study’s co-authors and a chronic disease epidemiologist at Washington University.
“How we create public policies or promote social change that supports less sitting is unclear and likely to be complicated,” he acknowledges. “If a neighborhood in a disadvantaged community is unsafe, for example, parents can’t just send their kids outside to play. Our environments — the way our cities, our school days and working days are designed — play roles in this behavior that are difficult to change.”
“But at least now, we have a baseline from which to measure whether specific changes are having an impact,” he adds.
FMI: You’ll find an abstract of the study on JAMA’s website, but the full study is behind a paywall.