Title: Re: Horse falling while sleeping
This is much different from simply lying down to sleep (although I had appys who liked to do that too). I had an appy mare with narcolepsy. Got worse as she got older. She would be in cross ties, being groomed prior to being ridden, would fall asleep and just keel over. I mean she would fall flat on her side. Boom. Would wake up seconds later, prone, looking up at you with a curious expression on her face: 'how did I get down here?''
Very, very dangerous.
I'd find a vet willing to look into treatments for possible narcolepsy. There have been several articles lately (say in the last year) in either 'Equs' or 'Horse Illustrated'.