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. 2023 Sep 8;42(1):20.
doi: 10.1186/s40101-023-00337-0.

Effects of bathing-induced changes in body temperature on sleep

Takafumi Maeda  1   2 , Hiroko Koga  3 , Takashi Nonaka  3 , Shigekazu Higuchi  4   5
Affiliations

Effects of bathing-induced changes in body temperature on sleep

Takafumi Maeda et al. J Physiol Anthropol. .

Abstract

Background: Passive body heating before sleep is well known to lead to improved sleep. However, the effects of the degree of change in body temperature by bathing on sleep quality are unclear. The present study aimed to clarify the effects on sleep of bathing-induced changes in body temperature.

Methods: Twenty-three healthy males and females in their 20 s to 50 s bathed in their homes 1.5-2 h before bedtime under three bathing conditions: showering only; short bathing in a bathtub; and long bathing in a bathtub. Sublingual and skin temperatures and thermal sensation before and after bathing, sleep indices such as sleep onset latency, time in bed, sleep efficiency, and wake after sleep onset, all of which were evaluated using an actimeter, and subjective evaluations of sleep were compared among conditions.

Results: Sublingual temperature just after bathing was significantly higher with long bathing than with other conditions, and the fall in sublingual temperature from after bathing to before sleep was significantly larger with long bathing than with short bathing. Sleep onset latency by actimeter was significantly reduced with long bathing compared to showering. In addition, subjective evaluations of falling asleep and sleep quality were better with long bathing than with showering or short bathing.

Conclusions: In conclusion, bathing conditions that produce a 0.9 °C increase in sublingual temperature appear effective for falling asleep and sleep quality, because core temperature shows a greater drop to before sleep than those producing an increase of about 0.3 °C increase in sublingual temperature.

Keywords: Bathing; Body temperature; Distal-to-proximal skin temperature gradient; Sleep onset latency; Sleep quality.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Sleep parameters assessed using the actimeter. a Sleep onset latency; b time in bed; c sleep efficiency; and d wake after sleep onset. *Significant difference, p < 0.05
Fig. 2
Fig. 2
Subjective feeling of falling asleep and quality of sleep. Squares, triangles, and circles indicate showering and short and long bathing conditions, respectively. ** Significant difference from showering condition, p < 0.01. # Significant difference from short bathing condition, p < 0.05. ## Significant difference from short bathing condition, p < 0.01
Fig. 3
Fig. 3
OSA-MA score. a Five factors of OSA-MA. b Contents in Factor II (initiation and maintenance of sleep). OSA-MA, Oguri–Shirakawa–Azumi Sleep Inventory, Middle-aged and Aged version. Grey, orange, and red marks indicate showering and short and long bathing conditions, respectively. *Significant difference, p < 0.05. **Significant difference, p < 0.01
Fig. 4
Fig. 4
Thermal sensations for the whole body, back of the hand, and feet before going to sleep. Squares, triangles, and circles indicate showering and short and long bathing conditions, respectively. *Significant difference from showering condition, p < 0.05
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