As exercise increases, sleep decreases among those who wake up early
to work out before heading to their jobs, the study authors report
in the journal Sleep Health. At the same time, getting some exercise
versus none during the day also helped people to sleep better.
"Sleep research has focused on the ways that sleep deprivation
affects overall health, but at some point we began wondering what
people were doing with the time they weren't sleeping," said senior
study author Dr. Mathias Basner of the University of Pennsylvania
Perelman School of Medicine in Philadelphia.
The American Academy of Sleep Medicine and the Sleep Research
Society both recommend seven or more hours of sleep per night, yet
more than a third of adults in the U.S. say they sleep less than
that.
"We all have 24 hours in a day, so for the people who only sleep
five or six hours, are they doing a healthy behavior or sitting in
front of the TV eating chips?" Basner said in a phone interview.
"We've been trying to identify activities that could be traded for
more sleep."
Basner and colleagues analyzed American Time Use Survey data for
nearly 48,000 working men and women interviewed on a weekday between
2003 and 2016. As part of the survey, participants logged how they
spent their time in the previous 24 hours.
Researchers found that people spent most of their time working and
commuting. About 17 percent said they had exercised in the last 24
hours. Overall, long work hours were associated with both short
sleep and low exercise rates. At the same time, those who exercised
slept an average of 15 minutes less than those who didn't. In fact,
sleep time dropped as exercise time increased.
The strongest association between exercise and sleep was seen among
people who exercised between 6 a.m. and 8 a.m. or between 9 p.m. and
11 p.m. Exercise for up to an hour either in the morning or the
evening was not associated with significantly shorter sleep.
"The problem is, we can't tell people to work less, but we can look
at habits before bed, which is usually TV watching, or in the
morning, which is commuting and grooming," Basner said. "This study
suggests it's possible to both exercise and get enough sleep."
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Basner and colleagues were surprised to find that in contrast to
previous advice about not exercising before bed, those who got
physical activity later at night seemed to still get plenty of
sleep. Instead of harming sleep, exercising during the day, even if
close to bedtime, might help people to sleep more deeply or fall
asleep sooner, he said.
"This probably depends on personality, too, and whether someone has
an early or late circadian preference," he added. "An owl who is
likely to go to bed at 1 a.m. might exercise well at night, and the
lark who wakes up at 5 a.m. anyway might exercise before work."
Family income and education levels influenced sleep time as well.
Generally, those who earn more and have higher education tend to get
less sleep, but they're also more likely to exercise. Although this
study was based in the U.S., Basner speculates the same would apply
in other developed countries.
"There is the impression that we are pressed for time now more than
ever. This is probably due, in part, to exposure to more
time-wasting things like social media, nevertheless, clearly for
many people there is a perceived choice between healthy behaviors,"
said Shawn Youngstedt, a researcher at Arizona State University in
Tempe who wasn't involved in the study.
A limitation of using American Time Use Survey data to study
exercise and sleep, he said, is that "sleep" includes lying in bed
and resting, which could skew the results.
At the same time, he said by email, "This advances an excellent idea
to try to promote exercise at times in which it does not curtail
sleep. Offering exercise opportunities at work would probably
facilitate healthy and more productive workers."
SOURCE: https://bit.ly/2Q6qqlD Sleep Health, online October 25,
2018.
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