Sleep deprivation

Sleep problems linked to age-related cognitive problems

  • A very large Canadian study found that older adults with chronic insomnia performed significantly worse on cognitive tests.
  • A small study links older adults' increasing difficulties with consolidating memories to poorer synchronization of brainwaves during sleep.
  • A fruitful study shows that oxidative stress drives sleep, and that this is regulated by a specific molecule that monitors the degree of oxidative stress.

Chronic insomnia linked to memory problems

Data from 28,485 older Canadians (45+) found that those with chronic insomnia performed significantly worse on cognitive tests than those who had symptoms of insomnia without any noticable impact on their daytime functioning and those with normal sleep quality. The main type of memory affected was declarative memory (memory of concepts, events and facts).

Chronic insomnia is characterized by trouble falling asleep or staying asleep at least three nights a week for over three months with an impact on daytime functioning (mood, attention, and daytime concentration).

https://www.eurekalert.org/pub_releases/2019-05/cu-cia051519.php

Poor brainwave syncing behind older adults failure to consolidate memories

We know that memories are consolidated during sleep, and that for some reason this consolidation becomes more difficult with age. Now a new study shows why.

To consolidate memories (move them into long-term storage), low and speedy brain waves have to sync up at exactly the right moment during sleep. These brain rhythms synchronize perfectly in young adults, but in old age, it seems, slow waves during non-rapid eye movement (NREM) sleep are not so good at making timely contact with the speedy electrical bursts known as “spindles.”

These difficulties are thought to be due to atrophy of the gray matter in the medial frontal cortex.

The study compared the overnight memory of 20 healthy young adults to that of 32 healthy older adults (mostly in their 70s). Before going to sleep, participants learned and were then tested on 120 word sets. They were tested again in the morning. EEG results from their sleeping brains showed that in older people, the spindles consistently peaked early in the memory-consolidation cycle and missed syncing up with the slow waves.

http://www.futurity.org/memories-sleep-older-adults-1633432/

https://www.eurekalert.org/pub_releases/2017-12/uoc--obd121417.php

Oxidative stress governs sleep

A fruitfly study has shown how oxidative stress leads to sleep. Fruitflies (and, it is believed, humans) have sleep-control neurons that act like an on-off switch: if the neurons are electrically active, the fly is asleep; when they are silent, the fly is awake. The switch is triggered, it appears, by an electrical current that flows through two ion channels, and this, it now appears, is regulated by a small molecule called NADPH.

The state of NADPH reflects the degree of oxidative stress. Sleeplessness causes oxidative stress, driving the behavior of NADPH.

I'm wildly speculating here, but is it possible that increased sleep problems often found with age are linked to a growing inability of this molecule to sensitively monitor the degree of oxidative stress, perhaps due to high levels of oxidative stress??

https://www.eurekalert.org/pub_releases/2019-03/uoo-saa032119.php

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More studies linking poor sleep to Alzheimer's risk

  • Adults whose sleep quality declined in their 40s and 50s had more amyloid-beta in their brains later in life, while those reporting poorer sleep in their 50s and 60s had more tau tangles.
  • Greater tau protein was associated with less synchronized brainwaves during sleep.
  • Both amyloid-beta and tau levels increase dramatically after a single night of sleep deprivation, suggesting good sleep helps remove these proteins.
  • A large study found that older adults who consistently slept more than nine hours every night had twice the risk of developing dementia and Alzheimer’s disease within the next 10 years.
  • A large Japanese study found that those with sleep durations of less than 5 hours or more than 10 hours were more likely to develop dementia. However, those with short sleep could mitigate the effect with high physical activity.
  • A largish 12-year study found that poorer REM sleep was associated with an increased dementia risk.
  • Sleep apnea has been linked to higher levels of tau in the entorhinal cortex, poorer attention and memory, and slower processing speed.
  • Those with the APOE4 gene may be particularly vulnerable to the ill effects of sleep apnea.

Disrupted sleep in one's 50s, 60s raises Alzheimer's risk

A study involving 95 healthy older adults found that adults reporting a decline in sleep quality in their 40s and 50s had more amyloid-beta in their brains later in life, while those reporting poorer sleep in their 50s and 60s had more tau tangles. Those with high levels of tau protein were more likely to lack the synchronized brain waves during deep NREM sleep that are associated with a good night's sleep, and the more tau protein, the less synchronized these brain waves were.

Previous research has found that a dip in the amplitude of slow wave activity during deep NREM sleep was associated with higher amounts of beta-amyloid in the brain and memory impairment.

https://www.eurekalert.org/pub_releases/2019-06/uoc--dsi062619.php

Studies of healthy animals and humans have reported higher levels of amyloid beta after a single night of sleep deprivation, and that disruption of slow-wave sleep causes amyloid beta levels to rise as much as 30%. Moreover, a single night’s sleep deprivation has been found to increase tau levels by as much as 50% in cerebrospinal fluid.

These findings suggest that quality sleep helps the body clear excess amyloid and tau proteins.

https://www.eurekalert.org/pub_releases/2019-03/aps-spa032119.php

A preliminary study involving 20 healthy subjects aged 22 to 72 found beta-amyloid increases of about 5% after losing a night of sleep.

Many researchers believe the link between sleep disorders and Alzheimer's risk is "bidirectional," since elevated beta-amyloid may also lead to sleep disturbances.

https://www.eurekalert.org/pub_releases/2018-04/nioa-los041318.php

A very small study involving eight people aged 30-60, who experienced (over time) two or three different sleep situations, found that amyloid beta levels were 25-30% higher when individuals had a a sleepless night — putting those amyloid beta levels on par with the levels seen in people genetically predisposed to develop Alzheimer’s at a young age.

http://www.futurity.org/sleep-alzheimers-amyloid-beta-1642332/

A sleep study involving 17 healthy adults aged 35 to 65, found that those whose slow-wave sleep was disrupted (by a beeping sound that moved them into a shallower sleep) found a 10% increase in amyloid beta levels after a single night of interrupted sleep, but no corresponding increase in tau levels. However, participants whose activity monitors showed they had slept poorly at home for the week before showed a spike in levels of tau.

http://www.futurity.org/sleep-alzheimers-proteins-1485152-2/

https://www.theguardian.com/science/2017/jul/10/poor-sleep-increases-risk-of-alzheimers-research-reveals

Is too much sleep an early sign of dementia?

Data from 2,457 older adults (65+) in the Framingham study found that those who consistently slept more than nine hours every night had twice the risk of developing dementia and Alzheimer’s disease within the next 10 years, compared to those who slept less than nine hours a night.

Over the 10-year study period, 234 were diagnosed with dementia.

It’s suggested that one reason might be that those with depression tend to sleep longer. In any case, it’s thought that the longer sleep sessions reflect something else going on, rather than being a cause.

Education level also affected the degree of risk. Those without a high school degree who slept more than nine hours nightly had a 600% greater risk of later receiving a dementia diagnosis than people with a high school degree.

http://www.futurity.org/too-much-sleep-dementia-1439122/

Optimal sleep linked to lower dementia risk

A ten-year Japanese study involving 1,517 older adults (60+) found that dementia rates were higher in those with daily sleep duration of less than 5 hours or more than 10 hours, compared with those with daily sleep duration of 5-6.9 hours. However, those with short sleep duration who had high physical activity did not have a greater risk of dementia.

294 participants (19%) developed dementia in the 10 year period.

https://www.eurekalert.org/pub_releases/2018-06/w-osl060518.php

Lack of REM sleep linked to higher dementia risk

A study involving 321 older adults (60+; average age 67), who participated in a sleep study between 1995 and 1998, found poorer REM sleep was associated with an increased risk of developing dementia over 12 years.

During that period, 32 people were diagnosed with some form of dementia (24 with Alzheimer’s)

Those who developed dementia spent an average of 17% of their sleep time in REM sleep, compared with 20% for those who didn’t develop dementia. For every percent that REM sleep was reduced, there was a 9% increase in dementia risk, and an 8% increase in Alzheimer’s risk specifically.

No such associations were found for other stages of sleep, although that shouldn’t be taken to mean that other sleep stages don’t affect key features of Alzheimer’s.

http://www.futurity.org/rem-sleep-dementia-risk-1524842/

Sleep apnea linked to higher tau levels

A study involving 288 cognitively healthy older adults (65+) found that those who had sleep apneas had on average 4.5% higher levels of tau in the entorhinal cortex than those who did not have apneas, after controlling for several other factors that could affect levels of tau in the brain, such as age, sex, education, cardiovascular risk factors and other sleep complaints.

15% (43 participants) were reported by their bed partners as having sleep apneas.

This preliminary study was presented at the American Academy of Neurology's 71st Annual Meeting in Philadelphia, May 4-10, 2019.

https://www.eurekalert.org/pub_releases/2019-03/aaon-sam022619.php

Data from 1,752 older adults found that sleep-disordered breathing was associated with poorer attention and processing speed. In particular, increased overnight hypoxemia (oxygen saturation below 90%) was linked with poorer attention and memory, and more daytime sleepiness associated with poorer attention and memory and slower cognitive processing speed.

These associations were strongest in APOE-ε4 carriers.

https://www.eurekalert.org/pub_releases/2017-07/ats-sdm071817.php

Reference: 

[4468] Winer, J. R., Mander B. A., Helfrich R. F., Maass A., Harrison T. M., Baker S. L., et al.
(2019).  Sleep as a Potential Biomarker of Tau and β-Amyloid Burden in the Human Brain.
Journal of Neuroscience. 39(32), 6315 - 6324.

[4469] Ning, S., & Jorfi M.
(2019).  Beyond the sleep-amyloid interactions in Alzheimer’s disease pathogenesis.
Journal of Neurophysiology. 122(1), 1 - 4.

[4413] Shokri-Kojori, E., Wang G-J., Wiers C. E., Demiral S. B., Guo M., Kim S. Won, et al.
(2018).  β-Amyloid accumulation in the human brain after one night of sleep deprivation.
Proceedings of the National Academy of Sciences. 115(17), 4483 - 4488.

[4470] Lucey, B. P., Hicks T. J., McLeland J. S., Toedebusch C. D., Boyd J., Elbert D. L., et al.
(2018).  Effect of sleep on overnight cerebrospinal fluid amyloid β kinetics.
Annals of Neurology. 83(1), 197 - 204.

[4471] Ju, Y-E. S., Ooms S. J., Sutphen C., Macauley S. L., Zangrilli M. A., Jerome G., et al.
(2017).  Slow wave sleep disruption increases cerebrospinal fluid amyloid-β levels.
Brain. 140(8), 2104 - 2111.

[4438] Westwood, A. J., Beiser A., Jain N., Himali J. J., DeCarli C., Auerbach S. H., et al.
(2017).  Prolonged sleep duration as a marker of early neurodegeneration predicting incident dementia.
Neurology. 88(12), 1172.

[4473] Ohara, T., Honda T., Hata J., Yoshida D., Mukai N., Hirakawa Y., et al.
(2018).  Association Between Daily Sleep Duration and Risk of Dementia and Mortality in a Japanese Community.
Journal of the American Geriatrics Society. 66(10), 1911 - 1918.

[4474] Pase, M. P., Himali J. J., Grima N. A., Beiser A. S., Satizabal C. L., Aparicio H. J., et al.
(2017).  Sleep architecture and the risk of incident dementia in the community.
Neurology. 89(12), 1244.

[4472] Johnson, D. A., Lane J., Wang R., Reid M., Djonlagic I., Fitzpatrick A. L., et al.
(2017).  Greater Cognitive Deficits with Sleep-disordered Breathing among Individuals with Genetic Susceptibility to Alzheimer Disease. The Multi-Ethnic Study of Atherosclerosis.
Annals of the American Thoracic Society. 14(11), 1697 - 1705.

 

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Sleep apnea linked to problems recalling specific autobiographical details

  • The connection between sleep apnea and depression may lie in a problem with autobiographical memory.

Obstructive sleep apnea (OSA) occurs when a person's breathing is interrupted during sleep.

People with OSA are known to suffer memory problems and also have higher rates of depression.

A new study connects the two by finding that people with untreated OSA had problems recalling specific details about their lives. Previous research has established that persistent depression is associated with overly general autobiographical memories, where people don't remember many specific details of life events.

It may be that sleep apnea impairs the ability to either encode or consolidate certain types of life memories.

The study, involvidng 44 adults with untreated OSA and 44 healthy age-matched controls (average age 49), found that those with OSA had significantly more overgeneral memories: 52.3% compared with 18.9% of the controls.

OSA participants also had significantly poorer semantic recall of early adult life (facts from your personal history, like the names of your school teachers).

Across both groups, being older was associated with having a higher number of overgeneral autobiographical memories while higher depression was linked to having worse semantic memory.

https://www.eurekalert.org/pub_releases/2019-01/ru-sac013119.php

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Poor sleep in older adults may increase Alzheimer’s risk

  • Older people who spend less time in slow-wave sleep (deep sleep) have higher levels of the Alzheimer’s brain protein tau.

Poor sleep has been associated with Alzheimer's disease risk, but a new study suggests a specific aspect of sleep is important.

The study, involving 119 older adults (60+), of whom 80% were cognitively normal and the remainder very mildly impaired, found that decreased slow-wave sleep coincided with higher levels of tau in the brain and a higher tau-to-amyloid ratio in the cerebrospinal fluid.

Amyloid plaques and tau tangles develop for decades before cognitive symptoms of dementia emerge. Identifying the process at an early stage offers a possible window of opportunity for successful intervention.

Participants’ sleep at home was monitored over the course of a normal week, and participants also kept sleep logs of nighttime sleep and daytime napping. Thirty-eight people underwent PET brain scans for amyloid-beta and tau proteins, and 104 people underwent spinal taps to provide cerebrospinal fluid. Twenty-seven did both.

Those with increased tau pathology actually slept more, during both night and day, but their quality of sleep was poorer. In fact, daytime napping alone was significantly associated with high levels of tau, making it a useful indicator of risk.

https://www.futurity.org/alzheimers-disease-sleep-1954732/

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Being short of sleep may harm brain development

  • Brain scans of children with sleep apnea have found extensive reductions in gray matter.
  • Recordings of brain activity show that children's brains respond to sleep deprivation differently than adults’ brains do, and that this is linked to myelination of nerves in a specific area.
  • Sleep assessment from birth to age 7 has found that children getting less than the recommended levels of sleep at age 3 and after, were more likely to have cognitive and behavioral problems at age 7.

Untreated sleep apnea in children shrinks brain & may slow development

Brain scans of children who have moderate or severe obstructive sleep apnea have found significant reductions of gray matter across the brain.

The study compared brain scans from 16 children (aged 7-11) with obstructive sleep apnea to those from nine healthy children of the same age, gender, ethnicity and weight, who did not have apnea. The scans were also compared to 191 MRI scans of children who were part of an existing database.

The brains of those children with OSA showed reduced gray matter in multiple brain regions, including the frontal, prefrontal, and parietal cortices, temporal lobe, and the brainstem.

Sleep apnea is known to affect cognition in adults, but it may be that it is even more damaging in brains that are still developing. However, adult studies have also shown that treating sleep apnea reverses gray matter loss and improves cognition. This finding therefore emphasizes the importance of treating children's sleep apnea.

Sleep apnea affects up to 5% of all children (and we can only assume that this will get more common, if childhood obesity continues to rise).

Developing brain regions in children are hardest hit by sleep deprivation

Another study of sleep deprivation in children gives weight to the idea that it is particularly important for proper brain development that children get good sleep.

The study measured the brain activity in 13 healthy five to 12-year-olds as they slept. On the first occasion, the children went to bed at their normal bedtime; the second time, they stayed awake until late and thus received exactly half the normal amount of sleep.

The results indicate that children's brains respond to sleep deprivation differently than adults’ brains do. In adults, being deprived of sleep creates a greater need for deep sleep, which is manifested in greater slow-wave activation in the prefrontal cortex. In the children's brains, this slow-wave increase occurred in the back regions of the brain, in the parietal and occipital lobes. This suggests that these areas might be especially vulnerable to sleep deprivation.

Moreover, this difference was linked to levels of myelin in part of the visual system. Myelin increases as the brain matures. Those with higher levels of myelin in certain nerve fibers in the visual system displayed slow-wave activation that was more similar to that of adults.

The researchers conclude that adequate sleep is important for neuronal connections to develop properly.

Poor sleep in early childhood may lead to cognitive, behavioral problems in later years

A study involving 1,046 children whose sleep was assessed at various points in their first seven years has found that children who didn’t get enough sleep in their preschool and early school years were more likely to have problems with attention, emotional control and peer relationships at age seven.

Sleep was assessed through interviews with the mothers when their children were around 6 months, 3 years and 7 years old, and from questionnaires completed when the children were ages 1, 2, 4, 5 and 6. Mothers and teachers filled out questionnaires evaluating each child's executive function and behavioral issues at around 7.

Children living in homes with lower household incomes and whose mothers had lower education levels were more likely to sleep less than nine hours at ages 5 to 7. Other factors associated with insufficient sleep include more television viewing, a higher body mass index, and being African American.

Insufficient sleep was defined as being less than the recommended amount of sleep at specific age categories:

  • 12 hours or longer at ages 6 months to 2 years
  • 11 hours or longer at ages 3 to 4 years
  • 10 hours or longer at 5 to 7 years.

https://www.eurekalert.org/pub_releases/2017-03/uocm-usa031517.php

https://www.eurekalert.org/pub_releases/2016-10/uoz-dbr100416.php

https://www.eurekalert.org/pub_releases/2016-11/f-hkb112816.php

https://www.eurekalert.org/pub_releases/2017-03/mgh-psi030917.php

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