January 12, 2009
People with a bizarre sleep disorder that causes them to kick, punch and cry out while dreaming are at dramatically increased risk of developing Alzheimer's or Parkinson's diseases, a new study reports.
Little is known about the disorder, called REM Sleep Behavior Disorder, but it is thought to mainly affect men in their 50s, 60s and 70s. It occurs when the brain activates the muscles during the REM, or rapid eye movement, stage of sleep. During REM sleep, the time when dreaming occurs, the eyes move rapidly and breathing continues, but muscles elsewhere in the body become frozen.
People with REM sleep behavior disorder, in contrast, act out and vocalize their dreams. It is different than night terrors, in which people have serious nightmares, or sleepwalking. It also differs from sleep apnea, a fairly common sleep ailment that causes the airways to collapse and people to temporarily stop breathing many times during the night. One recent study found that treating sleep apnea could help to ease the symptoms of Alzheimer's disease.
The new research suggests that the REM sleep disorder may be an early symptom of Alzheimer's, Parkinson's or other serious brain disease. The findings appeared in the medical journal Neurology.
Researchers at the Sleep Disorders Center at Sacre-Coeur Hospital in Montreal followed 93 people with REM sleep behavior disorder for 12 years. Most were men, with a mean age of 65. After five years, 14 had developed Parkinson's disease; 7 had Lewy body dementia, which shows symptoms of both Alzheimer's and Parkinson's disease; and 4 were diagnosed with Alzheimer's disease.
The researchers calculated that people with the sleep disorder are at more than 40 percent risk of developing a serious brain ailment within 10 years, and more than 50 percent after 12 years. In those without the disorder, the risk is less than 5 percent.
REM sleep behavior disorder may be related to degeneration in the brain stem, leading to symptoms like memory loss or tremors. Earlier studies suggested some relation between REM sleep problems and Alzheimer's, but the current study tracked patients for longer periods.
It is possible that REM sleep disorders may be among the earliest symptoms of Alzheimer's. The association between REM sleep behavior disorder and dementia had been observed before, but this study tracked it over a longer period than previous research.
R. B. Postuma M.D., J. F. Gagnon PhD, M. Vendette BSc, et al: "Quantifying the risk of neurodegenerative disease in idiopathic REM sleep behavior disorder." Neurology, December 24, 2008.