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Monday, August 9, 2010
Mass. General study may lead to techniques to enhance sleep, improve hospital care
People who have trouble sleeping in
noisy environments often resort to strategies like earplugs or noise-canceling
headphones that muffle the sound, but a new study from investigators at
Massachusetts General Hospital (MGH) may lead to ways to block disturbing
sounds within the brain. In their report
in the August 10 issue of Current Biology,
the team reports finding a brain-wave pattern, reflecting activity of a key
structure, that predicts the ease at which sleep can be disrupted by noise.
"We wanted to investigate what
the brain does to promote stable sleep, even in the face of noise, and why some
people are better at staying asleep than others," explains Jeffrey
Ellenbogen, MD, chief of the MGH Division of Sleep Medicine. "Understanding the tools and techniques
the brain naturally uses could help us harness and expand those responses to help
stay asleep in noisy environments."
Upon entering the brain, most
sensory information, including sound, passes through a deep-brain structure
called the thalamus on its way to the cortex where signals are perceived. Communication between these structures
continues during sleep and is reflected by fluctuations in the brain's
electrical field, producing rhythmic patterns detected through
electroencephalography (EEG). Typical
EEG patterns are used to distinguish stages of sleep, and in the second and
third stages, slow brain wave patterns are interspersed with brief, rapid
pulses called spindles.
Previous research suggested that brain
activity producing spindles, which only appear during sleep, also keeps sensory
information from passing through the thalamus, a hypothesis the current study
was designed to test. The team enrolled
12 healthy, adult volunteers, each of whom spent three consecutive nights in
the MGH sleep lab. EEG reading were
taken throughout each night, the first of which was quiet. During the next two nights, participants were
regularly subjected to increasing levels of noise until their EEGs indicated
they were no longer asleep.
Analyzing the results revealed that
each participant maintained a consistent, night-to-night spindle rate and that
those with higher rates on the quiet night were less likely to be aroused on the
noisy nights. Participants often were
not aware that their sleep had been interrupted, Ellenbogen notes, indicating
that environmental noise can have a greater impact on sleep quality than an
individual may realize.
"We were surprised by the
magnitude of the effect," he explains.
"We designed the study to follow participants for three nights to
capture a lot of data, but the effect was so pronounced that we could see it
after a single 'noisy' night. Now we want
to study behavioral techniques, drugs or devices that may enhance sleep
spindles and see if they can help people stay asleep when confronted with noise
and maintain otherwise healthy, natural sleep."
An assistant professor of Neurology
at Harvard Medical School,
Ellenbogen hopes this work will be particularly helpful to hospital patients,
who are under stress and need quality sleep but are surrounded by often-noisy
equipment. "We need to work with
hospitals around the country to develop solutions, targeting sounds like alarms
to the people who need to hear them and not those who don't. Brain-based solutions like enhancing sleep
spindles will likely have a role in these strategies."
Lead author of the Current Biology article is Thien Thahn
Dang-Vu, MD, PhD, MGH Neurology.
Additional co-authors are Scott McKinney, MGH Neurology: Orfeu Buxton, PhD,
Brigham and Woman's Hospital; and Jo Solet, PhD, Cambridge Health Alliance. The study was supported by grants from the Academy of Architecture for Health, the Facilities
Guidelines Institute and the Centre for Health Design.
established in 1811, is the original and largest teaching hospital of Harvard Medical School.
The MGH conducts the largest hospital-based research program in the United States,
with an annual research budget of more than $600 million and major research
centers in AIDS, cardiovascular research, cancer, computational and integrative
biology, cutaneous biology, human genetics, medical imaging, neurodegenerative
disorders, regenerative medicine, systems biology, transplantation biology and
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