Dementia and Sleep Apnea

Left untreated, obstructive sleep apnea (OSA) can harm more than just your sleep. Decades of
research show that this sleep disorder puts sufferers at increased risk of accidents,
cardiovascular illness, metabolic disease, and early death [1]. And now, dementia has been
added to this ever-growing list.
Dementia happens when there is damage or loss of nerve cells in the brain. While the
underlying causes of this damage remain unknown, health conditions that have a direct effect
on the brain are often found to be contributing factors — one such contributing factor being poor
sleep.

Sleep Apnea and Brain Health
Sleep is essential for brain health. Changes in brain wave activity during sleep are necessary for
memory consolidation, rest, and regeneration. Sleep also induces metabolic changes that are
necessary for waste clearance in the brain.
The importance of sleep is particularly evident when you consider that a single night of poor
sleep causes problems with thinking, memory, and mood. A lifetime of sleepless nights, on the
other hand, can result in neurodegeneration [2].
Sleep apnea is a common cause of poor sleep. This sleep disorder causes breathing to
repeatedly stop and restart as you sleep — leading to fragmented sleep. Sleep apnea also
causes fluctuations in blood oxygen levels and cerebral blood flow, further contributing to
neurodegeneration [3].
Is There a Link Between Sleep Apnea and Dementia?
While there’s no doubt OSA causes unfavorable brain changes, does it actually put you at risk
of dementia?

Many studies have often found a strong link between sleep apnea, dementia, and other
neurocognitive disorders. A systematic review and meta-analysis by Canadian researchers, for
example, looked at 11 studies with over 1.3 million patients and found up to a two-fold greater
risk for some forms of dementia [4].

An even bigger review examined three decades of research on this subject. This review found
that the evidence was clearest for longitudinal studies, with some noting an 85% higher risk of
developing dementia as a result of OSA [5]. A study carried out in Taiwan had similar findings,
showing a 3.2 times greater risk of dementia in older women with sleep apnea over a period of 5
years [6].
How Sleep Apnea May Play a Role in Dementia
Dementia is the result of damage to or loss of neurons in the brain. One underlying mechanism
behind this damage is an accumulation of proteins that lead to beta-amyloid plaques and
neurofibrillary tangles.

Researchers suggest that disrupted sleep causes problems in the removal of waste proteins in
the brain, causing their accumulation [5, 7]. Waste clearance is two times faster during sleep
than wakefulness, showing how much sleep is necessary for the brain.

But the clearest answer so far comes from a recently published University of Queensland
mouse study [8]. The study in question found that fragmented sleep alone doesn’t lead to
pathological changes we associate with dementia. Instead, it was the low oxygen flow to the
brain that caused damage to neurons that is associated with dementia.

This makes sense considering that other health issues that affect oxygen levels in the brain are
also known risk factors for dementia. Examples are aging, cardiovascular disease, stroke, and
smoking.

References:
1. Sulican C. Thirty Years of CPAP. ResMedica clinical newsletter. Published 2011; (14).
https://document.resmed.com/en-au/documents/articles/clinical_newsletter/resmedica14.
pdf

2. Lewis LD. The interconnected causes and consequences of sleep in the brain. Science.
2021 Oct 29;374(6567):564-568. doi: 10.1126/science.abi8375. Epub 2021 Oct 28.
PMID: 34709917; PMCID: PMC8815779.

3. Rosenzweig I, Glasser M, Polsek D, Leschziner GD, Williams SC, Morrell MJ. Sleep
apnoea and the brain: a complex relationship. Lancet Respir Med. 2015
May;3(5):404-14. doi: 10.1016/S2213-2600(15)00090-9. Epub 2015 Apr 14. PMID:
25887982.

4. Guay-Gagnon M, Vat S, Forget MF, Tremblay-Gravel M, Ducharme S, Nguyen QD,
Desmarais P. Sleep apnea and the risk of dementia: A systematic review and
meta-analysis. J Sleep Res. 2022 Oct;31(5):e13589. doi: 10.1111/jsr.13589. Epub 2022
Apr 2. PMID: 35366021.
5. Bubu OM, Andrade AG, Umasabor-Bubu OQ, Hogan MM, Turner AD, de Leon MJ,
Ogedegbe G, Ayappa I, Jean-Louis G G, Jackson ML, Varga AW, Osorio RS.
Obstructive sleep apnea, cognition and Alzheimer's disease: A systematic review
integrating three decades of multidisciplinary research. Sleep Med Rev. 2020
Apr;50:101250. doi: 10.1016/j.smrv.2019.101250. Epub 2019 Dec 12. PMID: 31881487;
PMCID: PMC7593825.

6. Chang WP, Liu ME, Chang WC, Yang AC, Ku YC, Pai JT, Huang HL, Tsai SJ. Sleep
apnea and the risk of dementia: a population-based 5-year follow-up study in Taiwan.
PLoS One. 2013 Oct 24;8(10):e78655. doi: 10.1371/journal.pone.0078655. PMID:
24205289; PMCID: PMC3813483.

7. Mendelsohn AR, Larrick JW. Sleep facilitates clearance of metabolites from the brain:
glymphatic function in aging and neurodegenerative diseases. Rejuvenation Res. 2013
Dec;16(6):518-23. doi: 10.1089/rej.2013.1530. PMID: 24199995.

8. Qian L, Rawashdeh O, Kasas L, Milne MR, Garner N, Sankorrakul K, Marks N, Dean
MW, Kim PR, Sharma A, Bellingham MC, Coulson EJ. Cholinergic basal forebrain
degeneration due to sleep-disordered breathing exacerbates pathology in a mouse

model of Alzheimer's disease. Nat Commun. 2022 Nov 2;13(1):6543. doi:
10.1038/s41467-022-33624-y. PMID: 36323689; PMCID: PMC9630433.