Sleep Apnoea in Horses

Horses have quite varied sleeping habits. Much of their sleep is done  in a standing position which renders them ready to flee any approaching predator. They do also occasionally sleep either in a sitting position with their chin on the ground or whilst recumbent or laying on their side. It is thought that most of the REM ( rapid eye movement) sleep occurs whilst in this laying position. Horses that for different reasons are deprived of this recumbent sleep may suffer from periods of standing sleepiness and may occasionally collapse. The later has been seen as a form of narcolepsy.

One cause of recumbent sleep deprivation could be the lack of a mate. Horses will normally only recumbent sleep whilst another horse stands guard. Obviously if a predator approaches then its mate will warn / wake it.

Another possible cause is that horses that experience obstruction of the airways during maximal exercise may also have this obstruction occur during sleep. This temporary obstruction would most likely cause an interruption to normal breathing (apnoea) and the horse to wake up suddenly. If this continued to happen then a horse is unlikely to assume a sleeping  position in which its sleep is continually disturbed. On several occasions it had been observed that prior to surgery for obstructive upper airways problems horses did not or at least rarely slept in a recumbent position. Within 10 days of surgery these same animals were observed to regularly sleep in a recumbent position and closer observation revealed regular movement of the eyeball below the eyelid.

Does your horse occasionally sleep in a recumbent position ?

If your horse suffers from collapsing episodes (narcolepsy) or severe drowsiness, have you observed these periods of recumbent sleep?

Yes / No    How often?

Did your horse have a companion leading up to this event?

Yes / No

If not seen in recumbent sleep then does it sleep in a sitting position instead?

Yes / No

Please e-mail me with your observations.

Further Reading

1) Sleep Patterns in Horses

    If your horse dozes off between classes at a horse show, does that 

    mean he's exhausted? Probably not.

    By - Sue McDonnell  in Practical Horseman 2000

2) The Domestic Horse , The evolution, Development and Management

    of its Behaviour.

    Editors - Daniel Mills & Sue McDonnell.

3) Is Your Horse Sleep Deprived?

    The answer may surprise you, according to a veterinarian who has 

    investigated how physical or mental discomfort can leave a horse

    sleep deprived and too tired to stay on his feet.

    By Christine Barakat  - February 2007 issue of EQUUS magazine.