A parasomnia is an undesirable physical or experiential event that accompanies sleep. They can occur as movements, emotions, perceptions, and dreams. Changes in the autonomic nervous system with skeletal muscle activity are features of a parasomnia, and it is not uncommon for a patient to experience more than 1 parasomnia.

It is easier to identify a parasomnia if you can determine when it is occurring during sleep.  Parasomnias that occur during non-REM sleep include confusional arousals, sleepwalking, and sleep terrors. Those that occur during REM sleep include REM sleep behavior disorder, recurrent isolated sleep paralysis, and nightmare disorders.

Parasomnias that occur in non-REM sleep, such as sleep walking and night terrors, are often seen in children. Wake a child from this stage of sleep and you are likely to see confusional arousal as well. Patients will be disorientated and may have slow speech. It is also unlikely that they will remember that they were awakened and easily fall back to sleep.

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Parasomnias that occur during REM sleep are often seen in older patients.  Patients with REM sleep behavior disorder are more likely to be over 60 years of age. Sleep paralysis can happen at any age, but it usually presents  in young adults. Nightmares can also be seen at any age, but night terrors tend to occur in those a little older.

Parasomnias occurring in non-REM sleep occur more frequently in the early stages of sleep.  Sleepwalking, for example, occurs during the first half of the sleep period. Patients can exhibit very elaborate behaviors and may not remember anything that occurred during the event.  Sleep talking, on the other hand, can occur in non-REM and REM sleep.

Parasomnias that occur later in the night are often associated with REM sleep. REM sleep occurs about every 90 minutes, but each REM stage gets longer as the night goes on. The last REM stage can last for an extended period, so the chances of a REM-sleep parasomnia are greater in the later part of the night.

When assessing which parasomnia may have occurred in a patient, first determine when it occurred during the night and it might help you with your diagnosis. Some are easier to determine than others. It is pretty easy to diagnose sleep walking, but it may be more of a challenge to determine a nightmare vs a sleep terror.

In the coming weeks, I will write more about these interesting parasomnias! Stay tuned.

Sharon M. O’Brien, MPAS, PA-C, is a practicing physician assistant and health coach in Asheville, NC. 


  1. Kryger MH, Roth T, Dement WC. Principles and Practice of Sleep Medicine. 4th ed. Elsevier Health Sciences. 2005.