It's a common question to ask someone about their sleep habits or to express concern for someone who might not be getting enough sleep.
Here are some example sentences:
* ¿Como duerme usted? (How do you sleep?)
* Mi hijo no duerme bien. ¿Como duerme el tuyo? (My son doesn't sleep well. How does yours sleep?)
* Me preocupa como duerme mi abuela. (I'm worried about how my grandmother sleeps.)