Graphic Brain Scans Shows Memory Loss from Sleep
Apnea
Scans reveal dwindling of brain structures that store
memory
Brain scans reveal that the
mammillary bodies of a sleep apnea patient (right) are smaller
than those of a control subject (left). Click photo for larger
view.
June 11, 2008 - UCLA researchers say they are the
first to discover that people with sleep apnea show tissue loss in brain
regions that help store memory. Reported in the June 27 edition of the
journal Neuroscience Letters, the findings emphasize the importance of
early detection of the disorder, which afflicts an estimated 20 million
Americans, with older men the most likely victims.
Those at the highest risk of sleep apnea are men,
overweight and over 40, but sleep apnea can strike anyone at any age,
according to the American Sleep Apnea Association.
Sleep apnea occurs when a blocked airway repeatedly
halts the sleeper's breathing, resulting in loud bursts of snoring and
chronic daytime fatigue. Memory loss and difficulty focusing are also
common complaints. Prior studies have linked the disorder to a higher
risk of stroke, heart disease and diabetes.
"Our findings demonstrate that impaired breathing
during sleep can lead to a serious brain injury that disrupts memory and
thinking," said principal investigator Ronald Harper, a distinguished
professor of neurobiology at the David Geffen School of Medicine at
UCLA.
The study focused on structures called mammillary
bodies, so named because they resemble small breasts, on the underside
of the brain.
The UCLA team scanned the brains of 43 sleep apnea
patients, using magnetic resonance imaging (MRI) to collect
high-resolution images of the entire brain, including slices of the
mammillary bodies.
The structures' small size and proximity to bone
and fluid make them difficult to measure by conventional MRI. So the
researchers manually traced the mammillary bodies from the
high-resolution scans and calculated their volumes from the hand-drawn
outlines.
When they compared the results to images of 66
control subjects matched for age and gender, the scientists discovered
that the sleep apnea patients' mammillary bodies were nearly 20 percent
smaller, particularly on the left side.
"The findings are important because patients
suffering memory loss from other syndromes, such as alcoholism or
Alzheimer disease, also show shrunken mammillary bodies," said lead
author Rajesh Kumar, a UCLA assistant researcher in neurobiology.
"Physicians treat memory loss in alcoholic patients
with massive amounts of thiamine, or vitamin B1," he added. "We suspect
that the dose helps dying cells to recover, enabling the brain to use
them again."
The scientists' next step is to determine how sleep
apnea causes tissue loss in the mammillary bodies.
Harper hypothesizes that repeated drops in oxygen
lead to the brain injury. During an apnea episode, the brain's blood
vessels constrict, starving its tissue of oxygen and causing cellular
death. The process also incites inflammation, which further damages the
tissue.
"The reduced size of the mammillary bodies suggests
that they've suffered a harmful event resulting in sizable cell loss,"
Harper said. "The fact that patients' memory problems continue despite
treatment for their sleep disorder implies a long-lasting brain injury."
In a future study, Harper and Kumar will explore
whether taking supplemental vitamin B1 helps restore sleep apnea
patients' memory. The vitamin helps move glucose into the cells,
preventing their death from oxygen starvation.
"UCLA researchers used sophisticated imaging
technology to identify brain lesions associated with impaired memory in
individuals with obstructive sleep apnea," said Elizabeth G. Nabel,
director of the National Heart, Lung and Blood Institute, which funded
the study. "These results underscore the importance of early diagnosis
and treatment of sleep-disordered breathing, which can have long-term
effects on patients' health and well-being."
Check
your Snore Score to see if you have sleep apnea
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American Sleep Apnea
Association
Obstructive sleep apnea occurs when the muscles in
the throat, soft palate and tongue relax during sleep and sag, narrowing
the airway. The tongue slides to the back of the mouth, blocking the
windpipe and cutting off oxygen to the lungs.
The sleeper wakes up, gasping for air, and falls
back into a fitful sleep. The cycle can repeat itself hundreds of times
per night.
Study co-authors included Bramley Birrer, Paul
Macey, Mary Woo and Frisca Yan-Go of UCLA, and Rakesh Gupta from the
Sanjay Gandhi Institute of Medical Sciences, India.
About Sleep Apnea
Sleep
apnea is a common disorder that can be serious. In sleep apnea, your
breathing stops or gets very shallow. Each pause in breathing typically
lasts 10 to 20 seconds or more. These pauses can occur 20 to 30 times or
more an hour.
The most common type is obstructive sleep apnea.
That means you are unable to get enough air through your mouth and nose
into your lungs. When that happens, the amount of oxygen in your blood
may drop. Normal breaths resume with a snort or choking sound. People
with sleep apnea often snore loudly. However, not everyone who snores
has sleep apnea.
When your sleep is interrupted throughout the
night, you can be drowsy during the day. People with sleep apnea are at
higher risk for car crashes, work-related accidents and other medical
problems. If you have it, it is important to get treatment.
Check
your Snore Score to see if you have sleep apnea
Sleep
apnea is a common disorder that can be serious. In sleep apnea, your
breathing stops or gets very shallow. Each pause in breathing typically
lasts 10 to 20 seconds or more. These pauses can occur 20 to 30 times or
more an hour.
(National
Heart, Lung, and Blood Institute)