Brain disease may cause death during sleep
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When an elderly person dies in his or her sleep, cessation of breathing related to the loss of neurons in a particular area of the brain could be a possible cause of death, if animal experiments are any indication.
A brain region called the ventrolateral medulla is critical for generating regular, rhythmic breathing, and neurons in this area show high levels of a receptor termed NK1R. Dr. Leanne C. McKay and colleagues at the University of California Los Angeles theorized that a lack of NK1R-carrying neurons could underlie central sleep apnea.
Sleep apnea is a condition in which breathing stops for short, usually brief periods, during sleep. The most common form is obstructive sleep apnea, when airway passages collapse and block breathing, but it can also arise when respiration signals from the brain are interrupted—known as central sleep apnea.
To test their theory, the researchers studied rats after the animals were injected with a toxin that selectively kills off neurons carrying NK1R.
After 4 days, respiratory disturbances had increased from 4 to 66 episodes per hour during sleep, and the rate worsened even more over the next two days, the team reports in the research journal Nature Neuroscience.
From day 7 on, the animals developed a highly fragmented sleep pattern and reduced total sleep time. While awake, breathing became increasingly irregular.
By 10 days, the rats stopped breathing immediately upon falling asleep, starting again only after they awakened.
“Central sleep apnea becomes more prevalent as people get older,” McKay pointed out. “We suggest that these neurons are slowly deteriorating, and because (the elderly) heart and lungs are becoming weaker as well, they become more susceptible to respiratory failure during sleep.”
McKay said the situation may also arise in patients with disorders like Parkinson’s or Lou Gehrig disease. They are prone to have sleep disorders, “particularly central sleep apneas,” McKay told Reuters Health “However, these patients are so ill in many other respects that problems during sleep associated with breathing tend to be overlooked.”
SOURCE: Nature Neuroscience, online August 7, 2005.
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