Science Update

New study explores the association between sleep disturbance and cognitive decline


Alzheimers disease and related disorders (ADRD) are a group of conditions that cause mild cognitive impairment or dementia. These conditions affect ones ability to function socially personally and professionally. Its important to recognize that Alzheimers disease begins long before symptoms start just like many other conditions. There is evidence that simple prevention strategies can reduce the risk of ADRD by as much as 50%.

According to a new study published this past Monday in the journal Brain researchers demonstrate how sleep disruption increases amyloid beta and tau proteins which are associated with ADRD.

Previous studies have shown poor sleep increasing the risk of cognitive issues. For example individuals with sleep apnea have an increased risk for developing mild cognitive impairment approximately 10 years earlier than healthy individuals.

In this new study seventeen adults ages 35 to 65 with no sleep issues or cognitive impairment wore a sleep monitor for up to two weeks that tracked how much they slept each night.

After five or more nights of tracking their sleep at home each participant went on site to sleep and have their brain waves monitored. Half the participants randomly had their sleep disrupted. These individuals reported feeling tired and unrefreshed even though they slept just as long as usual and rarely recalled being awakened during the night. Each person had a spinal tap to measure the levels of amyloid beta and tau in the CSF fluid.

After a month or so this process was repeated except that those who had their sleep disrupted the first time slept undisturbed and those who had slept uninterrupted initially were disrupted when they began to enter deep slow-wave sleep. (This is the time when neurons rest and the brain clears away the molecular byproducts of mental activity that have accumulated during that day.)

The research team then compared each individuals amyloid beta and tau levels after the disrupted night to the levels after the uninterrupted night and after a single night of interrupted sleep found a 10% increase in amyloid beta levels but no increase in tau protein levels. However individuals whose sleep monitors showed they had slept poorly at home for the week prior to the spinal tap showed a spike in levels of tau levels. Amyloid levels normally change more quickly than tau so this was not surprising.

By no means is this saying there is an overall increased risk of developing ADRD simply from a single bad night or week of poor sleep.  Amyloid beta and tau protein levels will go back down after the next good night of sleep; however the main issue is regarding those who have chronic sleep issues. This can lead to chronically elevated amyloid levels leading to increased risk of ADRD.

It is important to address the environment in order to promote restful sleep. Limit the use of screens at bedtime although this is very difficult in todays society. If necessary I would recommend using apps like Night Shift (smartphones) and f.lux for laptops. In addition it is important to go to sleep around the same time every night. When the timing of sleep is shifted even if the duration of sleep is the same it's not going to be as restorative. Caffeine and other stimulants can interfere with sleep so it is best to avoid these four to six hours before bedtime. Finally workouts should be done earlier in the day as exercise increases cortisol and can make it more difficult to fall asleep. If working out earlier in the day is not possible consider phosphatidylserine post-workout.

By Michael Jurgelewicz DC DACBN DCBCN CNS

Source: David M. Holtzman et al. Slow wave sleep disruption increases cerebrospinal fluid amyloid-β levels. Brain July 2017 DOI: 10.1093/brain/awx148

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