The Alerting Effects of Caffeine, Bright Light, and Face Washing After a Short Nap
Summary
This randomized crossover study tested how different strategies influence alertness after a short daytime nap. Ten healthy adults completed five nap conditions: nap only, nap plus 200 mg caffeine, nap plus one minute of bright light, nap plus face washing, and no nap (rest only). The combination of caffeine and nap produced the strongest and most sustained improvements in both alertness and task performance. Bright light after a nap was nearly as effective for reducing subjective sleepiness but less effective for performance. Face washing provided only a brief reduction in sleepiness immediately after the nap.
Why It Matters For Night Shift Workers and Night Owls
This study shows that short naps can be made more effective with simple countermeasures. Taking caffeine before a nap provides the most reliable improvement in alertness and performance, while brief bright light exposure after a nap can also extend the benefits. Even face washing gave a temporary lift, though its effects were limited. For night-shift workers, combining a nap with caffeine or light offers a practical way to stay alert during the most fatiguing hours.
Notes
Older but still‑cited lab study.