October 20, 2019

New study explains the association to sleep disturbance and cognitive decline

Alzheimer’s disease and related disorders (ADRD) are a group of conditions that cause mild cognitive impairment (MCI) or dementia. These conditions affect one’s ability to function socially, personally, and professionally. It’s important to recognize that Alzheimer’s 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 on 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 having an increased the risk of cognitive problems. For example, individuals with sleep apnea have an increased risk for developing mild cognitive impairment (MCI) approximately 10 years earlier than healthy individuals.

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

After five or more nights of tracking their sleep, each participant came to the School of Medicine 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 has accumulate during that day.

The researcher team then compared each individual’s amyloid beta and tau levels after the disrupted night to the levels after the uninterrupted night and found a 10% increase in amyloid beta levels after a single night of interrupted sleep 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.

It is highly unlikely that there is an overall increased risk of developing ADRD simply from a single bad night or a week of poor sleep.  Amyloid beta and tau protein levels will go back down after the next good of sleep, however, the main issue is those that 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 to promote restful sleep. It is important limit use of screens at bedtime although it is very hard to today’s society. If necessary, I would recommend using apps like Night Shift (smartphones) and f.lux for laptops. In addition, it is important that people go to sleep around the same time every night. When the timing of your 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 keep you up and interfere with sleep. It is best to avoid these four to six hours before bedtime. Finally, try to get your workout in earlier in the day. Exercise increases cortisol and can make hard trying to fall asleep. If 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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