|
 People may also be less likely to die young if they break up
sedentary time by moving around every half hour than if they remain
seated for longer stretches of time without getting up, the study
also suggests.
“We think these findings suggest that it is simply not enough to be
active or move at just one specific time of the day, that is,
exercise,” said lead study author Keith Diaz of the Center for
Behavioral Cardiovascular Health at Columbia University Medical
Center in New York.
“We need to be mindful of moving frequently throughout the day in
addition to exercising,” Diaz said by email.
While previous research has linked excessive sedentary time to an
increased risk of death, many of these studies relied on people to
accurately recall and report how much they moved around and might
not have painted a clear picture of the relationship between
mortality and inactivity.
For the current study, researchers examined data on 7,985 adults,
age 45 and older, who were asked to wear accelerometers to measure
activity levels for one week.
Overall, sedentary behavior accounted for 77 percent of
participants’ waking hours, or about 12 hours a day, researchers
report in the Annals of Internal Medicine.
On averages, bouts of sedentary time were about 11 minutes long, and
more than half of the time people spent sitting and standing
happened in bouts of less than 30 minutes, the study found.
About 14 percent of the people in the study typically had stretches
of sedentary time lasting at least 90 minutes, however.
During the study, 340 people died after an average follow-up of four
years.
Researchers sorted participants into four groups from the least
sedentary people, who spent only about 11 hours total sitting and
standing in a typical day, to the most sedentary people who were
inactive for more than 13 hours a day.
They also sorted participants into four groups based on how long
typical bouts of sedentary time lasted before people took movement
breaks, ranging from less than 7.7 minutes to at least 12.4 minutes.
Compared to the least sedentary people with the briefest stretches
of sitting time, the most sedentary people with the longest periods
of sitting down were twice as likely to die of all cause during the
study period.
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One limitation of the study, however, is that the accelerometers
couldn’t distinguish between sedentary time from sitting versus
inactive periods when people were standing, the authors note.
The study also wasn’t a controlled experiment designed to prove how
or whether sedentary time directly causes premature death.
It’s possible that prolonged sedentary stretches might hasten death
by causing what’s known as metabolic toxicity, said Dr. David Alter,
head of cardiovascular and metabolic research for the University
Health Network-Toronto Rehabilitation Institute in Canada.
“The lack of activity in our muscles affects our ability to
metabolize our sugars efficiently,” Alter, author of an accompanying
editorial, said by email. “Over time, our body accumulates excess
fat, which can lead to obesity, diabetes, heart disease, cancer and
death.”
One thing that might help, however, is a stopwatch, because it could
remind people to get up and move around often throughout the day and
avoid long stretches of sedentary time, Alter said.
Even though standing desks have become increasingly popular as a
possible fix to the problems caused by sedentary time, it’s not
clear if they help people live longer.
“Anything that will facilitate movement would be better: treadmill
desks, under desk steppers or cycles, or just plain old fashioned
walking breaks that can be pretty easily implemented in an office
setting,” Diaz said.
SOURCE http://bit.ly/2wUY5CT Annals of Internal Medicine, online
September 11, 2017.
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