What Can a Sleep Study Diagnose? More Than Most People Realize

Nothing is worse than lying awake at 3am, wondering how many sheep you’ll have to count or breathing exercises you’ll have to complete before falling back to sleep. If this happens regularly, it’s easy to chalk it up to being a “bad sleeper,” but an underlying health condition could be to blame. A sleep study may help you determine if this is the case, but what, exactly, can a sleep study diagnose?

A sleep study evaluates various health metrics, such as heart rate or airflow, while someone sleeps. These studies can be done in a sleep clinic or from your own bed. If you’re tossing and turning, talking to a healthcare provider about sleep study options may be the next logical step. 

But just what can a sleep study diagnose? Turns out, a lot. Continue reading to learn about the different test types and how a sleep study can help you better understand your sleep health.

What does a sleep study measure?

What a sleep study measures varies from test to test. And yes, that’s a total cop-out answer, but it’s because different devices measure different aspects of sleep health.

Common metrics for a sleep evaluation include:

• Brain wave activity: Some sleep studies use EEG electrodes attached to the scalp to monitor brain activity while someone sleeps.

• Breathing: Airflow, oxygen saturation, and other markers of how someone is breathing can be measured in multiple ways, often with an electrode or other wearable device that sits over the mouth or on the chin. 

• Heart rate: A device around the chest, such as an electrocardiogram-based home sleep apnea test (HSAT), can measure someone’s heart rate and any variability in it while they are sleeping. 

• Muscle movement: Electrodes hooked up to muscles throughout the body can measure movement.

• Jaw movement:  It’s also common to have an electrode or other device near the jaw to measure if the jaw moves during the night.

• Snoring: Some studies use a special microphone to record snoring or other noises while someone sleeps. 

Most sleep studies fall into two-camps: at-home or in-lab. First up, we have at-home studies. Jamila Battle, MD, a triple board certified physician in sleep, family medicine, and addiction, explains that these tests measure metrics associated with breathing. They’re most commonly used in cases of suspected obstructive sleep apnea, though they may help test for other breathing disorders that occur at night too.

Meanwhile, an in-lab sleep study (called a polysomnography) helps assess a broader range of sleep disorders, says Dr. Battle. “In addition to breathing and oxygen levels, it measures brain waves, eye movements, muscle activity, heart rhythm, and leg movements,” she explains, “This allows sleep specialists to evaluate for a broader range of sleep disorders.”

What conditions can a sleep study diagnose?

So what exactly can a sleep test detect? Sleep studies show signs of sleep apnea, narcolepsy, restless leg syndrome, parasomnias, and sleep-related seizures.

Sleep apnea (obstructive and central)

Sleep apnea is a condition where breathing stops and starts throughout the night. It prevents the body from getting enough oxygen and disrupts restorative sleep. There are two types of sleep apnea — the National Heart, Lung, and Blood Institute explains the difference:

• Obstructive sleep apnea (OSA): When the upper airway is blocked throughout the night

• Central sleep apnea: When the brain does not signal to the respiratory system to breathe

Both can be detected by either an in-lab or at-home test, though differentiating the two may not be possible with at-home sleep tests, as only in-lab studies measure brain wave activity. 

Additionally, not all cases of sleep apnea can be caught in a sleep study that takes place in a single night. “One thing I wish more patients understood is that sleep apnea is not always the same every night,” says Dr. Battle, “Factors such as sleeping on your back, alcohol use, nasal congestion, medications, illness, weight changes, and the amount of REM sleep you get can all affect how severe sleep apnea is on a given night.”

Dr. Battle adds that this is also the reason why treatments, like CPAP therapy, should be used consistently, as healthcare providers cannot reliably predict the nights when sleep apnea may be worse or better. 

Narcolepsy

Narcolepsy is a neurological disorder where someone feels sleepy during the day, often accompanied by feeling too awake at night, according to the National Institute of Neurological Disorders and Strokes. It’s a rare condition, with a 2025 population study Sleep Medicine X estimating it affects 37.7 out of every 100,000 individuals.

And if this sounds similar to conditions like depression or burnout, it’s because this is a bit of symptom overlap. In fact, a 2023 review in the Journal of Psychiatry and Neuroscience flags that it’s incredibly common for narcolepsy to be misdiagnosed. 

That’s why it may be useful to see a sleep specialist for daytime sleepiness, even if you think it’s due to a low mood or tough period at work. They may order a sleep analysis, though Funke Afolabi-Brown, MD, FAASM, a triple board certified sleep medicine physician, notes that in order to diagnose narcolepsy, an in-lab nighttime sleep study must be paired with a daytime nap study as well. 

Restless legs syndrome and periodic limb movement disorder

If you’ve ever felt an uncontrollable urge to move your legs when sleeping (or had your partner report that you do this), it may be restless leg syndrome (RLS). According to a 2026 JAMA review, 3% of US adults experience RLS at least twice a week, and this condition increased the risk for heart disease, depression, and suicidal thoughts. 

And not to sound like a dictionary, but the word syndrome actually refers to a group of conditions or symptoms that co-occur, per the National Human Genome Research Institute. One of the most commonly occurring conditions under the restless leg umbrella is periodic limb movement disorder (PLMD). This is when a person’s lower body twitches when asleep, per the National Library of Medicine. Many types of RLS, including PLMD, may also be diagnosed with an in-lab sleep test.

Parasomnias

Sleeping walking, night terrors, and acting out dreams during REM sleep all fall into the parasomnia club. Parasomnias are a group of conditions that cause abnormal behavior when sleeping. 

Dr. Afolabi-Brown says that an in-lab sleep test plays a part in diagnosing these conditions, and they are important to diagnose. Untreated parasomnias lead to an injury risk when acting out dreams. Plus, there’s an association between certain types of  dementia and parasomnias, per a 2024 article in Continuum.

Sleep-related seizures

An in-lab sleep study may provide useful data for diagnosing some sleep-related seizures. Specifically, the EEG electrodes that monitor brave wave activity can provide important data on whether seizures occur while sleeping. 

One common cause of seizures when sleeping is sleep-related hypermotor epilepsy (SHE). Medline Plus reports that SHE is less common than other types of epilepsy. Though like any other type of epilepsy, prompt diagnosis and treatment can greatly improve someone’s quality of life.

What conditions can’t a sleep study diagnose?

A sleep study diagnosis is possible for many conditions, though not every sleep disturbance can be determined through these tests. They can’t, for example, diagnose insomnia or circadian rhythm disorders (problems with your body’s sleep awake cycle, per the National Heart, Lung, and Blood Institute). 

“A sleep study also cannot determine every possible reason someone feels tired, since fatigue can be influenced by medical conditions, medications, mental health, lifestyle factors, and sleep habits,” says Dr. Battle.

Home sleep test vs. in-lab sleep study: What's the difference?

Taking a sleep study at home is a reliable, accurate way to determine if you have sleep apnea. Meanwhile, an in-lab study assesses more symptoms. 

More, however, doesn’t always mean better. Both are reliable, and each has its own sleep study test procedure and set of pros and cons. Here’s a full run-down on the differences between a home sleep study vs. lab study.

In-lab polysomnography

• What it is: An overnight sleep apnea test delivered in a hospital, sleep lab, or clinic

• What it can diagnose: Sleep apnea, narcolepsy, restless leg syndrome, parasomnias, sleep-related seizures. The collected data may also help determine if there are certain underlying heart, lung, or neuromuscular diseases, though a sleep study alone can’t diagnose these conditions. 

• When it’s appropriate: “If there is concern for conditions such as central sleep apnea, hypoventilation, significant heart or lung disease, neuromuscular disease, severe insomnia, seizures during sleep, narcolepsy, or certain parasomnias, an in-laboratory sleep study is more appropriate,” advises Dr. Battle.

• Limitations: Staying overnight in a sleep lab can throw off your routine and means you have to find transport to and from the lab (and possibly childcare. Also, people often sleep very differently in strange environments compared to the comfort of their home, which can misrepresent a typical night of sleep. Centers that conduct these tests usually have a wait list and take longer to share results. 

Home sleep test

• What it is: A sleep test taken from the comfort of your bed, facilitated by a virtual sleep clinic.

• What it can diagnose: Sleep-disordered breathing conditions, most commonly sleep apnea.

• When it’s appropriate: A sleep study at home is appropriate when a sleep specialist suspects sleep apnea. These studies provide fast, accurate results and are delivered directly to your door, no waitlist or travel necessary.

• Limitations: An at-home test is a bit more limited, says Dr. Afolabi-Brown, because it can only diagnose breathing-related disorders. 

There’s also a lot of variation in home testing devices, meaning you may have to put on your detective cap and search for a device that’s as rigorous as an in-lab test. And the best indicator of a good at-home test? It’s FDA-cleared or FDA-approved. Both indicate the Food and Drug Administration (FDA) found the device to be safe and effective for its stated purpose.

Another major advantage of some at-home tests, including the one from Dreem Health, is that they take place over two nights. This leads to more data than a one night test, which may be vital when diagnosing a condition with fluctuating symptoms (I’m looking at you, sleep apnea).

Want sleep apnea testing from the comfort of your home? Book a virtual sleep consultation with Dreem Health.

What a sleep study diagnosis makes possible

There’s nothing worse than taking a medical test, only for the results to come back inconclusive. Fortunately, a sleep test isn’t like that. It either helps inform a diagnosis, which opens the door to treatment and an improved quality of life. Or it rules out some conditions, getting you closer to discovering what’s causing your restless nights.

“A sleep test is just one piece of the puzzle,” says Dr. Battle, “The results are most meaningful when combined with your symptoms, sleep habits, medical history, and overall health.”

Dr. Afolabi-Brown adds that a negative or normal result doesn’t mean something is not wrong. There are many sleep conditions that won’t be picked up by a sleep test. In these cases, the results point a sleep specialist toward other conditions, moving you one step closer to a diagnosis. 

The bottom line

If you’re tossing and turning all night, a sleep study may be part of your diagnostic journey. It can assess sleep metrics related to multiple conditions, such as sleep apnea, narcolepsy, restless leg syndrome, and parasomnias. Alternatively, it can rule out these conditions, bringing you closer to a diagnosis. 

Sleep studies can be done in-lab or at-home, though in-lab studies often mean joining a waitlist and having to sleep somewhere else. To get accurate results for sleep apnea from the comfort of your own home, consider an FDA-approved at-home test, such as the one from Dreem Health. Get started with one of our sleep medicine specialists to learn more.

Frequently asked questions (FAQs) 

Will a sleep study show anxiety?

While anxiety at night is a common cause of disrupted sleep, it will not show up in a sleep study. A sleep study, however, may eliminate other sleep conditions, such as sleep apnea or restless leg syndrome.

Can a sleep study detect heart problems?

While sleep tests are designed to detect sleep health conditions, some may provide useful data on heart rate variability while sleeping that may help diagnose some heart conditions. 

What if I can’t sleep during a sleep study?

It’s normal to feel nervous about whether you will be able to fall asleep during a sleep test. However, you don’t need to sleep for the entire time for an at-home sleep device or in-lab sleep devices to pick up enough diagnostic data. If you feel nervous about this, a sleep medicine specialist may be able to offer relaxation techniques or breathing exercises to help you fall asleep during the study.