title: Effects of humid heat exposure on human sleep stages and body temperature.
abstract: The objective of this study was to confirm the effect of humid heat exposure on sleep stages and body temperature. Seven healthy male volunteers with a mean age of 22.7+/-1.63, served as the subjects. The experiments were carried out under four different conditions of room temperature and relative humidity: 29 degrees C RH 50% (29/50), 29 degrees C RH 75% (29/75), 35 degrees C RH 50% (35/50), and 35 degrees C RH 75% (35/75). The subjects wearing only shorts slept from 23:00 to 7:00 on a bed, which was covered with a 100% cotton sheet. EEG, EOG, and mental EMG were recorded through the night. Rectal temperature (Tr) and skin temperature were measured continuously. The 35/75 condition caused more wake and a lower sleep efficiency index (SEI) and stage S3+S4 than 29/50 and 29/75. Stage REM and stage 3 were significantly decreased at 35/75 than at 29/50 and 35/50. Tr was maintained at a higher level at 35/75 than under the other conditions. Mean skin temperature was higher at 35/50 and 35/75 than at 29/50 and 29/75. These results suggest that humid heat exposure during night sleep increases the thermal load to supress the sleep-evoked Tr decrease, stage 3, SWS, and REM, and increase wakefulness.
authors.affiliation: Department of Physiology, Dokkyo University School of Medicine, Shimotuga, Tochigi. okamoto@dokkyomed.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Okamoto-Mizuno
authors.forename: K
authors.initials: K
authors.lastname: Mizuno
authors.forename: S
authors.initials: S
authors.lastname: Michie
authors.forename: A
authors.initials: A
authors.lastname: Maeda
authors.forename: S
authors.initials: S
authors.lastname: Iizuka
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D004585:Electrooculography; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D006813:Humidity / Q000009:adverse effects*; D008297:Male; D012894:Sleep Stages / Q000502:physiology*; D013546:Sweating / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology