Can Sleep Apnea Kill You? What the Long-Term Studies Show

Someone told you that you stop breathing in your sleep, or a home test came back with a number you do not understand, and the question underneath everything is the one you typed: can this actually kill me?

The honest answer is yes, it can, and it is almost never the way people picture it. You are very unlikely to suffocate in the middle of one pause. The danger is slower and quieter than that, it is concentrated in one group of people, and it is one of the few serious risks in medicine that drops substantially once you treat the cause. This page goes through what the long-term studies actually found, by severity, so you can place yourself on the scale instead of guessing.

Quick Answer

Yes, but mainly when it is severe and untreated. In an 18-year study of 1,522 adults, people with severe sleep apnea had about three times the risk of dying from any cause compared with people without it, and those who were never treated had roughly five times the risk of dying from heart disease. Mild sleep apnea showed no measurable increase in death risk in the largest study. The killers are heart attack, stroke, sudden cardiac death during the night, and car crashes from daytime sleepiness, not choking during a single pause. Treatment that is actually used for most of the night is linked with a substantially lower risk.

In this guide:

• What Happens During an Apnea
• What the Long-Term Studies Found
• The Risk by Severity, Ranked
• The Heart: Where Most of the Risk Lives
• Dying in Your Sleep: The Night-Time Pattern
• Stroke
• The Risk Nobody Counts: Driving
• Does Treatment Lower the Risk?
• Who Is Most at Risk
• Check Yourself: The STOP-Bang Screen
• Signs It Needs Attention Now
• The Verdict

What Happens During an Apnea

In obstructive sleep apnea, the muscles that hold your throat open relax during sleep, and the airway narrows or closes. Air stops moving, or slows to a trickle, for ten seconds or more. The oxygen level in your blood starts to fall.

Then your brain notices, and it wakes you just enough to tighten those muscles again. Usually you do not remember it. You gasp or snort, breathing restarts, and you drift back down, and the cycle repeats. That is why a single pause is very unlikely to be what kills you: the body has a reliable alarm, and it goes off every time.

The harm comes from how often the alarm has to ring. Every event brings three things with it:

• A drop in blood oxygen, sometimes a deep one.
• A surge of adrenaline as the brain forces you awake, which spikes heart rate and blood pressure.
• A broken night. The arousals shred the deeper stages of sleep, which is where the daytime exhaustion comes from.

Doctors count these events per hour of sleep, and the result is called the apnea-hypopnea index, or AHI. Someone with severe apnea has 30 or more an hour, which can mean several hundred oxygen drops and adrenaline surges in one night, every night, for years. That repetition is the mechanism behind every risk on this page. It also explains why apnea wrecks the stage covered in how to get more deep sleep: you cannot stay in deep sleep while being woken 30 times an hour.

What the Long-Term Studies Found

Two large studies followed ordinary adults for years, measured their breathing during sleep at the start with proper sleep studies, and then counted who died. They are the best evidence there is on this question, and they agree on the shape of the answer.

The Wisconsin Sleep Cohort tested 1,522 adults and followed them for 18 years. After adjusting for age, sex, weight and other factors, people with severe sleep apnea had three times the risk of dying from any cause compared with people without it. When the researchers removed everyone who had been treated with CPAP, leaving only untreated severe apnea, the figure rose to 3.8 times. For death from heart disease specifically, it was 5.2 times. The result did not change when they accounted for daytime sleepiness, which matters: feeling fine during the day does not mean the risk is absent.

The Sleep Heart Health Study was bigger: 6,441 men and women aged 40 and over, followed for an average of 8.2 years, during which 1,047 of them died. Severe sleep apnea raised the risk of death from any cause by 46 percent. The increase was sharpest in men aged 40 to 70, where severe apnea roughly doubled the risk.

The same study also showed where the risk was not. Mild sleep apnea carried no measurable increase in death risk at all, and moderate apnea showed a small increase that did not reach statistical significance. That is the most useful single fact on this page if your test came back mild.

The Risk by Severity, Ranked

Your sleep study report will give you an AHI. This is what the evidence says about each band, from the Sleep Heart Health Study and the Wisconsin cohort.

The two studies give different sizes for the severe figure because they measured different people: Wisconsin started with younger working adults and looked specifically at untreated disease, while the Sleep Heart Health Study included older adults and did not separate out the treated ones. Both point the same way. Severe apnea raises the risk of death; mild does not appear to.

And these are the ways it actually kills, ranked by how strong the evidence is:

The Heart: Where Most of the Risk Lives

Several hundred adrenaline surges a night, each one pushing up heart rate and blood pressure, do not stay at night. Over years they are linked with high blood pressure that is hard to control, irregular heart rhythms such as atrial fibrillation, and damage to the heart and blood vessels.

The clearest study on the outcome that matters comes from Spain, where researchers followed men for about ten years in five groups: healthy men, simple snorers, men with untreated mild-to-moderate apnea, men with untreated severe apnea, and men with apnea being treated with CPAP. They counted fatal heart attacks and strokes.

Two things stand out. The untreated severe group died of heart attacks and strokes at more than three times the rate of healthy men, and after adjusting for other factors their risk of a fatal event was 2.87 times higher. And the men on CPAP had a rate almost identical to snorers and healthy men. This was an observational study, so the men who stuck with CPAP may have differed in other ways from those who did not, and it included only men. But it is the pattern that the rest of the evidence keeps repeating.

Dying in Your Sleep: The Night-Time Pattern

This is the part of the question people are really asking, and there is a striking piece of evidence behind it.

In the general population, sudden death from heart causes is most common between 6 a.m. and noon and least common between midnight and 6 a.m. Researchers at the Mayo Clinic looked at 112 people who had died suddenly from heart causes and had previously had a sleep study. In people with sleep apnea, 46 percent of those deaths happened between midnight and 6 a.m., compared with 21 percent in people without apnea and 16 percent in the general population. Apnea flipped the usual pattern. The more severe the apnea, the higher the night-time risk, and overall people with apnea had 2.57 times the risk of sudden cardiac death during those hours.

A later Mayo study followed 10,701 adults for up to 15 years. The strongest predictors of sudden cardiac death were how low oxygen fell during the night: a lowest overnight oxygen level below 78 percent was linked with 2.6 times the risk, and an average overnight oxygen below 93 percent with 2.9 times. An AHI above 20 raised the risk by 60 percent.

Keep the absolute numbers in view, though. In that group of more than 10,000 people, most of whom had been referred because a doctor suspected a sleep problem, the annual rate of sudden cardiac death was 0.27 percent, about one person in 370 per year. Apnea raises a small number, and it raises it most in people who are already older or have heart disease. If your sleep study report lists your lowest oxygen saturation, it is worth asking your doctor what it means for you.

Sleep apnea is not the only condition people worry about in this way; the same question comes up with reflux, and the answer there is quite different, as covered in can you die from acid reflux in your sleep.

Stroke

A study at Yale followed 1,022 patients referred for sleep testing, 68 percent of whom turned out to have sleep apnea. Over the following years, apnea roughly doubled the risk of having a stroke or dying from any cause, and after adjusting for age, weight, smoking, diabetes, cholesterol, atrial fibrillation and high blood pressure, the risk was still 1.97 times higher. The more severe the apnea at the start, the higher the risk.

The detail that matters here is that the link held even after accounting for blood pressure. It had long been assumed that apnea raised stroke risk only by raising blood pressure. This study suggested there is more to it than that, which is part of why the oxygen drops and arousals themselves are now treated as the problem, not just their effect on one number.

The Risk Nobody Counts: Driving

Most articles on this question talk only about the heart. For a younger person with sleep apnea, the more immediate danger may be the drive to work.

A night broken by arousals leaves the brain chronically short of sleep, and the result is micro-sleeps: lapses of a few seconds that the person often does not notice. A systematic review of the evidence concluded that people with untreated sleep apnea are clearly at higher risk of car crashes, with the increase likely to be somewhere between 1.2 and 4.9 times. Higher weight, a higher AHI and lower oxygen levels all predicted crashes.

This is also the risk that responds fastest to treatment. A second review, pooling nine studies of drivers before and after starting CPAP, found crash risk fell by about 72 percent. Daytime sleepiness improves after a single night of treatment, and performance in driving simulators improves within two to seven days.

If you have nodded off at the wheel, even once, or you have to fight to stay awake while driving, that is the most urgent reason on this page to get tested. It is also a risk you carry for other people, not just yourself.

Does Treatment Lower the Risk?

This is where most pages simply say “yes, use CPAP.” The real answer is more interesting, and it points at the thing that actually decides whether treatment protects you.

The disappointing trial. The SAVE trial, published in the New England Journal of Medicine in 2016, gave CPAP to people with moderate to severe apnea who already had heart disease or had had a stroke, and compared them with people who received usual care. After nearly four years, CPAP did not reduce heart attacks, strokes or cardiovascular deaths. It did reduce snoring and daytime sleepiness and improved mood and quality of life.

But look at how much the CPAP group actually used their machines: an average of 3.3 hours a night. Apnea is often worst in the later part of the night, during REM sleep, which is exactly the part a three-hour user is not covering.

The larger picture. A 2025 meta-analysis in The Lancet Respiratory Medicine pooled 30 studies covering more than 1.17 million people with sleep apnea. People on positive airway pressure therapy had a 37 percent lower risk of dying from any cause and a 55 percent lower risk of dying from heart disease, and the benefit grew with how much the therapy was used. Two things to weigh: most of those studies were observational, where people who use their machines faithfully may also look after their health in other ways, and the analysis was funded by a CPAP manufacturer. Even so, the direction is consistent with every other study on this page.

Put together, the lesson is not “CPAP works” or “CPAP does not work.” It is that treatment protects you in proportion to how much of the night it covers. A machine in the cupboard does nothing. If you cannot get on with CPAP, say so rather than quietly stopping: mask changes, pressure settings, oral appliances for milder cases, weight loss, positional therapy and implanted nerve stimulators are all options, and a sleep specialist can match one to your situation.

Who Is Most at Risk

Sleep apnea is far more common than most people assume. Estimates for the United States, based on the Wisconsin cohort and national weight data, put moderate to severe apnea at:

And most of those people do not know. An earlier Wisconsin study estimated that 82 percent of men and 93 percent of women with moderate to severe apnea had never been diagnosed, in a population with good access to healthcare. Women are more likely to be missed because their symptoms are more often fatigue, insomnia or morning headaches rather than the loud snoring that gets people sent for testing.

Risk is highest when severe apnea combines with other factors:

• Being a man between 40 and 70. This is where the Sleep Heart Health Study found the excess death risk concentrated.
• Existing heart disease, high blood pressure or atrial fibrillation.
• Alcohol, sleeping pills, or opioid painkillers at night. These relax the throat muscles further and blunt the brain’s wake-up alarm, which is the one safety mechanism that stops a pause from going on too long. This is a combination to raise with your doctor directly.
• Surgery under general anesthesia with undiagnosed apnea. If you have been diagnosed or suspect you have it, tell the surgical team before any operation. They will plan your anesthesia and recovery around it.

Check Yourself: The STOP-Bang Screen

STOP-Bang is an eight-question screen that anesthesiologists use before surgery to spot likely sleep apnea. Give yourself one point for each yes.

A score of 0 to 2 is generally read as low risk, 3 to 4 as intermediate, and 5 to 8 as high.

Here is how to read your score honestly. A 2022 meta-analysis in surgical patients found STOP-Bang catches about 88 percent of people with moderate to severe apnea, so it rarely misses them. But it also flags many people who turn out not to have it, so a high score is a reason to get tested, not a diagnosis. A low score is more reassuring: for severe apnea specifically, a negative result was correct about 93 percent of the time. If you scored 3 or more, or if anyone has watched you stop breathing whatever your score, ask your doctor about a sleep study. Many people can now do one at home.

Signs It Needs Attention Now

See a doctor soon, not at your next routine visit, if any of these apply:

• You have fallen asleep, or nearly, while driving. Stop driving long distances until this is assessed.
• Someone has watched you stop breathing for long stretches, or you wake up choking or gasping.
• Your blood pressure stays high despite medication.
• You have atrial fibrillation or heart failure and loud snoring. Apnea is common in both and makes them harder to control.
• You wake with headaches most mornings, or need to urinate several times a night without another explanation.
• You are exhausted after a full night in bed, for weeks. The sleep debt calculator can show whether you are simply short of sleep or getting the hours and still not recovering, which points towards a sleep disorder.

Call emergency services for chest pain, sudden weakness or numbness on one side, slurred speech, or fainting. Those are heart attack and stroke symptoms, and they need an ambulance, not a sleep study.

Key takeaways:

• Severe sleep apnea raised the risk of death about threefold over 18 years, and untreated, the risk of heart death about fivefold.
• Mild apnea showed no measurable increase in death risk in the largest study.
• The killers are heart attack, stroke, sudden cardiac death at night and car crashes, not suffocation during a pause.
• Treatment protects in proportion to use: 3.3 hours a night did not prevent heart events in a major trial.
• Most people with moderate to severe apnea have never been diagnosed.

The Verdict

Sleep apnea can kill you, and the evidence for that is solid. But it does it the slow way, through the heart, the brain’s blood supply and the steering wheel, not through one pause that never ends. The risk sits overwhelmingly with severe apnea that goes untreated, it is highest in men between 40 and 70 and in anyone with existing heart disease, and it is quietly common: most of the people carrying it have never been told.

That makes it one of the better problems to have found. It is easy to test for, often at home, and the treatments work when they are used for most of the night. If you scored 3 or more on STOP-Bang, if someone has watched you stop breathing, or if you have ever drifted off at the wheel, get a sleep study. If your result is mild and you feel well, the evidence says you can breathe a little easier.

And whatever the number turns out to be, a night without constant arousals is worth having for its own sake. What it does for the deepest stage of sleep, and what else protects it, is in how to get more deep sleep.