My boss did a sleep study very recently, 2 nights of it.
They found out he had a severe case of sleep apnea, which is why he's been coming in late for a while now everyday (though he does stay till very late as well).
They claim he stops breathing 20-30 times a night and that he's lucky he's been living so long. Now he sleeps with one of those facemasks which he says is ridiculously uncomfortable till he gets used to it. It forces air into his nostrils basically (high enough pressure that you feel it).
On top of this, he gets severe allergies during Spring and Fall, so for the last couple of months, he'd have his sinus problems and along with this mask, the pressure just shifts over to the other nostril, so he can't even sleep with it on now.