The primary objective of this study was to collect evidence that individuals who use hot spring facilities and public baths have a low risk of being infected with COVID-19. The secondary objective was to comprehensively summarize the research issues that remain to be explored in the field of balneology considering results of previous research.

  Literature databases used were CINHAL, Cochrane Library (Clinical Answer, Cochrane Protocol, Cochrane Review, Editorials, Special Collections, Trials), Ichushi Web (in Japanese), MEDLINE, and Web of Science Core Collection. For each database, we selected results from the time it was opened through July 26, 2021. When intervention studies and experimental were searched, the following modified PICOS was used the following: P (Participant: no restrictions on the presence or absence of illness), I (Intervention: normal breathing or intentional sneezing, coughing, conversation), C (Comparison: no restrictions), O (Outcome: markers that simulate the flow of indoor air, the dynamics of droplets, and droplets in bathrooms and dressing rooms), and S (Study design: including intervention studies and experiments without a control group). For observational studies, PECOS included: P (participants: unlimited with or without disease), E (Exposure: public bathing facility), C (comparison: unrestricted), and S (study design: cross-sectional study, cohort study, and case-control study).

  For the primary objective, no studies met the eligibility criteria, and at the time of this study there was no evidence that the use of hot spring facilities or public baths presented a low risk of being infected with COVID-19. Regarding the secondary objective, there were 15 relevant studies. In the context of a society that is strongly influenced by COVID-19, our literature review identified four research issues: “A. Use of hot spring facilities and public baths has a low risk of COVID-19 infection”, “B. The quality of hot springs and the room temperature and water temperature of public baths make SARS-CoV-2 inactivate/attenuate”, “C. Hot spring facilities, public baths, bathing habits at home lead to prevention of COVID-19 and alleviation of symptoms”, “D. Bathing for survivors of COVID-19 is effective for various rehabilitation of patients”. Suitable research approaches for each issue would be required in order to grasp each evidence.

  Background: Heat shock proteins (Hsps), expression of which are induced by thermal treatment, function in the protection of kidneys by suppressing apoptosis and maintaining renal tubular viability. Moreover, recently, it has been indicated that the expression of Hsps can be a therapeutic target for autosomal dominant polycystic kidney disease (ADPKD). We investigated the effect of dry sauna therapy on ADPKD model mice.

  Methods and Results: The mice (male DBA/2FG-pcy mice) were categorized into three groups: controls, TS: pcy mice subjected to prolonged sauna with administered water containing 4% sucrose, SW: pcy mice administered water containing 4% sucrose. The TS group was subjected to sauna sessions twice a week for four weeks. The TS group attained and were maintained at rectal temperatures of approximately 39.0°C, until they were carefully removed from the far infrared-ray device. After 4 weeks of sauna treatment, creatinine and blood-urea-nitrogen (BUN) levels determined by an enzymatic method. The heat shock protein (HSP) or cell growth and size related proteins were analyzed by western blotting. The TS group exhibited marginally higher creatinine and BUN levels than did the control and SW groups, however, the differences were not significant. However, cyst enlargement in the TS group reduced significantly compared to that of the control group. HSP90 expression was slightly decreased in the TS and SW groups relative to the control group (p < 0.01 or p < 0.001, vs. control), as was Erk expression, which is linked to cyst development and proliferation (p < 0.05, TS vs. control). Hsp27 expression and phosphorylation level in the SW group were comparable with that of the control group. However, the TS group had increased levels of Hsp27 and phosphorylation (NS). The expression of pro-caspase-3 in the TS group was marginally lower than that in the control group. However, the activity of caspase-3 in all groups showed no differences.

  Conclusion: The findings of this study indicated that 4 weeks of sauna treatment could cause transient dehydration and related renal dysfunction and led to the risk of stimulating cyst growth by increased Hsp27 expression. Moreover, we concluded that prevention of dehydration and cyst growth could be suppressed by taking an appropriate amount of water directly after sauna treatment.

  Background: Aging affects thermoregulation and can potentially cause cardiovascular changes during bathing in the elderly, possibly leading to accidents and, in worst cases, drowning. However, adequate data on this subject are lacking. Therefore, the purpose of this study was to clarify the effect of aging on thermoregulatory and cardiovascular changes during bathing in the older versus younger adults the relationship between body temperature and thermoregulatory and cardiovascular changes.

  Methods: Ten young (mean age: 20.4 years) and 10 elderly (mean age: 69.7 years) participants were asked to bathe for 15 min using water at 41°C. Tympanic temperature (Tty), skin blood flow (SkBF), sweating rate (SR), blood pressure, heart rate (HR), and double product (DP) were measured. In addition, we measured subjective psychological changes during bathing. Results: The results showed significant changes in SkBF, SR, and HR in the young participants rather than in the elderly participants. However, in the elderly participants, significant change was noted in systolic blood pressure (SBP).

  Conclusion: These results demonstrate changes in thermal adaptation and SBP owing to structural and functional progression due to aging.

  Objective: We investigated the effects of 5 days of spa therapy on the glycation reaction and oxidative balance defense system.

  Subjects: The subjects were divided into a glucose spikes group (S group: 5 cases) and non-glucose spike group (non-S group: 6 cases), and a comparative study was conducted.

  Method: The subjects stayed at the Inubosaki Onsen “Superb View Inubosaki Hotel” for 5 days and took spa baths twice a day for 20 min (balneotherapy). Before and after the baths, the degree of glycation was measured. Erythrocyte deformation by dark field microscope was classified into stages between 0 and 5, and the state of deformation and the levels of advanced glycation end products (AGEs) were measured. In addition, the oxidative stress (reactive oxygen metabolites, d-ROM), antioxidant power (biological antioxidant potential, BAP), and latent antioxidant capacity (BAP/d-ROM ratio) were also measured.

  Result: The red blood cell images before balneotherapy were worse in the S group, but there was no significant difference in the AGE values. There was also no significant difference between the two groups in terms of the oxidative balance defense system. A comparison before and after balneotherapy showed that the red blood cell images significantly improved from 3 (3-3) (median (IQR)) to 2 (1-2)°in the S group. Oxidative stress also significantly improved in group S from 342 (334-362) to 314 (303-345) CARR U. In the non-S group, the AGE value improved significantly from 0.52 (0.48-0.59) to 0.5 (0.43-053) a.u. There were no significant differences in the other items.

  Discussion: Changes in red blood cell images are considered to reflect changes in the early reactions of glycation, and AGEs may be evaluated as representing whole early and late reactions of glycation. In the S group, the early reaction improved, and in the non-S group, the entire glycative reaction was effective. Although the each mechanism of blood glucose to different, balneotherapy was shown to be effective in improving glycation.

  This center was established at its downtown in 2011. In order to either maintain or promote health-welfare status at the elderly life stage, the center has been providing regular physical exercise courses using hot spring water pumped up there. These activities have been performed cooperating with all 32 community general support centers covered whole the city.

  Main findings and indication from our activities in these10 years were as follows:

  1．Total number of attendants increased from around 60 to 90 thousands a year. About one fourth of them were the QOL (Quality of Life) tour member aged 65 years or more attending twice a week in every 3-month by the courtesy bus, and the others aged 40 years or more attended with their own ways.

  The attendants aged 75 years or more has gradually increased to 70〜80% of QOL tour member. For the other member, it has been in 20〜30% these 10 years.

  In addition to the physical exercise in 33〜36°C hot spring water consisted of walking, stretch & flex, aquatic exercise for joint-musculoskeletal pain and others, power-up rehabilitation, exercise for joint-musculoskeletal pain and others were performed on floor, too. The grade of these exercise consisted of 30, 40 and 50% of maximum heart rates depending on physical examination results of 5 m-walk, timed up & go test (TUG), the 30 seconds chair-stand test (CS30), hand grip, functional reach and posture forward bending, and doctors’ inspection.

  2．On the follow-up of the physical examinations measured every 3-month, 5 m-walk, hand grip and CS30 were shown to be suitable items due to the availability as the routine examination. The results are substantially useful for reviewing each attendant status in longitudinal course, and indicate our treatments for them.

  3．The attendants increased and distributed over the whole city in these 10 years. However, as the proportion of new ones is several percentages each year, the exchange of attendants was less than we expected. This indicates that we should have closer communication with community general support centers in order to distribute our activities to people who need health-welfare promotion, but have never been in the center. On top of that, the usage of our center should be increased for people of middle ages for ideal prevention.

  The author has researched and reported on “Efforts to increase the demand for long-term stays in spa resorts” over three reports up until now. The target areas were spa health resorts and national park resort villages with spas. There, I pointed out the necessity to create programs for stays that combine the natural environments, historical and cultural environments, artificial environments and facilities, different environments by moving around and night-time hours that exist around each stay facility.

  In this repot, I investigated the creation of programs for public Kokumin Shukusha, which are dormitories for the people who can stay with peace of mind, even with their families, at a low cost. I investigated whether or not efforts are being made to create programs for staying, such as setting walking trails that make use of external environments around the public Kokumin Shukusha.

  As a result, although efforts were made, the number and diversity of course settings were insufficient. In order to increase the demand for long-term stays, it will be necessary to utilize the external environment that make the most of the nearness to existing villages. In addition, it became clear that the Onsen Stay policy promoted by the Ministry of the Environment has not been publicized, and it is necessary to promote the publicity of this policy in order to revitalize spa resorts nationwide.