All the facts about sleep-sneezing, sleep-yawning, and sleep murder.

Hey, Matt:

What's the relation between sneezes and yawns, two bodily functions that won't happen in one's sleep?

-- Tired, with a Cold

I assume you've kept one eye open at night, so you're positive you don't sneeze or yawn. I mean, this is verifiable data we have here, yes? No. Sneezes and yawns are perfectly doable in our sleep. Or in a coma, for that matter. And what sneezes and yawns have in common explains the situation. Both are involuntary reflexes that are mediated by the brainstem. That's the most "primitive" part of the brain, which controls things like breathing, heartbeat, digestion-- basic life-and-death stuff. No thinking is required in this area, so sneezing and yawning might occur any time the brainstem is ticking along. It's not uncommon for someone in a coma to yawn as a prelude to regaining consciousness, according to Dr. Doctor, our staff medico. A sneeze is just a response to a nasal stimulus. No fancy rationale needed.

It shouldn't be a surprise that we can do something simple like yawn in our sleep. Consider all other the strange stuff people do: talk, walk, sit up and look around, yank all the blankets to their side of the bed... I went snooping for some instructive stories of sleep activities and found the tale of a woman who made and then ate a late-night snack of cat food sandwiches and buttered cigarettes. Physicians say sleep-driving isn't unheard of. Better yet, there have been at least 30 murder trials in which the defendant claimed to be sleepwalking at the time. One man in Canada fell asleep on his couch, then got up and drove 14 miles to his in-laws' house, bludgeoned and stabbed them, cut himself badly in the process, then drove to the police station and confessed. When he woke up in the hospital, he claimed to remember none of it. His attorney offered evidence that the man fit the profile of a sleepwalker, came from a long line of sleepwalkers, and had a history of sleepwalking. Not guilty, said the jury.