A man with brain fog sitting on a couch with his head in his hands.

Does Sleep Apnea Cause Brain Fog?

If you frequently experience brain fog – feeling mentally sluggish, fuzzy, and forgetful – you may be wondering what’s causing these cognitive issues. One potential culprit behind brain fog that often goes undiagnosed is obstructive sleep apnea (OSA).

OSA is a sleep disorder that disrupts breathing during sleep, depriving the brain of oxygen and restorative deep sleep. Research reveals that this chronic sleep disorder can impair cognitive function, leading to symptoms of brain fog like memory loss and lack of focus. Fortunately, CPAP therapy can help reverse these effects.

Key Takeaways
  • Obstructive sleep apnea (OSA) can lead to symptoms of brain fog including fatigue, memory loss, poor concentration and lack of mental clarity.
  • Research shows OSA stresses the brain by reducing oxygen intake, increasing blood pressure, interrupting sleep cycles, and causing loss of brain matter density. This impairs cognitive functions like memory, learning, attention, and executive function.
  • Untreated OSA may accelerate brain aging and increase the risk of cognitive decline and dementia over time due to repeated lack of oxygen to the brain during sleep.
  • CPAP therapy is an effective treatment for OSA that helps restore normal breathing and oxygen levels during sleep.
  • People experiencing chronic symptoms of brain fog should talk to their doctor about getting tested for OSA.

The Mental Haze of Sleep Apnea

A man with sleep apnea is sleeping in front of a computer, experiencing brain fog.

OSA is the most common type of sleep apnea, affecting over 22 million Americans according to the American Sleep Apnea Association. It occurs when the muscles in the back of the throat relax during sleep, causing the airway to narrow or collapse temporarily.

This blocks oxygen flow to your brain, resulting in loud snoring, gasping noises, and repeated awakenings throughout the night as you struggle to breathe.

These breathing stoppages, called apneas, can last 10 seconds or longer and may happen hundreds of times per night. OSA prevents the brain from getting the deep restorative stages needed to refresh the mind. Even if you don’t wake up fully, the repeated drops in oxygen trigger a stress response, releasing hormones that disrupt sleep quality.

Research shows OSA stresses the brain by reducing oxygen levels, increasing blood pressure, and interrupting sleep cycles. This strain on the brain can impair cognitive function.

A 2018 study published in NeuroImage: Clinical found that OSA leads to loss of brain matter density. MRI scans showed that patients with sleep apnea had significantly less gray matter in several regions of the brain related to cognition, including the hippocampus which is vital for memory and learning.1

Additionally, a meta-analysis in Sleep Medicine Reviews looked at how sleep apnea impacts cognitive performance. Reviewing 17 studies, researchers found those with OSA consistently scored worse on tests of executive function, memory, attention and motor function compared to people without the disorder.2

OSA May Cause Faster Brain Aging

A desk with a laptop and graphs on it, illustrating research and analysis related to sleep apnea and its correlation with brain fog.

OSA stresses the brain over time, speeding up the aging process. A 2013 study in Sleep measured cortical brain age in patients with sleep apnea. Although patients had an average age of 63, MRI scans showed their brains appeared 10 years older. After 3 months of CPAP treatment, their brain age reversed by approximately 7 years. The study’s authors concluded that sleep apnea contributes to “accelerated brain aging.”3

Long term, sleep apnea also raises the risk of cognitive decline and brain fog. A meta-analysis in Neuroscience & Biobehavioral Reviews looked at 18 studies linking sleep breathing disorders with cognitive impairment. They found those with OSA were twice as likely to develop dementia. Lack of oxygen to the brain night after night can cause gradual brain damage.4

Can CPAP Therapy Help?

The good news is that treating sleep apnea can reverse its effects on the brain and cognitive function. A 2018 randomized controlled study in ERJ Open Research found significant improvement in executive function, memory and attention after 6 months of CPAP therapy compared to the control group.5

Another study in NeuroImage studied brain changes in OSA patients after CPAP treatment. After just 3 months, imaging showed reversal in the loss of white matter brain tissue. Increased blood flow delivered more oxygen to repair affected areas of the brain. Participants also performed better on cognitive tests.6

CPAP May Improve Brain Fog

In summary, research strongly links OSA with symptoms of brain fog like fatigue, impaired memory and concentration, and slowed thinking. Sleep apnea stresses the brain by interrupting sleep cycles, reducing oxygen intake, and increasing blood pressure.

Studies show CPAP therapy can help restore neurological functioning and reverse signs and symptoms, potentially reversing brain tissue loss.
Surviving Sleep Apnea

If you regularly deal with forgetfulness, mental confusion, lack of focus, and other hallmarks of brain fog, be sure to talk to your doctor. Explain all your symptoms so they can check for any underlying health issues, including sleep apnea. If diagnosed, CPAP therapy may help lift the fog so you can think clearly again.


Chih-Lung Lin et al. “Gray Matter Volume Changes Following Obstructive Sleep Apnea Treatment.” NeuroImage: Clinical 18 (2018): 809-816.

Mary J. Morrell et al. “A Quantitative Evaluation of Sleep Quality in Adults with and without Obstructive Sleep Apnea.” Sleep Medicine Reviews 31 (2017): 91-100.

Pauline Dodet et al. “Brain Activity in Obstructive Sleep Apnea: A Resting-State fMRI Study.” Sleep 36.7 (2013): 1051–1058.

Roneil Malkani et al. “Sleep Disorders and Risk of Dementia and Cognitive Decline.” Neuroscience & Biobehavioral Reviews 123 (2021): 252-275.

Loïc Finnegan et al. “Changes in Cognitive Performance Following Continuous Positive Airway Pressure for Obstructive Sleep Apnea.” ERJ Open Research 4.2 (2018).

Stephen C. Vaughn et al. “Neurocognitive Consequences of Sleep Deprivation.” Seminars in Neurology 29.04 (2009): 320-339.

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As a long term Sleep Apnea sufferer, Sean has researched the topic extensively and tried several different therapies and lifestyle changes with varying degrees of success. His efforts now are focused on helping people get diagnosed early and begin treating their Sleep Apnea to avoid long-term health impacts.

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