Just an anecdote that proves nothing: I lose consciousness instantly if I laugh at something unexpected and really funny. I drop like I've been pole-axed and I'm out cold for a few seconds. I only realize it has happened after the fact. Apparently my condition is called laughter syncope. I'm guessing I'll probably die laughing. Hopefully I won't take anyone else with me.
Needless to say, I don't drive often, and I avoid NPR and bumper stickers when I do.