Brief Communications

Nature 401, 36-37 (2 September 1999) | doi:10.1038/43366

Physiology: Warm feet promote the rapid onset of sleep

Kurt Kräuchi1, Christian Cajochen1, Esther Werth1 & Anna Wirz-Justice1

Even healthy people occasionally have difficulty falling asleep. Psychological relaxation techniques, hot baths, soothing infusions of plant extracts, melatonin and conventional hypnotics are all invoked in the search for a good night's sleep. Here we show that the degree of dilation of blood vessels in the skin of the hands and feet, which increases heat loss at these extremities, is the best physiological predictor for the rapid onset of sleep. Our findings provide further insight into the thermoregulatory cascade of events that precede the initiation of sleep1.

  1. Chronobiology and Sleep Laboratory, Psychiatric University Clinic, Wilhelm Klein-Strasse 27, 4025 Basel, Switzerland

Correspondence to: Kurt Kräuchi1 e-mail: Email: