Promoting alertness with a short nap during a night shift

Area of Science:

• Occupational Health
• Sleep Science
• Human Physiology

Background:

• Shift work is prevalent and associated with sleep disturbances and reduced alertness.
• Maintaining alertness during night shifts is crucial for worker safety and performance.
• Short naps are a potential countermeasure for sleepiness during night work.

Purpose of the Study:

• To investigate the impact of short naps (< 1 hour) on alertness during the early morning hours of the first night shift.
• To evaluate the effects of nap duration (30 or 50 minutes) and timing (01:00 or 04:00) on physiological and subjective sleepiness.
• To assess the influence of naps on subsequent daytime sleep quality.

Main Methods:

• Laboratory-based study with fourteen experienced male shift workers.
• Four experimental night shifts: control (no nap), 30-min nap, 50-min nap at 01:00 or 04:00.
• Assessment of visual signal response times and sleepiness levels (physiological and subjective).
• Evaluation of daytime sleep quality following each experimental shift.

Main Results:

• Naps significantly improved response to visual signals in the latter half of the night shift.
• Physiological sleepiness was reduced post-nap (50 min after awakening) but not at the shift's end.
• Subjective sleepiness decreased, but naps induced mild sleep inertia (10-15 min).
• 50-minute naps showed a slight impairment in subsequent daytime sleep.

Conclusions:

• Naps shorter than 1 hour can partially enhance alertness during the initial night shift.
• Nap timing and duration influence alertness and sleepiness, with potential trade-offs with daytime sleep.
• Short naps represent a viable strategy to mitigate sleepiness in shift workers, warranting further optimization.