DEAR DOCTOR K: Everybody sleeps, but why is that? What does sleep do for us?
DEAR READER: I get this question a lot, and we've talked about it before in this column. There is some new information that is interesting. The honest answer is that we don't know why it is we sleep. We spend about a third of our lives doing it, so nature must have a reason for it. But it's hard to ask nature questions -- or, at least, to get an answer. One possible reason for sleep is obvious: Our muscles may need the rest. However, the heart is a muscle, and it doesn't rest while we sleep, thank goodness. And like our heart, many of our other organs, such as the liver and kidneys, keep working.