The thermophysiological cascade leading to sleep initiation in relation to phase of entrainment

Women with vasospastic syndrome exhibit a prolonged sleep onset latency (SOL).

• Circadian thermoregulation is linked to sleep induction and the timing of the sleep-wake cycle.
• Mammals typically sleep during the lowest point of their core body temperature (CBT) rhythm.
• Sleep onset is influenced by body heat loss, which occurs maximally during the decline of the CBT curve.
• Selective widening of blood vessels in the skin promotes sleepiness prior to sleep onset.
• Women with vasospastic syndrome show reduced heat loss during the day and experience disrupted timing of their circadian clock.
• The regulation of blood flow to the skin may be relevant for understanding and treating sleep onset insomnia.

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