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Introduction Bathing, especially with hot spring with various mineral compositions, is known to facilitate / improve sleep by warming the body. Artificial carbonated bathing (ACB) is known to keep the body warm too. Previous our study examined that ACB before sleep more specifically affected body temperature and sleep on healthy young subjects. In this study, we evaluated the effects of usual (plain hot water; PH) and artificial carbonated bathing, on sleep using clinical thermometers and EEG in healthy elderly subjects. Methods Nine healthy elderly women (average age 71.3 years old) were divided into 2 groups ACB (858 ppm, Awacomachi, Danrei Co.) and PH with a week interval. Subjects soaked in the bath (38 C degree) deep enough their chests touched the water for 10 min. From the time they finished bathing to the next morning, we measured their distal skin temperature (top side of the foot), proximal skin temperature (lower part of the clavicle) and EEG using a single channel portable device (Brain wave sensor, Proassist Co.). Subjects were told to sleep from 23:00-6:00. As the same time, subjects were examined with visual analog scale (VAS) and clinical flicker fusion test (CFF). Results There was no significant difference in body temperature (proximal, distal, distal-proximal temperature gradient: DPG) before and during sleep between ACB and PH. The condition of the ACB tended to have less light sleep compared to PH (150min vs 201min, p=0.08), but there was no significant difference in the SWS (44.1min vs 39.1min, ns), EEG delta power analysis, VAS and CFF. In the previous study, bathing was performed for 15 min at a water temperature of 40 C degree, but this condition was considered to be a high risk for the elderly. The reason why there was no significant difference in body temperature. The effects of ACB were not fully demonstrated due to changes in hot water temperature and bathing time. Conclusion The effect of ACB on the body temperature of healthy elderly people could not be confirmed. However, a tendency to reduce light sleep was observed. Support This work was supported by JSPS KAKENHI Grant Number JP19K11294