For decades, sleep disturbance was a punch line: the cartoon dad snoring, the disgruntled partner burying their head under a pillow. But science is beginning to paint a less jovial picture. Sleep apnea—a relatively common disorder where breathing repeatedly stops and starts during sleep—is now being taken seriously as a potential biomarker for a host of major health conditions, from cardiovascular disease to Alzheimer’s, even anxiety and depression.
“Sleep is just as important for health as diet and exercise,” says Marishka Brown, director of the US National Center on Sleep Disorders Research. “Poor sleep affects both your mental and physical health; it contributes to cardiovascular disease, increases all-cause mortality, and raises risk factors like obesity, hypertension, and diabetes. And these impacts are independent—they’re not just knock-on effects from something else. Sleep is foundational.”
Obstructive Sleep Apnea (OSA) is one of the most common types of apnea, affecting an estimated 1 billion people worldwide. It occurs when the upper airway repeatedly collapses during sleep, interfering with breathing and lowering oxygen levels. The brain responds by jolting the sleeper awake—sometimes hundreds of times a night—before letting them drift off again, often unaware.
Sufferers may feel exhausted during the day and can experience memory problems. But more than this, the latest research suggests that sleep apnea may play an early and direct role in serious long-term illnesses, especially those affecting the brain.
“Traditionally, sleep apnea was thought of as a disorder that increases with age—especially in men—and leads to heart problems, maybe stroke,” says Bryce Mander, associate professor of psychiatry and human behavior at UC Irvine. “But over the last decade, it’s become clearer that it’s also a risk factor for neurological illnesses like Alzheimer’s and other neurodegenerative diseases.”
Each pause of breath triggered by apnea causes a drop in oxygen levels and a surge in adrenaline for the sleeper. “Over time, that raises the risk of high blood pressure, heart disease, and stroke,” says Atul Malhotra, a sleep medicine specialist and professor at UC San Diego. “There’s strong evidence now that sleep apnea is not just a marker of being unfit. Lean people get sleep apnea too,” he adds.
Hypoxemia—when oxygen levels in the blood are lower than normal—increases inflammation and oxidative stress on cells, explains Mander. “It’s associated with vascular pathology in the brain. So, your blood vessels become damaged, and that can damage the surrounding brain tissue,” he says.
This damage can accelerate the trajectory of a disease like Alzheimer’s or make the brain more vulnerable to it—and researchers now know the effects may appear years before outward symptoms.
A 2015 New York University study found that people with sleep-disordered breathing developed mild cognitive impairment, including Alzheimer’s, up to 10 years earlier than those without. However, those who received treatment for their sleep apnea had the same onset age as those without sleep-disordered breathing.
“Duration of untreated illness is one of the biggest predictors of long-term damage,” says Mander. “The longer you have OSA, the more havoc it can wreak on the body and the brain.”
Notably, the research showed that apnea can manifest differently in REM sleep: “A lot of the memory consolidation and emotional regulation … happens during REM,” Mander explains. “If you’re waking up during REM because of a breathing event, you're fragmenting that process. And if that’s happening night after night for years, it adds up.”
Early diagnosis, therefore, is critical—but it’s currently falling short. Diagnosis frequently relies on a partner noticing loud snoring, an unreliable signal at best.
“The reality is, women—and especially pregnant women—have been overlooked when it comes to sleep disorders,” says Brown. “Right now, our diagnostic standards for sleep apnea are based on a very narrow demographic—typically middle-aged men. But we know that women present differently.”
“What’s classified as ‘mild’ apnea in a man could be moderate or even severe in a woman, particularly during pregnancy,” she adds. “We’ve supported research in pregnant women that found even mild sleep-disordered breathing was an independent risk factor for maternal hypertension, preeclampsia, and gestational diabetes.”
Wearable tech companies are racing to fill the diagnostic gap. Samsung’s Galaxy Watch recently became the first wearable to receive De Novo authorization from the US Food and Drug Administration for detecting signs of OSA. But experts remain cautious. “Wearables and home sleep tests are improving, but they’re not yet a replacement for a full clinical diagnosis,” says Malhotra. “They can give a false sense of security—people see a score and think they’re fine when they’re not.”
Mander is also skeptical: “They’re not accurate enough to replace proper diagnosis,” he says. “They might be better than nothing—as long as you treat them as one piece of information, not the full picture.” While smartwatches and rings can track metrics like heart rate variability, they’re still not reliable at detecting breathing patterns, he adds.
The gold standard in diagnosis is polysomnography, a clinical sleep study that monitors brain waves, oxygen, heart rate, and muscle activity. But this is expensive and time-consuming, and doesn't scale well.
New home-based devices are now offering better options. Mander highlights WatchPAT, which uses finger, wrist, and chest sensors to detect apnea events by analyzing changes in blood vessels. There’s also ARES, a wearable headband monitor that measures airflow, oxygen levels, and sleep position, and NightOwl, a fingertip device that received FDA approval in recent years.
“It's a big step forward, especially for reaching underserved populations who might not be able to access a sleep lab,” Mander says. Still, there are limitations. “Right now, the home test doesn’t know if you’re awake or asleep, much less the sleep stage. It would probably miss people with REM-dominant OSA,” he says. “If we have devices that can detect when these events are happening—in REM versus non-REM—that could help us pick up people earlier and reduce their risk.”
Once diagnosed, CPAP—continuous positive airway pressure—remains the gold standard for treatment, despite being uncomfortable or claustrophobic for some users. It uses a small machine to deliver a steady stream of air through a mask, keeping the airway open during sleep. “CPAP improves symptoms, blood pressure, and we now have emerging evidence that it may reduce cardiovascular risk,” says Malhotra.
For those who can’t tolerate CPAP, new tools such as nasal inserts are emerging on the market. Some interventions are more unconventional—and yet surprisingly effective. “There’s an Australian study that showed learning the didgeridoo helped strengthen throat muscles and reduce OSA severity,” says Mander. “It’s a fun example, but it works.”
Ultimately, the most critical step is awareness. “We used to think snoring was just annoying or funny,” Malhotra says. “Now we understand that it can be a sign of a serious medical condition. If you snore heavily or feel constantly tired, don’t just brush it off—go see your doctor.”
