The effects of daily bathing and hot footbath (immersion of feet in hot water) in winter on the sleep behavior of nine healthy female volunteers were studied. Subjects were assigned to three sleep conditions: sleep after bathing (Condition B), sleep after hot footbath (Condition F), and sleep without either treatment (Control). Polysomnograms (consisting of electroencephalograph, electrooculograph, and electromyograph) were obtained, and body movements during sleep were measured while monitoring both the rectal and skin temperatures of subjects. In addition, subjective sleep sensations were obtained with a questionnaire answered immediately by the subjects on awakening. The rectal temperature increased by approximately 1.0 degree C under Condition B, but this elevation was not observed under Condition F compared with Control. In contrast, the respective increases in the mean skin temperature of participants subjected to bathing and hot footbath were greater than those of Control, although these temperature differences became negligible 2 h after subjects went to bed. The sleep onset latency was shortened under both conditions compared with Control. Body movements during the first 30 min of sleep in Control were greater than under the other conditions. Rapid eye movement (REM) sleep decreased under Condition B compared with Condition F, and stage 3 was greater under the latter condition compared with Control. As such, the subjective sleep sensations were better under the two treatment conditions. These results suggest that both daily bathing and hot footbath before sleeping facilitates earlier sleep onset. A hot footbath is especially recommendable for the handicapped, elderly, and disabled, who are unable to enjoy regular baths easily and safely.

The aim of this study was to identify the activated brain region that is involved with the affective dimension of thermal stimulation (not pain, but innocuous warming) using functional MR imaging. Twelve healthy, right-handed male subjects participated in the study. Thermal stimulation with two different temperatures of 41 degrees C and 34 degrees C was applied to the subjects using a fomentation pack, wrapped around the right lower leg of each subject. On the basis of the subjects' responses after the scanning sessions, the authors were able to observe that the subjects felt "warm" and "slightly pleasant and comfortable" under the 41 degrees C condition. The experimental results indicated that warm stimulation produced a significant increase of activation compared to thermal neutral stimulation in various regions such as contralateral insular, ipsilateral cerebellum, ipsilateral putamen, contralateral middle frontal gyrus, ipsilateral inferior frontal gyrus, contralateral postcentral gyrus, and contralateral paracentral lobule. The activated regions are known to be related to thermal sensory, affective/emotional awareness, cognitive functions, sensory-discrimination, and emotion/affective processing, and so on. These results suggest that an appropriate thermal stimulation can produce a positive emotion and activate emotion/affect related regions of the brain.

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