Sleep Study Report Interpretation

This field of sleep disorders and treatment can be overwhelming. It is our goal to provide you with the knowledge and resources to make it simple.

Many times patients can get a copy of their sleep study results, but have no idea what to make of the report. This will give you a basic understanding of sleep terminology and what your diagnosis actually means. Use our Sleep Study Report Interpretation guide and videos below to gain a better understanding of your sleep study and your sleep study report.

How To Interpret Sleep Study Results:

Get a copy of your actual sleep study, not the dictated report from the physician, but the actual data from the scored report.

Sleep Architecture is the term used to describe your make-up and progression of sleep stages. In a normal healthy adult you will have 5% Stage 1, 50% Stage 2, 20-25% Stage 3, and 20-25% REM sleep.

It is very likely that if you’ve had a sleep study for suspected Sleep Disordered Breathing, that your percentages are way off. If it’s your first night of using CPAP it is also very likely you have very skewed percentages. (Increased REM is “REM Rebound” since your body is trying to make up a sleep debt)

It is also normal to have very little if any Delta Sleep (or Slow Wave Sleep or Stage 3) if you are 40-50 years of age or older. Young children have 50% or more Delta Sleep that decreases as we age.

Sleep Architecture Terms:

TRT: Total Recording Time. This is the time from when the technician says Good night, Lights Off, to when they come in the turn the Lights On.

TST: Total Sleep Time. The amount of time that you slept (in minutes) in the time between Lights Out to Lights On.

SE: Sleep Efficiency. Total Sleep Time divided by Total Recording Time. It’s just a percentage of sleep for the time that you were given to sleep.

SOL: Sleep Onset Latency. Time from when the Technician said “Good Night/Lights Off” to the first 30 second page of sleep. In simpler terms is the answer to how long it took you to fall asleep.

Arousal: When you wake up. You may or may not be aware of your arousals. They can be caused by breathing anomalies, leg movements, or for no obvious reason (spontaneous)

REM latency: The time it took you to enter REM sleep once you had your first 30 second page (epoch) of sleep. Normal REM latency is 60-90 minutes, though it is normal in the sleep lab setting to have a 120 minute REM latency.

Sleep Disordered Breathing Terms:

OSA: Obstructive Sleep Apnea. When you stop breathing, but the belts around your chest and stomach are still moving. Your stomach and chest moving tells us that your body is trying to breath (respiratory effort or respiratory drive), but there is an obstruction causing the air to not get through. This could be a large tongue, large uvula, excess tissue in upper airway (fat), small airway, or some other reason. These typically result in an arousal (an awakening). An arousal usually results.

CSA: Central Sleep Apnea. When you stop breathing, and the belts around your chest and stomach aren’t moving. When your stomach and chest don’t move means that your body isn’t even trying to breathe. There is no respiratory effort. Sometimes seen as Cheyne-Stokes respiration. This is a waxing and waning of all respiratory signals.

MSA: Mixed Sleep Apnea. This is a hybrid of Central and Obstructive Sleep Apnea. There is no breathing, but there is a period where the chest and stomach belts are moving, and a period where they aren’t moving. These are seen as the same as OSA. An arousal usually results.

OSH: Obstructive Sleep Hypopnea. This is when breathing shallows and causes your blood oxygen level to drop 4% or greater. An arousal usually results.

RERAS or UARS: Respiratory Event Related Arousals or Upper Airway Resistance Syndrome. Seen as the same as an Obstructive Hypopnea. These have an oxygen desaturation of 3% or less and MUST result in an arousal.

What does all that stuff mean???? All of these are added up to get:

AHI: Apnea/Hypopnea Index. This is the total number of OSA, OSH, MSA, and CSA (NOT RERAS/UARS) divided by the number of minutes slept. Or you could say that it’s the number of Apneas and Hypopneas that occurred per hour of sleep.

RDI: Respiratory Disturbance Index. Same as above, but you also include RERAS/UARS in the calculation.

Your doctor uses these numbers for their diagnosis. ROUGHLY 10-20 is mild, 20-30 is moderate, and 30 and up is severe.

Hopefully the report breaks down the RDI and AHI when on your back (SUPINE) and in REM versus Non-REM sleep. This helps determine if you’re POSITIONAL or REM SPECIFIC with regards to your Sleep Disordered Breathing.

What other stuff is included in the report?

PLM: Periodic Leg Movement. This is when you see at least 4 leg movements in a 90 second period. Each movement would count as a PLM and they may or may not result in an arousal. They have their own index too!!! PLM Index is the number of PLMs seen per hour of sleep (in minutes).

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