My understanding of narcolepsy in humans is that it can happen at any time,
even when they are somewhat occupied.
With some horses, they doze off normally and then fall down and wake
up with a start.
What I have been told is that some horses who have been diagnosed with
narcolepsy aren't narcoleptic at all but rather, have a problem in their leg
joints with the locking mechanism that allows prey animals to sleep standing
up. Their legs joints don't lock efficiently and reliably in their sleep
the way they should.
I know a former race horse who does this. It happens every once in a
while and doesn't seem to have much to do with what kind of night's sleep he's
had. He'll doze off in the day and fall to his knees and wake up with a
start, jumping up and looking around. He's 21 and used to it so he
immediately goes about his business....
