What Happens in a Sleep Study?

Science, Sleep, Sleep Apnea, Solutions

What Happens in a Sleep Study?

If you snore and are worried about sleep apnea, to get a diagnosis you’ll need to undergo polysomnography in a sleep study.

At SnoreLab, we often get asked “Can the app detect sleep apnea?” Some users have found tell-tale signs of sleep apnea in their SnoreLab recordings, but importantly, these don’t reliably tell you that you have sleep apnea. The only way to robustly diagnose sleep apnea is with a sleep study.

Some estimates put the rate of sleep apnea amongst people aged 30-60 at 16.5%, but the vast majority of these people are undiagnosed [1]. This is because there is a lot of anxiety, unawareness and misinformation surrounding sleep studies.

This article aims to demystify sleep studies so you know what to expect if you want to make a positive step towards understanding and treating sleep apnea.

What does a sleep study do?

A sleep study does exactly what the name suggests, it studies your sleep. This is done via a process called polysomnography (PSG) which literally translates to “many sleep measurements”.

Sleep apnea cannot be diagnosed with your snoring sounds on their own, therefore other measurements are necessary. As well as capturing your sounds with a microphone, PSG will also measure:

  • Blood oxygen levels – blood oxygen drops during apnea episodes.
  • Brain activity – to detect the microarousals that accompany apnea events and assess sleep stage.
  • Muscle activity
  • Heart rate
  • Breathing rate and effort – to provide evidence of breathing interruptions.
  • Eye movement – helps to determine what stage of sleep you are in.
  • Sleeping position – gives some insight into what triggers sleep apnea.

PSG can also be used to study other conditions such as narcolepsy, restless leg syndrome, periodic limb movement disorder, insomnia, sleepwalking and night terrors.

How do I get a sleep study?

Medical referral

If you think you might have sleep apnea, first assess your risk with some questionnaires. Scoring high on screening questionnaires such as the STOP-Bang questionnaire and the Epworth Sleepiness Scale can be useful in persuading clinicians that a sleep study is necessary.

You can then see your doctor to request further investigation into your sleep breathing problems.

As well as your screening questionnaire results, SnoreLab can often be very helpful in giving your doctor some evidence of your loud snoring or maybe even some apnea episodes.

If seeing a general practitioner for your initial consultation, you may first be referred to a sleep specialist or an ear, nose and throat (ENT) clinician before being offered a sleep study.

Requesting a home study online

In some countries, there are online companies that conduct home sleep studies without you ever having to attend a medical consultation. After filling out an online assessment form and paying a fee, these companies will post your study equipment to you with instructions.

Which type of study is best for me?

If your specialist deems you to be at risk of sleep apnea, you should be offered a sleep study to confirm this suspicion.

There are two types of study, one done at a specialist sleep lab, the other in your home.

Studies done at sleep labs:

  • Give more reliable insight into what is happening to your body during sleep
  • Use more attachments and measurements; can detect a wider variety of conditions
  • Are usually more expensive
  • Often have less availability meaning longer waits

Whereas studies performed at home:

  • Are more comfortable due to the familiar settings, therefore can give better quality sleep
  • Still give reliable results, particularly if your symptoms are quite severe
  • Are usually less expensive
  • Are more convenient
  • Can be prone to error if not fitted correctly

Often, your specialist will recommend the most suitable type of study for you and will make you aware of the relative merits of each.

Sleep lab studies – what to expect

Sleep studies conducted at specialist labs are more comfortable than many people think. The word “lab” conjures images of cold indifference; people in white coats and unfriendly, clinical surroundings. Most bedrooms in specialist sleep clinics are comfortable and sympathetically decorated, with a real bed as opposed to a hospital trolley – some say akin to a three-star hotel.

Before your study

To ensure good sleep and reliable data, there are a few things to do in the lead up to your study:

  • Maintain a normal and healthy sleep routine on the nights leading up to the study.
  • Avoid napping on the day of the study.
  • Limit caffeine consumption and avoid alcohol altogether.
  • You may also need to adjust your medications (ask the referring specialist beforehand).

What to bring

Make sure to bring:

  • Suitable night clothing
  • A change of clothing for the next day
  • Toiletries
  • Something to keep you occupied before going to sleep. There will likely be a period of winding down before the study starts, so a book or puzzle to keep you occupied (without excessive stimulation) is a good idea.
  • Any medication you take routinely, both to maintain that routine and to show to the staff, as this can provide some insight into your sleep symptoms.
  • Any necessary documentation

Getting wired up

Because PSG measures many different things, there are lots of attachments that need to be made. Ultimately, you need to be relaxed enough to sleep properly, so the technician should take time to make sure the attachments are secure yet comfortable. This will take anywhere from thirty minutes to an hour, so you should use this time to ask any questions you have.

Different labs will vary, but typically you will have these various attachments on a number of places on your body:

  • Head – electrodes taped on to measure your brain activity.
  • Side of your eyes – these measure the movement of your eyes to help determine your sleep stage.
  • Chin – electrodes here assess the muscular tension in your jaw.
  • Nose – a nasal cannula rests two small tubes into your nostrils to measure breathing rate.
  • Chest – a strap here monitors your breathing effort. This part may also include a small box where other channels are connected to.
  • Finger – a small clamp usually on your index finger measures blood oxygen levels by shining infra-red light through your finger nail.

Once all of these attachments are in place, your technician may ask you to blink or make some snoring noises to test the connections.

You are likely to then be given some time to wind down before going to sleep.

Depending on the time of your study and the individual practices of different labs, you may be provided with a meal.

Getting to sleep

As more and more pieces of wire are attached to you, you’ll probably feel that it’s less and less likely that you’re going to be able to sleep in this strange environment.

People often start to worry that they won’t sleep or get accurate results. In reality, only a tiny proportion of sleep tests fail due to inadequate sleep data. It may take a little longer to fall asleep, but usually, you’ll get plenty of sleep which will give the clinicians lots of data to work with.

Throughout the night

Typically, you are given six to seven hours to sleep. A technician will monitor you overnight. If you need to urinate in the middle of the night, simply let the technician know and they will come to disconnect the relevant attachments properly.

In the morning

Don’t be surprised if you wake up to a different technician. Sleep studies last about ten hours from initial arrival so it’s likely that the staff will change over.

Once you have been given time to change and freshen up, you might be asked to complete some questionnaires about your sleep and symptoms. Everything is usually done by 7am.

Home studies – what to expect

Typically, you will have your home sleep study about four weeks after your initial referral.

Attaching the equipment

If you have booked your home study through a clinic, you will probably have to attend that clinic on the day of your study. This is your chance to get as much information as you can and ask any questions if you have them. There are two possible set-up methods, you will either:

  1. Collect the equipment and attach the components yourself once at home. Here, you will be given the home study equipment with a set of instructions. These types tend to have fewer pieces and therefore give less detail
  2. Get the main components attached by a technician with just a few connections for you to do once home before you go to sleep. Having a specialist fit the components allows use of more connections giving more measurements.

If you have mobility issues, it may be possible for a sleep technician to deliver and fit the study equipment in your home.

Home sleep studies tend to be less involved than those conducted in specialist labs, so there are likely to be fewer attachments. You will have a minimum of:

  • Nasal cannula – rests two small tubes in your nostrils to assess your airflow.
  • Finger clamp – this is a pulse oximeter: a device that measures the amount of oxygen in your blood.
  • Chest strap – this measures your breathing efforts as well as containing a box where the other wires connect.
  • Heart rate monitor.

This is the minimum. Some home studies, particularly those where a specialist gets you fitted at the clinic beforehand, have more attachments that can also measure brain, eye and muscular activity; much like a lab study.

Getting to sleep

Once wired up, despite being in the comfort of your own bed, you are likely to take a little longer to get to sleep. Most people report that the attachments feel a little strange but not uncomfortable. The set-up should allow you to sleep in whatever position you like.

If you worry that you aren’t sleeping enough, remember that only a tiny handful of sleep studies fail due to inadequate sleep data. Though you may feel you haven’t slept particularly well, chances are, you slept much more than you think you did.

In the morning

Most equipment is quite easy to disconnect. Clinics don’t usually require the parts to be bundled up neatly and often supply a simple plastic bag or box for you to simply stuff the parts into. Usually, the cannula is disposable.

Some units will have a little light that shines either green or red in the morning to indicate whether the test has sufficient data. You’ll be given instructions before as to what to do if the light is red.

You then need to return the study to the clinic for them to generate the results.

To better understand what happens in a home sleep study, read Susan’s story, a SnoreLab user’s first-hand account of getting a sleep apnea diagnosis through a home sleep study.

Understanding your results

Getting your sleep study results back can take days to weeks. If you have had a home study and your results are unclear, your specialist may refer you for a lab study instead.

You will get a document that gives many details about what was recorded during your study. Here is a breakdown of what usually gets measured and what it all means …

Sleep physician/technician’s report

This is a summary of the findings. They will say whether your sleep and the data obtained was adequate as well as an overview of the findings including: sleep position, sleep stages and apnea episodes.

Calculated variables

These are your apnea measurements:

  • Total AHI – the average number of times per hour, you experienced an apnea or hypopnea event (total or >50% breathing cessation for 10 seconds or more).
  • NREM AHI – the AHI during the non-REM stage of sleep.
  • REM AHI – the AHI during the REM stage of sleep.
  • Minimum oxygen saturation – the lowest level of oxygen detected in your blood.
  • Longest apnea – the duration in seconds of your longest period of complete breathing cessation.
  • Longest hypopnea – the duration in seconds of your longest period of partial (>50%) breathing restriction.
  • Mean apnea/hypopnea duration – the average time in seconds of each episode.
  • Arousal index – the number of times per hour you aroused from sleep.
  • Apneas experienced in different positions


This identifies if you have sleep apnea and its relative severity:

  • Normal: AHI = 0-5. This will sometimes just be called “primary snoring”.
  • Mild obstructive sleep apnea: AHI = 5-15
  • Moderate obstructive sleep apnea: AHI = 15-30
  • Severe obstructive sleep apnea: AHI = 30+

Sleep statistics

These are the measurements of your sleep, the relative times spent in each sleep stage and how long you took to fall asleep:

  • Time available for sleep – i.e. when the lights were off.
  • Total sleep time
  • Sleep efficiency – this is the percentage of time spent asleep during the time that the lights were off
  • Sleep latency – the time taken to fall asleep
  • REM sleep time
  • NREM sleep time
  • Sleep in supine position – time spent sleeping on your back.

Different sleep stages with SnoreLab’s insights into the Architecture of Sleep.

Learn more.

The next steps

Your results report may also include some recommendations. If your results show little to worry about (i.e. normal primary snoring) you’ll get some general advice that takes into account both the study results and your general health.

If sleep apnea has been detected and you had your study through a referral process, you will then have some follow up appointments to discuss treatment options.

Mild to moderate sleep apnea can often be improved with consumer anti-snoring remedies and positive lifestyle changes. Usually, severe sleep apnea requires treatment with CPAP.

See SnoreLab’s guides to the different types of CPAP mask and how to fix common problems with CPAP.

This article gives an overview of the general processes in most laboratory and home sleep studies. Individual practices may vary.

The Architecture of Sleep

Science, Sleep

The Architecture of Sleep

If you have ever been suddenly woken up, deep into the night, you’ll know it’s a very disorientating experience. When you wake up naturally, you rouse gently in a less confused state. This is because in these separate instances you have woken up in different stages of sleep.

Sleep has two main states, these are crudely defined by the movement of our eyes (but actually have a lot more important qualities and differences):

  • Non-rapid eye movement (NREM)
  • Rapid eye movement (REM)

Having the correct proportions of each of these types is important to getting good and restful sleep.

The Sleep Cycle

Going from being awake to sleeping isn’t like flicking a simple on/off switch. Sleep has different stages and depths where your brain and body go through specific motions.

Within the seven to eight hours that we should be sleeping, we cycle through these NREM and REM stages in ninety-minute blocks …

  • To start, we initially plunge quickly through the stages of NREM sleep and trundle along in deep sleep.
  • After a while, we climb back into lighter NREM, eventually spending some time in REM.
  • We then drop back into deep sleep again at the start of the next ninety-minute cycle.
  • For every cycle, an increasing amount of time is dedicated to REM sleep, creating an asymmetric pattern.

But what happens during these phases, and why are they necessary?

NREM vs. REM Sleep

NREM Sleep

Stage 1 – this is light sleep, the first destination after wakefulness with tiny dream-like thoughts and easy arousal back to being awake.

Stage 2 – here, breathing slows and body temperature drops.

Stages 3 and 4 –this is deep sleep. Any sound, touch or light from the outside world is tightly controlled, with entry to the brain blocked. This is why it is hard to rouse someone from deep sleep.

This is an important stage for growing and repairing the body, increasing blood flow to various tissues, releasing important hormones and re-energizing.

The brain is reviewing the information that it has received throughout the day. Without the mental chatter of consciousness, our brain waves are long, slow and coordinated.

This pattern allows effective communication between different brain regions. Information is selected and pruned to form memories; the important memories being retained by creation of pathways in the brain, whilst needless ones are discarded from our temporary and fragile short-term storage.

REM Sleep

REM sleep is our dreaming sleep. Despite being asleep, our brain activity is very similar to when we are awake – lots of action; short, sharp and cluttered waves of electrical activity.

The exact functions of REM sleep are still not fully understood, but it is thought to be important in memory formation and learning. The memories selected in NREM sleep are now played back to us, helping us contextualize, learn and integrate them into the real world.

Despite being close to waking, our bodies are completely still, a mechanism to prevent us from turning this pseudo-consciousness into potentially risky sleep-walking or acting out dreams.

When deprived of REM sleep, both mental and physical dysfunction ensues. Indeed, when falling asleep after a period of REM deprivation, our sleep cycle patterns shift to snatch back as much of it as possible, favoring longer periods of REM sleep [1].

Side note: Extreme sleep deprivation and REM

In 1959, radio presenter Peter Tripp staged a “Wakeathon” as a publicity stunt. He stayed awake and on-air for 200 hours straight. As he became more and more sleep deprived, his brain started to enter REM sleep whilst being awake – he was dreaming with his eyes open. Tripp started to think he was an imposter of himself. During a bathroom break he opened a drawer which spat out flames, and he thought his assistants were conspirators trying to frame him for a crime he didn’t commit.

Where does snoring come into this?

There are no definitive rules as to when snoring and sleep apnea occur during the sleep cycle, but studies have found certain trends. It is thought that regular snoring occurs more during NREM sleep. This would explain why snorers don’t wake themselves up with the sound of their own snoring.

Obstructive sleep apnea is commonly associated with REM sleep [2], despite this some studies have found just as many cases of worsened apnea during NREM sleep [3].

Why Good Sleep is Important

Science, Sleep

Why Good Sleep is Important

The partner of a chronic snorer loses over an hour of sleep every night [1]. Good sleep can be hard to come by for all parties in a bedroom polluted with snoring, particularly if snoring transitions to sleep apnea.

But why does this matter?

Sleep can seem like a real waste of one third of your life; time spent doing apparently nothing when there’s so much else you could be doing. A lack of sleep however, spells a shortened life and one where your waking hours are severely blunted.

By staying awake and spurning sleep, more time is lost than is gained. We must accept that sleep is vital for health and survival.

Good sleep is healthy

Sleep seems to be a pretty inactive period. On the surface, our sincere lack of movement or responsiveness would indicate that our body is dormant. This isn’t so. It’s very active, just in a different way. During sleep, our bodies and brains are busily repairing, refreshing and rewiring.

If sleep were a miracle drug, everyone would pay a fortune for it as the list of benefits are nothing short of astounding. Sleep:

  • Reduces your risk of chronic physical, neurological and mental disorders
  • Enhances your defenses to infection
  • Diminishes food cravings helping to regulate weight
  • Forms new memories

Good sleep can even make you look better. Cortisol – a stress hormone – increases when we lose sleep and in turn decreases the production of collagen, a protein that gives your skin smoothness.

A study in Sweden asked volunteers to rate the attractiveness of people who had 8 hours sleep against those who had experienced 31 hours sleep deprivation. The sleep deprived people were perceived as less healthy and less attractive [2].

Bad sleep is damaging

The inverse of the advantages of good sleep is the damage that can be done with sleep deprivation. Indeed, multiple studies have shown that getting less than six hours of sleep per night significantly increases the likelihood of an early death [3].

In the short-term, the mental impairment from moderate sleep deprivation equates to the effects mild alcohol intoxication [4]. Extreme sleep deprivation has even been shown to cause hallucinations.

Over a longer period, chronic sleep debt can do irreversible damage to the brain and rest of the body. Importantly, this increases the likelihood of a host of maladies:

  • Stroke
  • Anxiety and depression
  • Dementia
  • Weight gain
  • Heart disease
  • Reduced immunity
  • Cancer


Poor sleep is the underdog of public health. Problems like obesity, cancer and dementia are far more prominent in the public consciousness than problematic sleep is. If you consider that bad sleep has a hand in all of these conditions, you’ll appreciate the importance of getting a good night [5].

If snoring is having an impact upon the sleep quality of you or your partner, these nighttime noises definitely need addressing.

Body Clock: Sleep, Light and Melatonin

Science, Sleep

Body Clock: Sleep, Light and Melatonin

Have you ever wondered why you feel sleepy at night and awake in the day? This daily fluctuation is your natural body clock working correctly. Humans are naturally diurnal, meaning that we are meant to be active whilst it’s light, and should go to sleep when it’s dark.

Eyes and the brain

Our eyes don’t work very well in the dark, so it makes sense that we use this time to sleep and recover. Our feelings of sleepiness or wakefulness are dictated by light and what it does to our brains.

When light hits the back of our eyes, a cascade of information zips through the brain, telling a small gland deep in its center to stop the release of an important hormone, melatonin. When light diminishes at night the brakes are taken off. This hormone, sometimes nicknamed “the vampire hormone”, is now released in abundance and sets up our bodies for sleep. Melatonin lowers our blood pressure and body temperature, telling us that now is the time to go to bed [1][2].


Unfortunately, our internal body clock isn’t perfectly matched to the celestial clock of the Earth. Whilst the Earth does a full rotation in twenty-four hours, our body clock exceeds this by about fifteen minutes. Left to its own devices, our brains would switch between nocturnal and diurnal every month [2].

Light and melatonin brings our rhythm back in line with the day/night cycle of our planet. Artificial light can also influence melatonin release which is why SnoreLab uses darker colors.

Jet lag

Now consider long-haul flights, something that nature and evolution didn’t take into consideration. When we travel to a different time-zone, despite changing the clocks on our watches and phones, our body clock takes a bit more time to reset.

With the different patterns of light in far-flung destinations we can slowly coax our clock into synchronizing with our location. In the meantime, we have to put up with the uniquely miserable phenomenon of jet lag.

Let’s imagine we’ve travelled east, it’s 11pm local time but our body is convinced it’s only 4pm. We are not ready for sleep just yet but we try to force the issue, eventually falling asleep at 2am local time. Time to wake up at 7am for an important meeting, but internally, it’s midnight – time to sleep. But now we’ve got to get up and face the day perpetually in a state of groggy under-functionality.

Every day we are in this new environment, the new light pattern we are exposed to brings our rhythm back in line by about an hour. It will therefore take roughly seven days to fully get over this seven-hour difference [3].


Jet lag isn’t the only shift in our internal cycle. Melatonin’s daily pattern changes throughout life. During adolescence, its release is delayed to later in the night which is why teenagers go to sleep and wake later. As we age, melatonin production diminishes, meaning we wake up earlier and generally sleep less [2].


Light, or lack thereof, is vital for good sleep hygiene, and good sleep hygiene keeps exhaustion and snoring at bay. When you set SnoreLab before bed, make sure it’s the last thing you do with your phone at night.

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