Skin temperature changes in paradoxical sleep in man in the cold

Area of Science:

• Physiology
• Sleep Science
• Environmental Medicine

Background:

• Thermoregulation during sleep is crucial for maintaining homeostasis.
• Paradoxical sleep (PS) is associated with significant physiological changes, including altered temperature regulation.
• Understanding skin and core temperature dynamics during sleep in different environments is vital for health.

Purpose of the Study:

• To investigate the relationship between mean skin temperature (Tsk) and rectal temperature (Tre) during different sleep stages, particularly paradoxical sleep (PS).
• To examine how environmental temperature (cold vs. neutral) influences Tsk and Tre during sleep.
• To identify potential critical core temperature thresholds affecting Tsk variations during PS.

Main Methods:

• Continuous monitoring of Tsk (seven sites) and Tre every minute for 88 man-nights.
• Sleep recordings conducted in both cold Arctic winter and neutral laboratory conditions.
• Correlation analysis of temperature data with electroencephalogram (EEG) sleep stages, focusing on PS.

Main Results:

• In a neutral environment, Tre remained above 36°C, and Tsk consistently increased during PS.
• In cold conditions, Tsk increased during PS when Tre was high.
• When Tre dropped below 36°C in the cold, Tsk decreased during PS.

Conclusions:

• The direction of Tsk variation during paradoxical sleep is contingent upon the core body temperature (Tre) at that moment.
• A core temperature of approximately 36°C appears to be a critical threshold influencing Tsk changes during PS.
• Environmental conditions significantly modulate the thermoregulatory responses during sleep.