Your brain is a glutton for oxygen.
Although it makes up only about 2% of your body weight, your brain uses about 20% of your oxygen supply. And while other organs can cope with low oxygen for a short time, your brain can’t. It has virtually no backup plan when oxygen levels drop. Within seconds, brain cells start to struggle. Within minutes, they start to die.
This is one very big reason why obstructive sleep apnea (OSA) is so dangerous.
Sleep apnea occurs when your airway becomes blocked during sleep. It can happen when muscles around the top of the throat relax or when the tongue falls back or when the jaw slides back. Each time it does, your body startles awake to get you breathing again – often so quickly, you don’t even realize it. Each episode temporarily reduces oxygen levels in your blood. Repeated cycles of this night after night create a pattern of oxygen deprivation that your brain just wasn’t designed to handle.
New research in the journal Neurology shows just how significant this impact can be.
Thirty-seven older adults with healthy brain function took part. Each underwent an overnight sleep study and received advanced brain imaging. Twenty-four of the participants had OSA.
The results showed that those with even mild sleep apnea experienced brain changes in areas that are crucial for forming memories – particularly when their oxygen levels dropped during REM sleep. About 20 to 25% of your total sleep time is spent in this stage, typically in longer periods toward morning. It’s a time when the brain is very active. It’s when things like dreaming and memory consolidation take place.
Here, low oxygen levels were found to be strongly linked to more white matter hyperintensities – small areas of damage to blood vessels in the brain. The changes were most prominent in the frontal and parietal lobes, both of which are highly active during REM sleep and especially susceptible to oxygen loss.
What’s more, that vascular damage was directly connected to thinning of a brain area called the entorhinal cortex. That’s often the first region of the brain affected by Alzheimer’s. Participants with thinner entorhinal cortices were found to have worse overnight memory retention, suggesting that sleep-related oxygen deprivation was actively interfering with the brain’s ability to process new memories.
What makes this all the more concerning is that this damage was happening in people who had no memory problems and whose sleep apnea would be considered “mild.”
This may help explain why many people with AHI scores that indicate only “mild” OSA may still complain of mental fogginess or memory issues. It also serves as a good reminder that while AHI can give us an idea of how often a person stops breathing as they sleep, it gives only a partial picture of what’s going on.
In this study, even people with relatively low AHI scores experienced significant oxygen drops that were linked with changes in the brain.
“We may have found a missing piece of the puzzle,” said study co-author Dr. Michael Yassa in a news release.
Low oxygen during REM sleep seems to harm tiny blood vessels in the brain, and that damage shows up in areas we rely on for memory. This might help explain why even mild sleep apnea can impact brain health long before memory problems show up.
While severe sleep apnea causes obvious symptoms such as loud snoring, gasping, and extreme daytime fatigue, mild OSA can fly under the radar for years. Many people may brush off their everyday tiredness, attributing it to stress or being over-busy, unaware that their brain’s memory systems may be under nightly assault.
This simple test can help you see if your daytime fatigue may be a problem – and whether a formal sleep test is in order. If it does turn out to be apnea, oral appliance therapy could mean a healthier cognitive future for you.