Dementia is a syndrome characterized by a deterioration in cognitive function that results in behavioral problems and difficulty performing the activities of daily living. Alzheimer Disease is the common form of dementia in the elderly, accounting for about 60-80% of cases.  Under the microscope, the brains of people with Alzheimer Disease have abnormal clusters of protein fragments called amyloid plaques between nerve cells. The brain cells also contain aggregations of abnormal proteins called neurofibrillary tangles.  A new imaging technique called Amyloid PET tracing can measure how much amyloid plaque is present in the brain, but is currently used only for research purposes rather than being clinically available.  Thus, doctors now diagnose Alzheimer Disease based on a person’s presentation in the clinic and by ruling out other causes of impaired cognition such as Vitamin B12 deficiency, depression, and a low thyroid level.

A new study published in Science discovered that in mice, the brain’s system for flushing out toxic waste products is especially active at night.   The study author and University of Rochester neurosurgeon Maiken Nedergaard stated that “sleep puts the brain in another state where we clean out all the byproducts of activity during the daytime.”  These byproducts include the amyloid proteins that make up the plaques found in Alzheimer Disease.  Nedergaard explained that “brain cells shrink when we sleep, allowing fluid to enter and flush out the brain.  It’s like opening and closing a faucet.”  The study found that the harmful beta-amyloid protein clears out of the brain twice as fast in a sleeping rodent than in an awake and active one.

Besides providing insight into the mystery of why we need sleep, this interesting study may be a helpful contribution in the quest to someday prevent and effectively treat Alzheimer Disease.  Here is a Washington Post article describing the study published in Science.