Mild cooling of the feet does not aid night-time vigilance

Ryan Sixtus,James D Cotter,Barbara C Galland

doi:10.1186/2046-7648-4-s1-a114

Ryan Sixtus, James D Cotter + Show 1 more

Open Access

https://doi.org/10.1186/2046-7648-4-s1-a114

Copy DOI

Journal: Extreme Physiology & Medicine	Publication Date: Sep 14, 2015
Citations: 5	License type: cc-by

Affiliation: University of Otago

Abstract

Vigilance is related to core temperature (TC) and skin temperature (Tsk). Biological day reflects a high TC, alertness and modest Tsk; night reflects vice versa [1,2]. At rest, TC is regulated largely via controlling blood flow in extremities (and thus Tsk); vasodilation strongly predicts reduced vigilance [3] and faster sleep onset[4]. In narcolepsy, high daytime extremity temperatures and a smaller distal-to-proximal gradient (DPG) indicates higher sleep propensity [5]. Cool extremities have been linked observationally to delayed sleep onset in the elderly, and experimentally shown to reduce sleep propensity in narcolepsy [6]. Therefore, the aim of this study was to test the hypothesis that cooling the feet would maintain vigilance during extended wakefulness in healthy adults.

Highlights

Vigilance is related to core temperature (TC) and skin temperature (Tsk)
A small and transient reduction in sleepiness was evident with cooling (P = 0.046); otherwise sleepiness and vigilance deteriorated in conjunction with the fall in TC in each condition (r > 0.80)
Participants felt cooler throughout both cooling trials, but thermal comfort was unaffected (P = 0.43), as were almost all EEG parameters during the Karolinska Drowsiness Test (KDT)

Summary

Introduction

Vigilance is related to core temperature (TC) and skin temperature (Tsk). Biological day reflects a high TC, alertness and modest Tsk; night reflects vice versa [1,2]. TC is regulated largely via controlling blood flow in extremities (and Tsk); vasodilation strongly predicts reduced vigilance [3] and faster sleep onset[4]. High daytime extremity temperatures and a smaller distal-to-proximal gradient (DPG) indicates higher sleep propensity [5]. Cool extremities have been linked observationally to delayed sleep onset in the elderly, and experimentally shown to reduce sleep propensity in narcolepsy [6]. The aim of this study was to test the hypothesis that cooling the feet would maintain vigilance during extended wakefulness in healthy adults

Objectives

Methods

Results

Discussion

Conclusion