Red Ears while sleepy: assessment of the relation between ear temperature and sleepiness in patients undergoing EEG examination

Core body and skin temperature are intimately linked to sleep and alertness.
The combination of a relatively high core body temperature and a relatively low
skin temperature is associated with wakefulness [1], while the opposite pattern
is associated with sleep. The change from a diurnal to a nocturnal pattern is
mediated through increased perfusion of the distal skin (i.e. hands and feet),
facilitating cooling of the body [2]. Interestingly, vice versa, a high distal
relative to proximal skin temperature facilitates the transition from wake to
sleep [3].

There are well-known anecdotes about the relation between red ears and
sleepiness, especially in children. To delve deeper into this possible
relationship, we plan to measure ear temperature in adults undergoing an EEG
examination at the outpatient clinic of the Department of Clinical
Neurophysiology of the Leiden University Medical Center. Patients undergoing
such an EEG registration are of interest, because part of these registrations
will be performed after obligatory sleep deprivation to increase the chance of
finding epileptiform discharges. These patients will thus be sleepy, and they
can be compared to patients that are not sleep-deprived (not sleepy).
Furthermore, whether patients actually fall asleep during the registration and
the subsequent sleep latency, are other parameters of interest that can be
related to the presence of red ears.

To assess whether a higher ear temperature is related to objective and
subjective sleepiness, and subsequent sleep onset in patients undergoing a
standard EEG examination. A secondary objective is to investigate whether ear
temperature is related to distal and/or proximal skin temperature.

Patients will be divided in two group: a sleep deprived group (the decision to
sleep deprive this group is completely based on clinical reasons and is not
influenced by this study) and a non-sleep deprived control group, both
undergoing a standard EEG examination. Ear temperature will be assessed by
thermographic camera imaging prior to and after EEG examination. Distal and
proximal skin temperature will be measured frequently using iButtons. Objective
sleepiness will be assessed by sleep-onset latency and subjective sleepiness by
a validated questionnaire (Stanford Sleepiness Scale).

The assessments are of negligible burden and without risk. Transportation costs
will not be compensated, since no additional transportation is needed for
participating in this study. The duration of the entire experiment will
approximately take 15 minutes in addition to the duration of the EEG
examination.