Warm ears, a red flag for sleepiness?

Journal of Sleep Research, vol. 32, pp. e13707

Abstract

Summary Core body and skin temperatures are intimately linked to sleep and alertness. The distal‐to‐proximal skin temperature gradient has been described as a good physiological predictor for sleep onset. Increased ear skin temperature is often caused by increased blood flow reflected in redness, which is commonly noticed in people who are sleepy, especially anecdotally in children. Nonetheless, no prior study investigated the possible relation between sleepiness and ear skin temperature as a separate measurement. We assessed the relation between ear skin temperature and sleepiness in patients undergoing regular electroencephalographic examinations, because of suspicion of epilepsy, both without and after sleep deprivation. Subjective sleepiness was measured using the Stanford Sleepiness Scale, and objective sleepiness by determining sleep onset with electroencephalography. Distal, proximal and ear skin temperature were measured repeatedly using wireless measurement devices (iButtons). Forty‐four adult patients were included. Ear skin temperature correlates weakly with distal skin temperature (r = 0.174, p < 0.001) and distal‐to‐proximal gradient (r = 0.160, p < 0.001), but not with proximal skin temperature (r = −0.001, p = 0.975). Ear skin temperature increased significantly in a subgroup of 13 patients, between 5 and 1 min before sleep onset (p = 0.002; η2 = 0.059), even though this increase was also associated with supine posture. iButtons is a valid method to measure ear skin temperature, which appears to function partly like a distal and partly like a proximal skin temperature measurement. Change in ear skin temperature is associated with sleep onset and supine posture.

Authors 6

1. Mink Sebastian Schinkelshoek corresponding Aachen Department of Neurology Leiden University Medical Center Leiden the Netherlands Department of Neurology, Leiden University Medical Center (LUMC)

   Leiden University Medical Center · Stichting Epilepsie Instellingen Nederland

   Affiliation as printed

   Department of Neurology Leiden University Medical Center Leiden The Netherlands

   Sleep‐Wake Center Stichting Epilepsie Instellingen Nederland (SEIN) Heemstede The Netherlands

   Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands

   Sleep-Wake Center, Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands

2. Rolf Fronczek Aachen Department of Neurology Leiden University Medical Center Leiden the Netherlands Department of Neurology, Leiden University Medical Center (LUMC)

   Leiden University Medical Center · Stichting Epilepsie Instellingen Nederland

   Affiliation as printed

   Department of Neurology Leiden University Medical Center Leiden The Netherlands

   Sleep‐Wake Center Stichting Epilepsie Instellingen Nederland (SEIN) Heemstede The Netherlands

   Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands

   Sleep-Wake Center, Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands

3. Anke F. J. de Boer Aachen Department of Neurology Leiden University Medical Center Leiden the Netherlands Department of Neurology, Leiden University Medical Center (LUMC)

   Leiden University Medical Center

   Affiliation as printed

   Department of Neurology Leiden University Medical Center Leiden The Netherlands

   Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands

4. Kay de Wit Aachen Department of Neurology Leiden University Medical Center Leiden the Netherlands Department of Neurology, Leiden University Medical Center (LUMC)

   Leiden University Medical Center

   Affiliation as printed

   Department of Neurology Leiden University Medical Center Leiden The Netherlands

   Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands

5. Martijn Rudolf Tannemaat Aachen Department of Neurology Leiden University Medical Center Leiden the Netherlands Department of Neurology, Leiden University Medical Center (LUMC)

   Leiden University Medical Center

   Affiliation as printed

   Department of Neurology Leiden University Medical Center Leiden The Netherlands

   Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands

6. Gert Jan Lammers Aachen Department of Neurology Leiden University Medical Center Leiden the Netherlands Department of Neurology, Leiden University Medical Center (LUMC)

   Leiden University Medical Center · Stichting Epilepsie Instellingen Nederland

   Affiliation as printed

   Department of Neurology Leiden University Medical Center Leiden The Netherlands

   Sleep‐Wake Center Stichting Epilepsie Instellingen Nederland (SEIN) Heemstede The Netherlands

   Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands

   Sleep-Wake Center, Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands