Sleep Disorders and Cognitive Decline: Large Study Analysis Confirms Important Link Between Sleep and Brain Health

We understand the importance of consistent quality sleep for health, but did you know research confirms that rest-disrupting disorders increase the risk of neurodegenerative diseases? A recent review of multiple studies found that people with sleep disorders face an increased risk of developing dementia. Keep reading for everything you need to know. 

Comprehensive study links sleep disorders to dementia

An April 2025 meta-analysis of 39 existing studies, published in the journal GeroScience, found that people living with obstructive sleep apnea—where breathing repeatedly stops and starts during sleep—had a 33 percent higher risk of developing all-cause dementia compared to those without it. 

Additionally, a 36 percent increased risk of dementia was indicated in participants with insomnia, which means a person is not sleeping well due to trouble getting enough sleep, not sleeping well or having trouble falling or staying asleep.

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Other sleep disorders, including excessive daytime sleepiness, restless leg syndrome and circadian rhythm issues, were also measured. People with these conditions exhibited a 33 percent increase in dementia risk. 

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The relationship between inadequate sleep and specific types of dementia was also analyzed. For example, obstructive sleep apnea was linked to a 45 percent higher risk of Alzheimer’s disease (the most common form of dementia). 

Insomnia was associated with a 49 percent increased risk of Alzheimer’s as well as a 59 percent higher risk of vascular dementia, which is the second most common variation and caused by a lack of blood flow to the brain. The other sleep disorders previously mentioned also presented a 97 percent increased chance of vascular dementia. 

As for general cognitive decline, obstructive sleep apnea was also associated with a 44 percent higher risk, while people with insomnia showed a 63 percent increased risk and other sleep disorders were linked to 55 percent high risk. 

What do the study findings mean about sleep and brain health?

All of the above figures are considered statistically significant, note study authors, stating that the findings provide “robust evidence for an association between a range of sleep disorders—including obstructive apnea, insomnia and other sleep disorders —and an elevated risk of dementia.” 

There are numerous mechanisms through which sleep impairments can cause brain damage, explain researchers. Insomnia, for instance, is associated with chronic activation of a neurological network that manages the body’s stress response, leading to elevated cortisol levels, systemic inflammation and chronic oxidative stress, all of which exacerbate brain degeneration, explain authors. 

Sleep deprivation further impairs the brain’s ability to clear out toxic proteins that are prominent in Alzheimer’s disease. And, disruption of circadian rhythms impairs the brain’s ability to restore itself, deregulates inflammatory pathways and disrupts the timing of critical metabolic and cognitive functions, note researchers. 

Experts weigh in on sleep disorders and cognitive decline

The amount and quality of sleep a person gets directly influences cognitive function, confirms Gunjan Narwani, MD, Houston Methodist Clear Lake Hospital and Houston Methodist Neurology Associates. 

“Chronic sleep deprivation—whether from poor sleep habits or an underlying sleep disorder—impairs attention, memory consolidation and decision-making,” she says. “Over time, this can contribute to cognitive decline.”

This is mainly because sleep plays a vital role in clearing toxins from the brain and supporting neuroplasticity, explains Dr. Narwani. Disrupted or insufficient sleep may accelerate age-related cognitive changes and has long been associated with an increased risk of developing neurodegenerative diseases. 

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“People often assume that forgetting things or feeling mentally sluggish is just part of getting older, but if sleep quality is poor, the brain isn’t getting what it needs to stay sharp,” adds Dan Caffrey, Certified Sleep Science Coach at Sleepopolis. 

Research shows that the link between fragmented sleep and increased risk of dementia is especially strong when oxygen levels drop, as they do in untreated apnea, he notes. 

“If someone regularly feels tired despite sleeping through the night, or experiences significant changes in memory or concentration, it’s important to talk with a physician,” advises Dr. Narwani. “Identifying and treating underlying sleep disorders early may help preserve long-term cognitive health.”