Briefly exposing yourself to intense cold right before bedtime helps induce rapid sleep onset and improves sleep quality by lowering your core body temperature.

noli's read

The scientific community strongly agrees that cooling the body is a powerful lever for sleep. Science confirms that a drop in core body temperature is an essential biological signal to initiate sleep (study published in Nature, observational/experimental). The use of cooling devices (cooling mattresses) has effectively shown positive results on sleep onset latency in people suffering from insomnia (RCT, research on cranial cooling systems). However, direct exposure to intense cold outdoors before bedtime is an anecdotal practice: while thermal shock can promote a feeling of drowsiness through a rebound effect, it carries significant risks (hypothermia, cardiovascular stress). The idea that this neutralizes external noise is likely more related to a state of extreme fatigue or sensory focus than to a proven biological mechanism. It is therefore accurate to say that cooling promotes sleep, but the extreme approach described remains a personal interpretation that has not been clinically validated.

the sources

1. 1r/Biohackers