Effects of mild heat exposure on sleep stages and body temperature in older men.

The purpose of this study was to examine the effects of mild heat exposure on sleep stages and body temperature in older men. Ten healthy male volunteers with a mean age of 69.2 +/- 1.35 years served as subjects. The experiments were carried out under two different sets of conditions: 26 degrees C 50% relative humidity (RH) and 32 degrees C 50% RH. The subjects slept from 2200 hours to 0600 hours with a cotton blanket and wearing short-sleeve pajamas and shorts on a bed covered by a sheet. Electroencephalogram, electro-occulogram and mental electromyogram recordings were made through the night. Rectal and skin temperatures were measured continuously. No significant differences were observed in sleep onset latency. In time spent in each sleep stage, wakefulness was significantly increased at 32 degrees C than at 26 degrees C. The total amount of wakefulness increased and rapid eye movement sleep (REM) decreased at 32 degrees C compared to 26 degrees C. The fall in rectal temperature was significantly suppressed and the mean skin temperature was significantly higher at 32 degrees C than at 26 degrees C. These results suggest that, for older men, even mild heat exposure during the nighttime sleep period may increase thermal load, suppress the decrease of rectal temperature, decrease REM, and increase wakefulness and whole-body sweat loss.

Effects of activity of daily living and gender on circadian rhythms of the elderly in a nursing home.

The objective of this study was to confirm the effects of ADL (Activity of Daily Living) and gender on circadian rhythms of the elderly in a nursing home. Twenty-one elderly volunteers, aged over 65 years, were divided in four groups depending on their ADL and gender: subjects with almost no problem in ADL (H males, H females) and those who were almost bedridden (L males, L females). Oral temperature, heart rate, blood pressure, time of sleep and wake, subjective sleepiness, overall feeling and vitality were measured every 4 hours during the day continuously for six days. The circadian rhythm was calculated by using the least squares fit of cosine function. Subjective sleep quality was also surveyed. In the sleep/wake rhythm, the mesor was significantly higher in L males compared to the other groups and the amplitude was significantly lower in L females compared to other groups. The subjective sleepiness was higher in L males compared to the other groups and L females showed a higher sleepiness compared to H females. No significant difference among the group was observed in subjective sleep quality. In conclusion, these results indicate that the subjective sleepiness and sleep/wake rhythm differ depending on ADL and gender, although no significant difference was observed in physiological parameters. ADL and gender based difference in subjective sleepiness and sleep/wake rhythm should be taken into account with regard to the care of the elderly in nursing homes.

Effects of humid heat exposure on human sleep stages and body temperature.

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.