Why Sleep is So Important for the Brain

There are many insults to the body that contribute to the development of chronic disease.  Although diet/nutrition may be the most universally appreciated, it still remains poorly managed for many reasons.  In contrast, ongoing stress and poor/insufficient sleep are the most underappreciated.

 

sleep-diabetes

 

A recent CDC study found that one in three in the U.S. do not get the minimum required sleep required to reduce chronic disease risk.  Extensive study has demonstrated that at about 17-hours of sustained wakefulness all measures of performance in adults decrease equivalent to that which occurs at the standard blood alcohol level used to define drunk driving.  What prevents and repairs this decline is at least 7 hours of properly timed deep sleep.

Less than 7 hours of good sleep has been correlated with important increased risks of developing some of the most common chronic diseases including obesity, diabetes, high blood pressure, heart disease, stroke, and several mental disorders.

A recent study demonstrated a sharp rise in risk associated with poor sleep.  The highest rates of poor sleep clustered in the southeastern region of the United States and the Appalachian Mountains. Previous studies have shown that these regions also have the highest prevalence of obesity, diabetes and other chronic conditions.  More recently degenerative brain disease has been added to this list of chronic diseases associated with poor sleep.

Considerable research has examined why there is a relationship between poor sleep and poor brain function.  The results are sobering.  Poor sleep is an emerging risk factor for cognitive decline and structural brain changes typically seen in degenerative brain diseases such as Alzheimer’s and dementia.

 
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Brain scans called florbetapir-PET scans that show the degree of deposition of beta amyloid have been compared in otherwise matched groups of adults with good sleep and those with poor sleep.  Beta Amyloid is the protein that deposits in the brain causing the brain degeneration in Alzheimer’s disease.  Subjects with poor scores on sleep scales that measure both sleep duration and quality show significantly higher amounts of beta amyloid deposition as shown above as the yellow and orange areas in the front of the brain where the disease begins.

The build-up of beta amyloid in the brain associated with poor sleep is the result of poor brain “detoxification”.  Throughout the body the vascular circulation delivers nutrients to our tissues while the lymphatic system has the primary responsibility of removing the waste products.  The brain had always been unique in that it was thought to lack a lymphatic waste clearance system.  Some exciting new research, however, has defined a different type of lymphatic drainage in the brain called the “glymphatic drainage system”.

This fascinating video looks at the function of this brain waste drainage system.  The link to brain degeneration is that one of the waste products that this system must regularly remove from the brain is beta amyloid.  The brain makes some of this on a regular basis to do its “housekeeping” of old synapses (connections between brain cells).  The glymphatic system that should remove this each night preventing build-up only functions during good quality, adequate sleep.

The problem with the build-up of beta amyloid in the brain is that this protein slowly damages brain cells and disrupts their connections to other cells which are needed for memory.

 

sleep-alzheimers-progression

 

Multiple studies have looked at the effect of poor sleep on brain volume which is a standard testing method to document brain loss in Alzheimer’s disease.  They have all found associations between poor sleep and actual loss of brain volume a likely result of the increased beta amyloid deposition.  Additional study has taken the evaluation further to include cognitive testing.  As expected correlating with the imaging findings, poor sleep is associated with decline in cognitive function.

Researchers have shown great concern about the high rates of poor sleep in society coinciding with other factors such as aging of the population that are contributing to the rapidly increasing rates of degenerative brain disease.  The bright note, however, is that unlike aging, poor sleep is a modifiable risk factor.  Targeting adequate, good quality sleep is an important, modifiable factor in the treatment of brain disease.

Brager et al.  Relationships between sleep quality and brain volume, metabolism, and amyloid deposition in late adulthood. Neurobiology of Aging, 2016;41:107-114.

Lo et al.  SLEEP DURATION AND AGE-RELATED CHANGES IN BRAIN STRUCTURE AND COGNITIVE PERFORMANCE.  Sleep, 2014;37:1171-1178.

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