Sometimes in the afternoon I take a nap to feel fresh for evening classes. However, when I wake up,. I'm often very nauseated and wish I'd just stayed awake. Other people have told me they feel the same. How can sleep make you nauseated?
-- JM, San Diego
Sleeping hardly ever makes yours truly sick. On the other hand, getting out of the sack has ruined an otherwise promising day. So just snooze through that class, J, and your problems are solved and I can get back to nurturing my close personal relationship with Morpheus, uninterrupted by the whines and badgering of perplexed San Diegans.
Okay, as long as I'm up, here's your answer, or at least the best medical guess. Normally our bodies work in a cyclical pattern of waking and sleeping, a co-called circadian rhythm. When we feel drowsy at night, various body functions slow down. This includes digestion and the related saliva production. During the hours when our bodies expect us to be charging around getting things done, these functions are usually working at peak efficiency. So when you throw a wrench in the works by dozing off after lunch, your stomach is still churning away. And it's also trying to digest lying on its side, perhaps forcing stomach acid and contents back into your esophagus. Nature's way of telling you to cancel that evening class. Our circadian rhythm also explains why we drool all over the pillow in the afternoon but usually not when we sleep at night.