The thermophysiological cascade leading to sleep initiation in relation to phase of entrainment.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing theoretical concepts and previously published studies with no new empirical dataset or systematic review methodology.
PubMed 17764994 · doi:10.1016/j.smrv.2007.07.001
What was done
This paper reviews circadian thermoregulatory mechanisms and chronobiological models (specifically referencing concepts from Jürgen Aschoff) governing sleep induction and phase of entrainment. It also examines clinical and physiological observations from studies involving individuals with vasospastic syndrome (characterized by cold hands and feet, primarily in women) as a model for impaired distal thermoregulation.
What was found
The abstract reports no numerical data or statistical effect sizes. It describes that sleep initiation coincides with the declining slope of the core body temperature curve, driven by maximal distal skin vasodilation and body heat loss prior to lights-off. In women with vasospastic syndrome, impaired daytime heat loss corresponds to prolonged sleep onset latency, altered phase of entrainment between the circadian clock and sleep-wake cycle, and inward-directed anger.
Why it matters
It outlines how distal vasodilation directly couples circadian temperature regulation to sleepiness, presenting distal skin blood flow as a physiological target for understanding and treating sleep onset insomnia.
Limits
As a narrative review, it lacks systematic search criteria, meta-analytic pooling, and quantitative data in the abstract. Evidence derived from vasospastic syndrome represents a selective clinical subgroup (predominantly women), limiting direct generalizability to all forms of insomnia or the broader population.
Cited by
- supports In order to fall asleep and stay deeply asleep, human core body temperature must decrease by approximately 1 to 3 degrees Fahrenheit.
- supports In order to fall asleep and stay deeply asleep, human body temperature must decrease by approximately 1 to 3 degrees.