August 8, 2005

‘Dying in sleep’ linked to sleep apnea – study

WASHINGTON (Reuters) - People who die in their sleep may
stop breathing because they have lost too many brain cells,
U.S. researchers reported on Monday.

Sleep apnea -- a condition in which people stop breathing
for long stretches of time in their sleep -- may sometimes be
caused by the destruction of cells in the brain stem, where
autonomic functions such as breathing are controlled, they

Tests on rats showed that the loss of key brain stem cells
that die off with age caused such disrupted sleep that the
animals eventually stopped breathing completely.

The same thing may be happening in elderly people, said
neurobiologist Jack Feldman of the University of California Los

"We wanted to reveal the mechanism behind central sleep
apnea, which most commonly affects people after age 65,"
Feldman said in a statement.

"Unlike obstructive sleep apnea, in which a person stops
breathing when their airway collapses, central sleep apnea is
triggered by something going awry in the brain's breathing

Writing in this week's issue of Nature Neuroscience,
Feldman and colleagues said they deliberately killed brain
cells in the pre-Boetzinger complex of the brains of rats -- a
region believed to be the "command post" for breathing in

Then they monitored the rats' breathing.

"We were surprised to see that breathing completely stopped
when the rat entered REM (rapid eye movement) sleep, forcing
the rat to wake up in order to start breathing again," said
Leanne McKay, who worked on the study.

"Over time, the breathing lapses increased in severity,
spreading into non-REM sleep and eventually occurring when the
rats were awake, as well."

Feldman believes the same thing could be happening in
elderly people, especially those with degenerative diseases
such as Parkinson's, which are marked by disturbed sleep.

"Our research suggests that the pre-Boetzinger complex
contains a fixed number of neurons that we lose as we age,"
Feldman said.

"We speculate that our brains can compensate for up to a 60
percent loss of pre-Boetzinger cells, but the cumulative
deficit of these brain cells eventually disrupts our breathing
during sleep. There's no biological reason for the body to
maintain these cells beyond the average lifespan, and so they
do not replenish as we age," said Feldman.

"As we lose them, we grow more prone to central sleep

And weaker people may not be able to rouse themselves when
this happens. They simply stop breathing.