Foot cooling does not improve vigilance but may transiently reduce sleepiness

Area of Science:

• Sleep and Circadian Rhythms
• Thermoregulation
• Human Physiology

Background:

• Skin and core body temperature significantly influence sleep-wake cycles.
• Peripheral cooling may transiently enhance vigilance, particularly in conditions like narcolepsy.
• Understanding the impact of foot cooling on vigilance during extended wakefulness is crucial.

Purpose of the Study:

• To investigate whether foot cooling can maintain vigilance in healthy adults during prolonged wakefulness.
• To test the hypothesis that peripheral cooling influences alertness and sleepiness.

Main Methods:

• Nine healthy young adults participated in a randomized crossover study.
• Participants underwent constant routine trials with mild (30°C), moderate (25°C), or no foot cooling.
• Vigilance was assessed using Psychomotor Vigilance Tasks and drowsiness using Karolinska Drowsiness Tasks.

Main Results:

• Foot cooling did not significantly improve vigilance performance (response speed).
• Subjective sleepiness was transiently reduced by foot cooling.
• Core body temperature declined similarly across all conditions; thermal comfort was unaffected.

Conclusions:

• Mild or moderate foot cooling does not prevent vigilance decline in healthy adults during the typical sleep onset period.
• The observed reduction in sleepiness was minimal and short-lived.
• Foot cooling does not appear to alter core body temperature regulation during extended wakefulness.