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 Sleep deprivation can have a negative impact on brain function,
metabolism, hormones and the immune system. While research has shown
that a 30-minute afternoon nap can restore alertness, the current
study is the first to examine whether napping has any impact on
stress or immune system function, said Brice Faraut, a sleep
researcher at Université Paris Descartes-Sorbonne Paris Cité in
France.
Faraut and colleagues studied 11 healthy young men who typically
slept seven to nine hours each night, didn’t smoke and didn't
normally take naps.
Two separate times, each man participated in a three-day session of
sleep tests in a laboratory where food intake and lighting were
strictly controlled and no alcohol, caffeine or medications were
allowed.
During one session, they slept normally for one night but then were
only allowed to sleep for two hours the next night. The men could
sleep as much as they liked on the third night.
The other session was the same - except the men were allowed to take
two 30-minute naps the day after their sleep was restricted.
The study team collected urine and saliva samples each day to
measure levels of norepinephrine, a substance that's typically
released when the body is under stress. It increases heart rate,
constricts blood vessels and raises blood pressure and blood sugar.
The men’s norepinephrine levels were more than doubled in the
afternoon after the night of sleep restriction, compared to the day
after they had slept normally. But there was no change in
norepinephrine when participants were allowed to nap.
Lack of sleep also affected an immune-regulating molecule called
interleukin-6, which dropped when the men were sleep-deprived but
stayed normal when they were allowed to nap.
This relatively short nap duration can be a "powerful countermeasure
to sleep debt," Faraut said in an email, adding that the findings
need to be tested in real-life situations.
Michael Grandner, a sleep researcher at the University of
Pennsylvania who was not involved in the study, said the immune
findings were somewhat contradictory to the existing literature.
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“But these are complicated processes, and studies like these, that
examine what happens during partial recovery, (help) us understand
all of the ways that sleep is important for health and functioning,”
Grandner told Reuters Health by email.
Grandner differentiates between two types of napping.
“First are naps that you take because you are so exhausted that you
cannot stay awake,” Grandner said. “A nap in this case may help a
little, but being that exhausted is a sign of insufficient sleep or
a sleep disorder and it's unlikely that the nap can completely fix
the problem.”
“You might have a sleep disorder like sleep apnea (which is a very
common cause of sleepiness) or you may be sleep deprived," he said,
"which has been shown to be an important risk factor for weight gain
and obesity, heart disease, poor performance, and many other
outcomes.”
Grandner said the second type of nap is one you take to refresh
yourself.
“Rather than a nap by necessity, this is a nap by choice,” he said.
“These naps, since they are not in the context of exhaustion, have
the opportunity of boosting your performance (rather than simply
making up for lost sleep).”
SOURCE: http://bit.ly/1CF4kra Journal of Clinical Endocrinology and
Metabolism, online February 10, 2015.
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