tau

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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Brain changes linked with Alzheimer's years before symptoms appear

  • A long-running study found subtle cognitive deficits evident 11-15 years before clear impairment, as were changes in tau protein.

A very long-running study involving 290 people at risk of Alzheimer's has found that, in those 81 people who developed MCI or dementia, subtle changes in cognitive test scores were evident 11 to 15 years before the onset of clear cognitive impairment. They also showed increases in the rate of change of tau protein in cerebrospinal fluid an average of 34.4 years (for t-tau, or total Tau) and 13 years (for a modified version called p-tau) before the beginning of cognitive impairment.

https://www.eurekalert.org/pub_releases/2019-05/jhm-bcl051419.php

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Gender differences in Alzheimer's disease may be linked to tau spread

  • Brain scans suggest that tau proteins may spread more rapidly through women’s brains, increasing Alzheimer's risk and speeding its progression.

Accumulating evidence suggests that tau spreads through brain tissue like an infection, traveling from neuron to neuron and turning other proteins into abnormal tangles, subsequently killing brain cells.

A new study using brain scans of healthy individuals and patients with MCI has found that the architecture of tau networks is different in men and women, with women having a larger number of regions that connect various communities in the brain. This difference may allow tau to spread more easily between regions, boosting the speed at which it accumulates and putting women at greater risk for developing Alzheimer's disease.

https://www.eurekalert.org/pub_releases/2019-07/vumc-rap071619.php

https://www.theguardian.com/society/2019/jul/16/research-why-alzheimers-more-likely-women-than-men-tau-protein

Gender & APOE status affects tau accumulation

A study involving 131 cognitively healthy older adults (mean age 77) and 97 with MCI, found that women with MCI who were ApoE ε4 carriers were more susceptible than men to tau accumulation in the brain. However, no gender differences were found among the cognitively healthy adults.

https://www.eurekalert.org/pub_releases/2019-06/sonm-ads062419.php

Reference: 

The findings of the first study were presented at the Alzheimer's Association International Conference July 14-18, 2019, in Los Angeles.

The second study was presented by Manish Paranjpe at the 2019 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI), Abstract 253: "Sex Modulates the ApoE ε4 Effect on Tau 18F-AV-1451 PET Imaging in Individuals with Normal Aging and Mild Cognitive Impairment," Manish Paranjpe, Min Liu, Ishan Paranjpe, Rongfu Wang, Tammie Benzinger and Yun Zhou.

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