GENE MUTATION LINKED TO SHORT SLEEP DURATION
Researchers who
studied 100 twin pairs have identified a gene mutation that may allow the
carrier to function normally on less than six hours of sleep per night. The
genetic variant also appears to provide greater resistance to the effects of
sleep deprivation.
Results show that a
participant with p.Tyr362His -- a variant of the BHLHE41 gene -- had an average
nightly sleep duration of only five hours, which was more than one hour shorter
than the non-carrier twin, who slept for about six hours and five minutes per
night. The twin with the gene mutation also had 40 percent fewer average lapses
of performance during 38 hours without sleep and required less recovery sleep
afterward -- sleeping only eight hours after the period of extended sleep
deprivation compared with his twin brother, who slept for 9.5 hours.
According to the
authors, this is only the second study to link a mutation of the BHLHE41 gene
-- also known as DEC2 -- to short sleep duration. The study provides new
insights into the genetic basis of short sleep in humans and the molecular
mechanisms involved in setting the duration of sleep that individuals need.
"This work
provides an important second gene variant associated with sleep deprivation and
for the first time shows the role of BHLHE41 in resistance to sleep deprivation
in humans," said lead author Renata Pellegrino, PhD, senior research
associate in the Center for Applied Genomics at The Children's Hospital of
Philadelphia. "The mutation was associated with resistance to the
neurobehavioral effects of sleep deprivation."
Study results are published
in the Aug. 1 issue of the journal Sleep.
The study group
comprised 100 twin pairs -- 59 monozygotic pairs and 41 dizygotic pairs -- who
were recruited at the University of Pennsylvania. All twin pairs were the same
sex and were healthy with no chronic conditions. Nightly sleep duration was
measured at home by actigraphy for seven to eight nights. Response to 38 hours
of sleep deprivation and length of recovery sleep were assessed in a sleep lab.
During sleep deprivation, cognitive performance was measured every two hours
using the Psychomotor Vigilance Test.
Although individual
sleep needs vary, the American Academy of Sleep Medicine recommends that adults
get about seven to nine hours of nightly sleep. However, a small percentage of
adults are normal short sleepers who routinely obtain less than six hours of
sleep per night without any complaints of sleep difficulties and no obvious
daytime dysfunction.
"This study
emphasizes that our need for sleep is a biological requirement, not a personal
preference," said American Academy of Sleep Medicine President Dr. Timothy
Morgenthaler. "Most adults appear to need at least seven hours of quality
sleep each night for optimal health, productivity and daytime alertness."
According to the AASM,
most people who regularly get six hours of sleep or less are restricting their
sleep and suffer from insufficient sleep syndrome, which occurs when an
individual persistently fails to obtain the amount of sleep required to
maintain normal levels of alertness and wakefulness. Data from the Centers for
Disease Control and Prevention indicate that 28 percent of U.S. adults report
sleeping six hours or less in a 24-hour period. Insufficient sleep results in
increased daytime sleepiness, concentration problems and lowered energy level,
and it increases the risk of depression, drowsy driving, and workplace
accidents.
The study involved a
collaboration between researchers from The Children's Hospital of Philadelphia;
Universidade Federal de São Paulo (UNIFESP) in São Paulo, Brazil; Koc
University in Istanbul, Turkey; the University of Pennsylvania Perelman School
of Medicine; the Philadelphia Veterans Affairs Medical Center; and Washington
State University. The research was supported in part by grants from the
National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of
Health (NIH), and the Institutional Development Fund from the Center for
Applied Genomics at The Children's Hospital of Philadelphia.
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