Dream Catcher

The neuroscience of our night life

Can bad dreams foretell a dementing illness?

Bizarre and aggressive dreams can be an early sign of illness.

Sleep disorder may be one of the earliest signs of neurodegenerative disorder, including early Alzheimer's disease (AD). We know for example, that REM Behavior Disorder (RBD) may precede a dementing disorder by several years. RBD involves the acting out of dreams while still asleep. The dreamer may be utterly convinced that he and his bed partner are under attack from a violent intruder and thus the dreamer may kick, fight and literally run-off while still asleep. If you or someone you know is experiencing dreams like these it may be worth contacting a sleep specialist for a check-up to rule out a disease process.

We know that mild cognitive disorder often precedes a full blown dementing process for some years before onset of that dementing illness. If significant sleep disturbance could be accurately and easily identified in individuals with mild cognitive impairment (MCI) it may be possible to slow conversion to AD and other dementias by treating the sleep disorder. The most sensitive sign of sleep disorder may sometimes be dreams--or that is bizarre or disturbing dreams. 

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Clinically significant sleep (and possibly dream) disturbances are indeed present in 14% to 59% of persons with mild cognitive impairment (MCI) (Beaulieu-Bonneau and Hudon, 2009), depending on how sleep disturbance is measured. In addition, sleep disturbances in MCI appear to be significantly correlated with various types of cognitive impairment in the two major subtypes of MCI: amnestic (aMCI) and non-amnestic (naMCI) (Beaulieu-Bonneau and Hudon, 2009). Unfortunately, these data are based on only a handful of studies (N=20 studies), only three of which employed objective measures of sleep quality. None of these studies looked at dreams of MCI patients either.

The scarcity of studies on sleep and dreams in individuals with MCI is not surprising given the formidable logistical problems of recruiting adequate numbers of individuals with MCI subtypes and of objectively measuring sleep functions in these individuals. What is needed at this point is an adequately powered study of subjectively and objectively measured sleep and dream processes in the two major subtypes of MCI.

If we can extrapolate from what we know of dreams in individuals with RBD what can we expect concerning content of dreams in people with MCI? At a minimum we can expect elevated levels of aggression (both by and against the dreamer) relative to age-matched controls as well as greater amounts of bizarre imagery. Once again these ideas need to be tested and re-tested before they can be used to help predict risk for MCI or dementia.

Reference
Beaulieu-Bonneau S, Hudon C. Sleep disturbances in older adults with mild cognitive impairment. Int Psychogeriatr 2009 21(4):654-66.

Patrick McNamara, Ph.D., is Associate Professor of Neurology at Boston University School of Medicine and the author of numerous books and articles on the science of dreams.

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