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Common Sleep Problem Linked With Memory Loss
By Tara Parker-Pope


The part of the brain that stores memory appears to shrink in people
with sleep apnea, adding further evidence that the sleep and breathing
disorder is a serious health threat.

The findings, from brain scan studies conducted by researchers at the
University of California, Los Angeles, show for the first time that
sleep apnea is associated with tissue loss in brain regions that store
memory. And while the thinking and focus problems of sleep apnea
patients often are attributed to sleep deprivation, the scans show
something far more insidious is occurring.

“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, professor of neurobiology
at the David Geffen School of Medicine at U.C.L.A. The data appear in
the June 27 issue of the journal Neuroscience Letters.

Sleep apnea occurs when the muscles in the throat, soft palate and
tongue relax during sleep. They sag and narrow the airway and the
tongue slides to the back of the mouth, blocking the windpipe and
cutting off oxygen to the lungs. The sleeper gasps for air, wakes up
briefly and falls back to sleep in a cycle that repeats itself
hundreds of times per night. The result is loud snoring and chronic
daytime fatigue. The disorder also is linked to a higher risk of
stroke, heart disease and diabetes. An estimated 20 million Americans
have sleep apnea.

The study focused on structures on the underside of the brain called
mammillary bodies, so named because they resemble small breasts. The
researchers used magnetic resonance imaging to scan the brains of 43
sleep apnea patients. Compared to images of 66 control subjects, the
brains of the sleep apnea patients had mammillary bodies that were
nearly 20 percent smaller, particularly on the left side.

The structures also are known to shrink in patients who have other
forms of memory loss related to alcoholism or Alzheimer’s disease.

The researchers don’t know why the sleep disorder affects brain tissue
but theorize that it’s related to repeated drops in oxygen. During an
apnea episode, the brain’s blood vessels constrict, starving its
tissue of oxygen and causing cells to die. The inflammatory process,
also linked with heart disease and stroke, further damages the tissue.

“The reduced size of the mammillary bodies suggests that they’ve
suffered a harmful event resulting in sizable cell loss,” Dr. Harper
said. “The fact that patients’ memory problems continue despite
treatment for their sleep disorder implies a long-lasting brain
injury.”

The data show the importance of early diagnosis and treatment of sleep
apnea. Unfortunately, the most effective treatment is a continuous
positive airway pressure, or CPAP, machine that many patients find
unwieldy and uncomfortable. In a future study, the U.C.L.A.
researchers will explore whether vitamin B1 supplements might help
restore memory in sleep apnea patients by moving glucose into cells
and preventing cell death.