DEAR DOCTOR. K:

As I've gotten older I don't sleep as well as I used to. I'm retired, so I have the time to take an afternoon nap. But I'm worried that if I sleep during the day, I'll have even more trouble sleeping at night. What do you think?

DEAR READER:

I'm not surprised that you don't sleep as well as you used to. Our sleep changes as we get older.

After about age 60, we have less deep sleep. We awaken more often and sleep an average of two hours less at night than we did as young adults.

It was once thought that older people didn't need as much sleep as younger ones. But that's not the case; we need it just as much. We just have a harder time getting it.

Regardless of age, we typically need seven and a half to eight hours of sleep to function at our best. So if you're not getting enough sleep at night, what about daytime naps? Or, as you asked, does napping disrupt the sleep cycle? Will napping ultimately lead to less sleep and more daytime drowsiness?

Everybody's different, and napping is both good and bad, depending on who you are. If you have trouble sleeping nearly every night, and as a result feel tired during the day, napping in the evening is a bad idea. Evening naps make it harder to fall asleep at bedtime. Long naps at any time of day often make you sleep less soundly that night.

On the other hand, suppose you have an occasional bad night's sleep. Maybe there is stress at work, or child-care demands or a noisy neighbor. Whatever the cause, a nap the next day can be a good idea. It doesn't disrupt your nighttime sleep, and increases your total sleep time. That's true whether you take relatively short 45-minute naps or longer two-hour naps.

If you're a shift worker, frequently shifting the time of day when you go to sleep can throw off your sleep cycle. Napping usually is helpful, because it increases your total sleep time.

And napping provides an additional bonus: It helps you think and function better. That's because napping increases the time you spend in the phases of the sleep cycle that help restore the body and brain.

We have a lot more information on sleep, sleep cycles and insomnia in our Special Health Report called "Improving Sleep: A Guide to a Good Night's Rest." You can find out more about it at my website.

As I mentioned, most people sleep less well as they get older. But if your sleep problems are more serious than that -- if they're disrupting your ability to think clearly and function effectively during the day -- then talk to your doctor. There are doctors who are sleep specialists. Your doctor may refer you to one of them.

Otherwise, treat yourself to an afternoon nap. You're likely to sleep more and feel better.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.AskDoctorK.com.)

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