Napping: Helpful or Harmful? The Pros and Cons of Daytime Resting(Napping: Helpful or Harmful? The Pros and Cons of Daytime Resting )

Getting some sleep, even a short afternoon nap, may seem like a good thing for people with sleep disorders. But for those with insomnia and an already decreased desire to sleep at night, midday shut-eye can actually be counterproductive. So before you curl up on the couch this afternoon, consider whether your quick fix might backfire when you lay down in bed tonight.

Naps can get you through the day...

If you don't usually have a problem getting your Z's at night, a quick nap can work wonders to pull you through an exceptionally tiresome or sleep-deprived day.

In fact, a 2008 City University of New York study found that a 45-minute daytime nap can improve memory function. And previous studies have found that short afternoon siestas can lower blood pressure, and even seem to reduce the risk of death by cardiovascular events.

Those who suffer from narcolepsy or shift-work syndrome—where your sleep-wake patterns are out of sync with everyone else's, may also benefit from daytime naps, says James Wyatt, PhD, director of the Sleep Disorders Service and Research Center at Rush University Medical Center in Chicago. "Fifteen minutes can keep you going for hours," he says.

…But not if you have trouble sleeping at night

If you've got insomnia, however, naps present a problem. Assuming you even feel sleepy during the day (insomniacs often don't), napping reduces your chances of sleeping a full night. Even for people with temporary sleep issues caused by stress, illness, or even jet lag, napping during the day can perpetuate bad sleep habits, confuse your internal clock, and send your insomnia into a chronic spiral.

"Even just a little bit of a power nap reduces your nighttime sleep drive," says Ralph Downey III, PhD, director of the Sleep Disorders Center at Loma Linda University Medical Center in California. "The nap becomes nothing more than another episode of fragmented sleep."

If your schedule allows for it and you don't mind splitting up your sleep between day and night, an afternoon snooze is fine, says Wyatt. Older adults and retirees—or those who are self-employed—for instance, may enjoy napping if they have time to spare during the day, and don't mind being up at night. "But for most of the population, there's no napping with insomnia," he says. "Not if you want to get all of your sleep at night."

The urge to nap could also be a warning sign

If you're constantly fighting (or giving into) the urge to sleep during the day and falling asleep instantly at night, you might have obstructive sleep apnea, a condition in which you stop breathing while you sleep.

In this case, naps won't help; in fact, you'll wake up just as tired, since your lungs are deprived of oxygen anytime you doze off. By wearing a continuous positive airway pressure (CPAP) machine that flows oxygen through your nose, however, you'll likely sleep more soundly and wake refreshed—whether from a good night's rest or a quick catnap.