BrainSleep Co., Ltd. (Head office: Chiyoda-ku, Tokyo; Representative Director: Atsushi Hirota; hereinafter "BrainSleep") collaborated with Super Hotel Co., Ltd. (Head office: Osaka-shi, Osaka; President: Kensaku Yamamoto; hereinafter "Super Hotel") and Associate Professor Sachiko Uemura of Akita University Graduate School of Medicine (hereinafter "Akita University") to verify the sleep-inducing effects of natural hot springs installed in hotels.The results of the verification showed that bathing in natural hot springs promotes an efficient decrease in core body temperature, leading to improved sleep onset. Background of the Initiative For many hotel guests, "sleep" is the longest period of their stay. However, a hotel is a different environment from home, and sleep tends to be disturbed, such as by light sleep, due to differences in sound, light, temperature, bedding, and so on. Super Hotel established the "Gussuri Lab" (Sound Sleep Lab) based on the philosophy of helping customers sleep "soundly" and start the next day refreshed and in perfect condition, and has been engaged in sleep-focused initiatives. At the request of Super Hotel, we collaborated with Associate Professor Sachiko Uemura of Akita University, who is a leading researcher on the effects of hot springs on sleep, to verify whether hotel natural hot springs are effective for sleep.The results of this verification demonstrate the effects of natural hot springs on sleep and are expected to be one solution to sleep problems. Verification Overview In this verification, the effects of natural hot springs within hotels on sleep were evaluated using the following method:Verification period: November to December 2024Number of subjects: 18 individuals aged 20-60 (11 of whom were female)Location: Yumoto "Hananoi" Super Hotel Osaka Natural Hot SpringsVerification method: A crossover study was conducted where subjects participated in three conditions for three days each: "natural hot spring condition (bathing in the hotel's natural hot spring before bedtime)", "room bath condition (bathing in the guest room's bath*1 before bedtime)", and "morning shower condition (showering after waking up)".Measurement items: Electroencephalogram, activity level, core body temperature, questionnaire evaluation (OSA Sleep Questionnaire)*2 *1 The temperature of the natural hot spring was adjusted to 40°C, and bathing time was unified with the natural hot spring condition.*2 A general sleep evaluation method advocated by the Japanese Association for Sleep Improvement, which statistically quantifies subjective sleep feelings. Verification Results The results below confirmed that on nights when subjects bathed in natural hot springs before bed, they fell asleep more easily and had a higher evaluation of their sleep. This is thought to be due to the natural hot springs efficiently raising core body temperature, which then smoothly decreased at bedtime. Result ①: Objective data from electroencephalogram Analysis of electroencephalogram data confirmed that sleep latency (the time it takes to fall asleep after getting into bed) was significantly shorter under the natural hot spring condition. This objective data indicates that subjects fell asleep faster on nights when they bathed in the natural hot spring. Result ②: Subjective data from questionnaires Subjective evaluations of sleep were compared using the OSA Sleep Questionnaire, a psychological scale for evaluating one's sleep upon waking. Among the five sleep factors, the natural hot spring condition showed significantly higher scores for the following four sleep factors. This indicates that on nights when subjects bathed in a natural hot spring, they fell asleep more easily, had more stable sleep, and reported feeling refreshed upon waking.I. Sleepiness upon waking: How clear one's consciousness is, including concentration and sense of openness.II. Sleep onset and maintenance: Whether one fell asleep easily and slept stably without waking during the night.IV. Fatigue recovery: Whether one felt refreshed and recovered from fatigue.V. Sleep duration: Whether one felt they had sufficient sleep. Result ③: Objective data from core body temperature Core body temperature, the temperature inside the body, rises during the day and falls at night according to the body's internal clock. For good quality sleep, it is important to lower this core body temperature appropriately. When core body temperature temporarily rises due to external factors, it tends to decrease more easily afterward due to thermoregulation. Therefore, bathing before bedtime is said to promote a decrease in core body temperature, making it easier to fall asleep*3.In this study, the difference between the maximum and minimum core body temperature was used as an indicator, with a larger value indicating a greater decrease in core body temperature. The results confirmed that the difference between the maximum and minimum temperature was significantly larger under the natural hot spring condition, indicating a more efficient decrease in core body temperature. ※3 Source: Seiji Nishino, "Stanford University's Best Sleep Method" (Sunmark Publishing) Comment from Akita University Associate Professor Sachiko Uemura When you're more tired than usual from business trips or travel, there's nothing better than a hot spring bath to rest and refresh your body. Japanese people love hot springs, so much so that there's even a word for "hot spring cure" (toji). Hot springs are known to improve blood circulation and have pain-relieving effects, in addition to promoting sleep. The reason for this is that many hot springs have a strong heating effect, causing core body temperature to rise more than in a home bath. Since the human body controls itself to prevent core body temperature from rising too high, it tries to rapidly lower a rapidly elevated core body temperature. It is known that at this time, people experience strong drowsiness. Furthermore, it is known that core body temperature then falls lower than usual late at night, which is known to provide a feeling of deep sleep. This study of Super Hotel's natural hot springs also demonstrated a rapid fluctuation in core body temperature and the resulting ease of falling asleep. I would definitely like to use them when I travel for business. Sachiko Uemura Associate Professor, Department of Physical Therapy, Graduate School of Medicine, Akita University Comment from BrainSleep Chief Research Advisor Seiji Nishino I have been researching the effects of bathing and hot spring bathing on sleep with Professor Uemura of Akita University for some time. We know that when you take a bath, your core body temperature temporarily rises, and then you can get a deep sleep by going to bed during the subsequent cooling period. Furthermore, a comparison between hot springs and regular bathing revealed that hot spring bathing caused a more significant rise in core body temperature and subsequent drop at bedtime, even under the same conditions (same temperature and bathing time as regular bathing), leading to deeper sleep. Super Hotel has natural hot springs, and guests staying at Super Hotel can easily enjoy hot spring bathing at their leisure. For this reason, we verified the effects of hot springs on sleep under Super Hotel's accommodation conditions. Similar to the results of previous research, natural hot spring bathing led to faster sleep onset and higher quality deep sleep compared to showering or bathing in a room bath. The next morning, there was less sleepiness, a feeling of fatigue recovery, and well-rested sleep. The fact that optimal sleep was achieved with Super Hotel's natural hot spring bathing is thought to be due to the hot spring's ingredients efficiently absorbing heat into the body, raising core body temperature, and causing it to drop significantly. Super Hotel is the optimal choice for recovering from fatigue caused by work or sightseeing. Seiji NishinoProfessor, Department of Psychiatry, Stanford University School of Medicine; Director, Stanford University Sleep and Circadian Neurobiology LaboratoryFounder and Chief Research Advisor, BrainSleep Co., Ltd.Physician, Doctor of Medical ScienceCertified Qualifications: Designated Physician for Mental Health, Japanese Society of Sleep Research Certified Specialist, Industrial Physician Joint Verification Partner Super Hotel Co., Ltd. Established: December 1989 Location: 1-7-7 Nishihonmachi, Nishi-ku, Osaka-shi, Osaka Representative Director: Kensaku Yamamoto Official Website: https://www.superhotel.co.jp/ Akita University Location: 1-1-1 Hondo, Akita-shi, Akita Lead Researcher for this Verification: Sachiko Uemura Affiliation: Department of Physical Therapy, Graduate School of Medicine, Akita University Title: Associate Professor
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