In healthy people, both sleepiness and vigilance show a relationship with core body temperature and skin temperature.
When core body temperature is high during the daytime, skin temperature is low, which translates into optimal vigilance. Conversely, when core body temperature is low at night time, skin temperature is high, which correlates to optimal sleep. Among those suffering from narcolepsy, however, direct manipulations of their skin and core body temperatures affect their vigilance and sleepiness, according to a study published in the February 1 issue of the journal SLEEP.
The study, authored by Rolf Fronczek, of the Netherlands Institute for Neuroscience in Amsterdam, and Leiden University Medical Center in The Netherlands, focused on eight patients who were diagnosed with narcolepsy with cataplexy and suffered from excessive daytime sleepiness. The subjects' vigilance was measured using the Psychomotor Vigilance Task, and their sleepiness was assessed with the Maintenance of Wakefulness Test. Meanwhile, their skin temperature was mildly manipulated using a thermosuit, while their core body temperature was manipulated using hot or cold food and drinks.
According to the results, patients were better able to maintain vigilance when core body temperature was increased than when it was lowered, indicating that vigilance in narcolepsy can be altered simply by altering the temperature of food and drinks. Also, the ability to maintain wakefulness was better when skin temperature was lowered than when it was increased. Therefore, the process of falling asleep in narcoleptic subjects was able to be influenced by gently cooling or warming their hands and feet.