What Happens To Your Brain When You Have Undiagnosed Sleep Apnea

Sleep apnea affects an estimated 80 million adults in the U.S., yet it remains one of the country’s most underdiagnosed health conditions. Research suggests that up to four in five people with sleep apnea have no idea they’re living with it.

That blind spot comes at a cost — and not just to sleep.

Respiration-related sleep disorders like obstructive sleep apnea (OSA) are often dismissed as nighttime inconveniences: loud snoring, restless sleep, daytime fatigue. But sleep apnea is far more than a sleep problem. It’s a chronic neurological stressor, quietly reshaping how the brain functions night after night.

Studies suggest nearly 60 percent of people with OSA experience some degree of cognitive impairment, including difficulties with attention, working memory, and episodic memory. Mood disorders such as depression and anxiety are also more common. Over time, untreated sleep apnea has been linked to declines in concentration, executive function, and long-term memory.

So what’s actually happening inside the brain while someone with undiagnosed sleep apnea sleeps?

Sleep Apnea Isn’t Just A Sleep Disorder

“Obstructive sleep apnea is the repeated blocking of breathing occurring during sleep,” says Dr. Eric Kezirian, a professor of head and neck surgery at the David Geffen School of Medicine at UCLA.

When we’re awake, muscles in the throat stay active, keeping the airway open, Kezirian explains. During sleep, those muscles relax. In people with sleep apnea, that relaxation allows the airway to collapse, partially or completely blocking breathing — often dozens of times per hour.

Each blockage forces the brain to briefly wake the body just enough to restart breathing. These micro-awakenings usually go unnoticed, but they fragment sleep throughout the night. The result is non-restorative sleep, even if someone spends a full seven to nine hours in bed.

A Brain Stuck In Survival Mode

Sleep isn’t passive downtime for the brain. It’s an active period of repair, when memories are consolidated, neural connections are strengthened, and metabolic waste is cleared away.

With sleep apnea, that recovery process is repeatedly disrupted.

“Those with obstructive sleep apnea and the repeated blockage of breathing have awakenings from sleep that are also associated with release of catecholamines like adrenaline, preventing the body’s recovery and slowing down,” says Kezirian.

In other words, the brain spends the night in a low-grade fight-or-flight state. At the same time, repeated breathing interruptions reduce the amount of oxygen reaching the brain. Over months and years, this combination of fragmented sleep and intermittent oxygen deprivation takes a measurable toll on both brain structure and function.

Memory, Focus, And Executive Function Take The Hit First

Sleep apnea robs the brain of quality sleep, making next-day fatigue, irritability, and difficulty focusing almost inevitable. But beyond the yawns and short tempers, the consequences run deeper — and they’re far more serious.

Research shows that lower oxygen levels to the brain during REM sleep can damage white matter, the network of nerve fibers that allows different regions of the brain to communicate. If the white matter isn’t functioning as it should, your brain cells can’t send signals properly. When compromised, cognition suffers.

In a four-year study, neurobiologists at the University of California, Irvine found that people with OSA exhibited measurable white matter damage alongside declines in attention, visual memory and visual processing.

Even more concerning, chronic oxygen deprivation has been linked to vascular damage associated with thinning of the entorhinal cortex — an area of the brain critical for memory and one of the first regions affected in Alzheimer’s disease.

The Brain Can Bounce Back

If you have sleep apnea — or suspect you might — the good news is this: the brain is remarkably resilient.

Effective treatment doesn’t just improve sleep quality; it can also support brain health. Research shows that treating OSA with continuous positive airway pressure (CPAP) for as little as 12 months can reverse nearly all white matter damage. After one year of consistent treatment, study participants showed significant improvements in attention, memory, and executive function.

When To Take Symptoms Seriously

If you’re doing everything “right” yet still waking up foggy, unfocused, and drained, it may be time to look beyond the number of hours you’re sleeping and ask what’s happening during them.

A primary care physician or sleep specialist can assess symptoms and recommend a sleep study, either at home or in a lab. Even people classified as having “mild” sleep apnea on the Apnea-Hypopnea Index (AHI) Index can experience repeated drops in oxygen overnight — changes that may quietly affect brain health over time.

Sleep apnea isn’t always easy to spot, and its effects often build gradually. But addressing disrupted sleep sooner rather than later can help protect not just how rested you feel in the morning, but how your brain functions for years to come.

Presented by BDG Studios