A pilot study investigating the impact of a caffeine-nap on alertness during a simulated night shift.

Consuming coffee immediately prior to a nap, known as a caffeine-nap, has been shown to improve alertness during the day, but it is unknown whether a caffeine-nap is effective at reducing sleep inertia during the night. A simulated shiftwork cross-over laboratory study was conducted whereby participants (N = 6, 4 F, 21-36y) consumed 200 mg of caffeine, or decaffeinated coffee (placebo), immediately prior to a 30 min nap opportunity at 03:30 h. Compared to placebo, the caffeine-nap resulted in improved vigilant attention and subjective fatigue in the 45 min post-nap opportunity. The caffeine-nap may be useful in reducing sleep inertia in shift workers who nap on nightshift.