Impact of naps and caffeine on extended nocturnal performance.

It was hypothesized that alertness and performance during an extended work period would be improved by an afternoon nap and the subsequent use of caffeine during the night. Twelve young adults received a 4-h afternoon nap and caffeine during the night during one session and four 1-h naps during the night in a second session. After an afternoon nap, subjects had increased objective and subjective alertness, increased oral temperature, and increased performance on complex tasks like logical reasoning and correct additions when compared to the condition that allowed four nighttime naps. It was concluded that the specific scheduling of a nap period in preparation for an all-night work shift where sleep would not be allowed could result in increased alertness and performance as well as a less conflicted work situation.