What are the symptoms of sleepiness?

Dr. Rosekind: You know, I tell everybody that if you're walking around noticing that you're having to read that paragraph for the third time, or somebody just gave you a phone number and you can't remember the last couple of digits, or that you were a little more edgy in that conversation, a little moodier and angrier and more upset than you needed to be, or you're in a big business deal and all of a sudden your decision-making is way off—all of these are signs and symptoms that you need to get some sleep, whether that's a full night's sleep or a strategy like taking a nap if you need to.

How effective is napping in combating the effects of fatigue?

Dr. Rosekind: One of the most effective strategies to improve alertness is a short nap. When I was at NASA we conducted a study in which we gave pilots planned, controlled 40-minute naps in the cockpit to see how they affected their alertness and performance. What we found was that performance was improved 34 percent and their alertness was improved 54 percent. I always challenge people to name another productivity tool that's as simple and straightforward to help improve performance, productivity and safety as a quick nap.

The guidelines for napping are that if you are going to take a short nap, make it up to about forty-five minutes. The reason for that is that a slightly longer nap will put you into deep sleep. If you awaken somebody in deep sleep they can be sleepy and groggy and disoriented for a period of time, that's called sleep inertia. So a short nap up to forty-five minutes helps you avoid that by awakening you before you enter the deep sleep phase.

If you're going to take a longer nap, you want to make it about two hours or so to get you through a full sleep cycle. And that's how simple it is to get that kind of performance and safety benefit by having a short nap.