Once people find out I work overnights [Mid-5:30 am, weekdays] here at the New 96.1 Joy-FM, they usually ask me how I can sleep during the day. I wish I had a better answer than the truth, which is: I've just always been able to. Then again, sleep in general is pretty mysterious.

I mean, researchers admit they really don't know why or how sleep works. Michael J. Twery, PhD, director of the National Center on Sleep Disorders Research, says that it's only been in the last decade or so that researchers have learned "..sleep is biologically programmed into virtually every single cell of your body."

We do know that sleep does many important things for us. In addition to refreshing the body, it plays a role in learning and memory, as well as growth, development, and even immunity. It appears that these different activities take place during different part of a night's [or day's] sleep. But no one is exactly what part of your sleep is most important for you. The key, according to experts, is to get the amount of sleep you need.

How much is "enough" sleep? For most adults, seven to nine hours seems to be about right. But you may need more, or less. Try sleeping some night when you have nowhere to be the following day, then see how long it takes for you to wake up. Lawrence Epstein, MD, chief medical officer of Sleep HealthCenters, calls alarm clocks "...the best way to sleep deprive yourself."

Do you have trouble sleeping? If it's only occasional, it's probably nothing to worry about. But if you regularly feel tired, you should check with your doctor about possible causes.