If you do not snooze you lose: sleep seen as essential for the brain
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[September 21, 2020]
By Will Dunham
WASHINGTON (Reuters) - Scientists are
providing a fuller understanding of the essential role that sleep plays
in brain health, identifying an abrupt transition at about 2.4 years of
age when its primary purpose shifts from brain building to maintenance
and repair.
Researchers on Friday said they conducted a statistical analysis on data
from more than 60 sleep studies. They looked at sleep time, duration of
rapid eye movement (REM) sleep, brain size and body size, and devised a
mathematical model for how sleep changes during development.
There are basically two types of sleep, each tied to specific brain
waves and neuronal activity. REM, with the eyes moving quickly from side
to side behind closed eyelids, is deep sleep with vivid dreams. Non-REM
sleep is largely dreamless.
During REM sleep, the brain forms new neural connections by building and
strengthening synapses - the junctions between nerve cells, or neurons -
that enable them to communicate, reinforcing learning and consolidating
memories. During sleep, the brain also repairs the modicum of daily
neurological damage it typically experiences to genes and proteins
within neurons as well as clearing out byproducts that build up.
At about 2.4 years of age, the findings showed, sleep's primary function
changed from building and cutting connections during REM sleep to neural
repair during both REM and non-REM sleep.
"It was shocking to us that this transition was like a switch and so
sharp," said Van Savage, a UCLA professor of ecology and evolutionary
biology and of computational medicine who is a senior author of the
research published in the journal Science Advances.
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A girl sleeps while waiting for the arrival of Pope Francis at St.
Peter’s Parish church in the Sam Phran district of Nakhon Pathom
Province, Thailand, November 22, 2019. REUTERS/Jorge Silva/File
Photo
REM sleep declines with age. Newborns, who can sleep about 16 hours
daily, spend about 50% of their sleeping time in REM, but there is a
pronounced drop-off at around 2.4 years. It drops to about 25% by
age 10 and to about 10% to 15% around age 50.
"Sleep is required across the animal kingdom and is nearly as
ubiquitous as eating and breathing," Van Savage said. "I'd say it is
a pillar of human health."
(Reporting by Will Dunham; editing by Jonathan Oatis)
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