Health Effects of Seasonal Bathing in Hot Water, Seasonal Utilization of Hot Spring Facilities, and High Green Tea Consumption

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1 J Jpn Soc Balneol Climatol Phys Med (2014) 77 (2) 171 Health Effects of Seasonal Bathing in Hot Water, Seasonal Utilization of Hot Spring Facilities, and High Green Tea Consumption Yasuaki GOTO 1),3), Shinya HAYASAKA 1),2), Yoshikazu NAKAMURA 3) Abstract Among lots of lifestyle factors thought to be related to the Japanese health status, bathing in hot water, utilizing onsen (hot spring) facilities, and drinking green tea are very special among the Japanese. In our previous study, we investigated the frequency of bathing, the utilization of onsen facilities, and the consumption of green tea among the Japanese and found that these activities improved subjective health to a similar degree as balanced diet, exercise, no tobacco use, and quality sleep. In the present study, to ascertain healthy activities that should be encouraged throughout the year, we included survey items about seasonal variations in taking baths, taking showers, and utilizing onsen facilities, as well as investigated the difference between consumption of brewed green tea and of canned and bottled green tea. A crosssectional questionnaire survey was conducted of 6,000 residents in Shizuoka prefecture aged B20 years in Using unconditional logistic models, odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated for several factors that were considered to affect selfrated health (SRH; subjective health, sufficient sleep and rest, and subjective happiness). This time, in a more detailed investigation of bathing habits, onsen utilization, and green tea consumption, we found that daily bathing all year round (subjective health: OR=1.27, 95%CI ; p=0.012, sufficient sleep and rest: OR=1.41, 95%CI ; p=0.003, subjective happiness: OR=1.35, 95%CI= ; p<0.001), utilization of onsen facilities (subjective happiness: OR=1.25, 95%CI = ; p = 0.021), and daily consumption of at least 500 ml of brewed green tea (subjective health: OR=1.24, 95%CI ; p=0.039) are health-improving habits that should be proactively encouraged in daily living. We believe that the inclusion of a formal recommendation for daily green tea consumption and daily bathing and the establishment of reference values for these habits in the Health Promotion Policy will foster health and longevity in Japanese citizens. Key words: Bathing, Onsen (Hot spring), Green tea, Self-rated health, Lifestyle habit (Received: November 19, 2013, Accepted: January 31, 2014) 1) ONSEN Medical Science Research Center, Japan Health & Research Institute 2) Faculty of Sports and Health Science, Department of Health Science, Daito Bunka University 560 Iwadono, Higashimatsuyama, Saitama , Japan TEL: , FAX: ) Department of Public Health, Jichi Medical University

2 172 Y. GOTO et al. I INTRODUCTION The Japanese have long life expectancy. As Breslow et al. pointed out, a healthy lifestyle contributes to longevity 1), and one of the key factors regarding the long lifespan of the Japanese is the traditional diet 2). The present study focuses on characteristics of the Japanese lifestyle other than traditional foods and investigates the effects of bathing in hot water, utilizing hot spring ( onsen in Japanese) facilities, and drinking large amounts of green tea. From a global perspective, the Japanese bathing style is unique in that the daily bathing routine involves soaking in hot water heated to approximately 40 3),4). Typical Japanese bathrooms contain both a bathtub and a space for washing the body. Because of this unique design, hot water in the bathtub can be kept clean and used by several people, for example, an entire family. To the Japanese, the main purpose of bathing is not only to clean and wash the body, but also to warm it in the bathtub. Although bathing has many positive effects, the most beneficial is the thermal effect which improves blood flow via the dilation of blood vessels 5),6), thereby reducing CO 2 and increasing O 2 levels in the extremities. In this way, bathing can refresh the body after a day of work. Japan is a volcanic country that possesses 7% of the world s active volcanoes. Consequently, there are over 3,000 onsen resorts and 27,000 natural springs throughout the country. Onsen visits are a popular leisure activity in Japan, and the utilization of onsen facilities has been shown to reduce mortality rates of stroke, cardiovascular disease, and bone fracture among the elderly 7). Japanese lifestyle is also characterized by a large consumption of green tea 8), a beverage that can reduce the mortality associated with cardiovascular disease 9). In addition, green tea contains catechin, caffeine, theanine, and vitamin C, which benefit mental and physical health 10). We previously investigated the frequency of bathing, the utilization of onsen facilities, and the consumption of green tea among the Japanese and found that these activities improved subjective health to a similar degree as balanced diet, exercise, no tobacco use, and quality sleep 11). In the present study, to ascertain healthy activities that should be encouraged throughout the year, we included survey items about seasonal variations in taking baths, taking showers, and utilizing onsen facilities, as well as investigated the difference between consumption of brewed green tea and of canned and bottled green tea. II MATERIAL AND METHODS 1. Design Between November 20 and December 14, 2012, we conducted a cross-sectional questionnaire survey of 6,000 residents of Shizuoka Prefecture (men and women, 3,000 each; age, B20 years) who had been selected by two-stage stratified random sampling based on a voter registration list. 2. Measures Survey items were sex, age, annual income, self-rated health (SRH; subjective health, sufficient

3 Contribution of Seasonal Bathig, Onsen and Green Tea to Good Health Status 173 sleep and rest, and subjective happiness), frequency of baths per week (all year round, in summer, in spring or fall, and in winter), frequency of showers per week (all year round, in summer, in spring or fall, and in winter), frequency of onsen visits per month (all year, in summer, in spring or fall, and in winter), and amount of green tea consumption per day (from tea leaves, cans, and plastic bottles). 3. Analysis method A logistic regression analysis was performed using self-rated health factors as dependent variables, living activities as independent variables, and sex, age (<50 or B50 years), and annual income (<4 or B4 million yen) as confounding factors. Survey items were divided into dependent variables and independent variables as follows, and all data were analyzed using SPSS 19.0J for Windows. 1) Dependent variables 1Subjective health: Excellent or good and moderate, poor, or very poor 2Sleep and rest: Sufficient or moderate and little or none 3Subjective happiness (on a scale of 0-10): 8-10 and 0-7 2) Independent variables 1Frequency of baths per week (all year round, summer, spring or fall, and winter): bathe daily and not bathe daily 2 Frequency of showers per week (all year round, summer, spring or fall, and winter): shower only and other 3Frequency of utilizing onsen facilities (all year round, summer, spring or fall, and winter): at least monthly and less than monthly 4Daily consumption of brewed green tea: at least 500 ml and less than 500 ml 5Daily consumption of canned or bottled green tea: at least 200 ml and less than 200 ml 4. Ethical considerations This study analyzed data from the 2012 Shizuoka Resident Awareness Survey, and the data set was provided by Shizuoka Prefecture in an anonymized form. This study was approved by the Ethics Committee of the Japan Health & Research Institute. III RESULTS We received survey responses from 3,054 of the 6,000 residents (response rate, 50.9%). Of the respondents, 1,389 (46.0%) were men and 1,631 (54.0%) were women. The number of respondents in each age group was 319 (10.5%) for age years, 362 (12.0%) for years, 441 (14.6%) for years, 544 (18.0%) for years, 679 (22.6%) for years, and 684 (22.6%) for B70 years. The survey results revealed that 52.7% of participants took baths daily all year round, 57.3% in summer, 66.3% in spring or fall, and 69.5% in winter. The percentage of participants who took showers daily was 13.2% all year round, 22.2% in summer, 9.9% in spring or fall, and 5.5% in winter. In addition, 23.4% of the participants visited onsen facilities at least once a month all year

4 174 Y. GOTO et al. round, 27. 3% in summer, 33. 8% in spring or fall, and 33. 7% in winter. Lastly, 38. 1% of the participants consumed tea from brewed leaves, whereas 16. 5% consumed canned or bottled green tea (Table 1). Overall, 72.3% (n=2,176) of participants reported good SRH and 27.7% (n=834) reported poor SRH. Good SRH showed significantly high odds ratios for bathe daily (all year round: OR=1.27, 95%CI ; p=0.012, summer: OR=1.25, 95%CI ; p=0.028, spring or fall: OR=1.45, Table 1 Characteristics of respondents and the proportion of variable groups

5 Contribution of Seasonal Bathig, Onsen and Green Tea to Good Health Status %CI ; p < ), and winter: OR = 1. 44, 95%CI ; p < ) and for the combination of at least 500 ml of brewed green tea and bathe daily: OR=1.24, 95%CI ; p= In contrast, poor SRH was significantly correlated with at least 200 ml of canned or bottled green tea: OR=0.74, 95%CI ; p=0.018 and shower only (all year round: OR=0.75, 95%CI ; p=0.029, and winter: OR=0.59, 95%CI ; p=0.005) (Table 2). Sufficient sleep quality and rest was reported by 84.3% of respondents (n=2,518). Sufficient sleep and rest showed a significantly high odds ratio for bathe daily (all year round: OR=1.41, 95%CI ; p=0.003, summer: OR=1.43, 95%CI ; p=0.003, spring or fall: OR=1.87, 95%CI ; p < , and winter: OR = 1. 67, 95%CI ; p < ). In contrast, insufficient sleep and rest was significantly correlated with shower only (all year: OR=0.69, 95%CI ; p=0.012, and winter: OR=0.65, 95%CI ; p=0.047) (Table 3). Furthermore, subjective happiness was rated as being high by 51. 7% (N = 1, 555) of the participants, and bathes daily (all year round: OR=1.35, 95%CI= ; p<0.001, summer: OR= 1.27, 95%CI= ; p=0.006, spring or fall: OR=1.42, 95%CI= ; p<0.001, and winter: OR= 1.42, 95%CI= ; p<0.001) and utilizes onsen facilities at least monthly (all year round: OR =1.25, 95%CI= ; p=0.021, summer: OR=1.31, 95%CI= ; p=0.003, spring or fall: OR= 1. 27, 95%CI = ; p = , and winter: OR = 1. 29, 95%CI = ; p = ) showed significantly high odds ratios. On the other hand, low subjective happiness ratings were associated with showers only (all year round: OR=0.66, 95%CI= ; p<0.001, summer: OR= 0.78, 95%CI= ; p=0.010, spring or fall: OR=0.66, 95%CI= ; p=0.003, and winter: OR= 0.47, 95%CI= ; p<0.001) (Table 4). IV DISCUSSION In our previous study, bathing daily, utilizing onsen facilities, and drinking a large amount of green tea was found to improve subjective health, suggesting that incorporating these activities into daily living improves health similarly to nutritionally balanced meals, exercise, adequate sleep, and low stress level11). The present study further investigated the health effects of bathing, onsen utilization, and green tea consumption by including detailed survey items. 1. Bathing In our previous study, bathing daily (all year round) was associated with improved subjective health, sufficient sleep and rest, and low stress level 11). In the present study, we further investigated the effect of seasonal variations in bath and shower habits. The results showed that bathing daily was associated with good subjective health, sufficient sleep and rest, and high subjective happiness, regardless of the season. On the other hand, taking showers only was associated with poor subjective health, insufficient sleep and rest (except in summer), and low subjective happiness. Bathing, a characteristic of the Japanese lifestyle, causes dilation of the blood vessels and greatly improves functioning of the cardiovascular system. Due to improved blood flow, oxygen is delivered to all parts of the body, and metabolic waste that accumulate every day are removed

6 176 Y. GOTO et al. Table 2 Association between subjective health and variable groups

7 Contribution of Seasonal Bathig, Onsen and Green Tea to Good Health Status 177 Table 3 Association between sleep quality and rest and variable groups

8 178 Y. GOTO et al. Table 4 Association between subjective happiness and variable groups

9 Contribution of Seasonal Bathig, Onsen and Green Tea to Good Health Status 179 from the extremities 5),6),12),13). These beneficial effects are believed to be small in individuals who take a shower only, which does not adequately warm the entire body. The results of this study support the notion that taking a bath every day regardless of the season is an effective means to keep the body refreshed. 2. Utilizing onsen facilities Our previous finding of an association between the utilization of onsen facilities at least monthly and improved subjective health 11) led us to investigate here the effects of seasonal variation in onsen utilization. As a result, we found that utilizing onsen facilities at least monthly is associated with good subjective happiness regardless of the season. In a 3-year follow-up study by Kagamimori et al., utilization of onsen facilities reduced the incidence of cerebrovascular diseases and bone fracture, and resultant deaths 7). Sekine et al. also reported that individuals who visit onsen resorts more often have better mental health 14), indicating that out-of-theordinary recreation activities can help to improve and maintain mental health. Therefore, for the sake of improving one s health, it is sometimes necessary to take a break from routine daily activities by enjoying onsen facilities. 3. Green tea consumption Daily consumption of at least 1Lofgreen tea was associated with improved subjective health in our previous study 11) ; therefore, in the present study we investigated the effect of daily green tea consumption via brewed tea leaves, cans, and plastic bottles. Interestingly, while daily consumption of at least 500 ml of brewed green tea was associated with good subjective health, daily consumption of at least 200 ml of canned or bottled green tea was linked to poor subjective health. Through the effects of catechin, green tea not only prevents obesity, diabetes, and infection, but also reduces the incidence of arteriosclerotic diseases that are caused by the inhibition of antioxidants by low density lipoprotein 15),16). It is interesting that the purchase volume of green tea in Shizuoka prefecture is the most among all of the 47 prefectures in Japan (the purchase volume; Shizuoka prefecture: 1,901g, National average: 986g, Family Income and Expenditure Survey by Ministry of Internal Affairs and Communications) and the life expectancy in Shizuoka prefecture of men is the sixth place and of women is the sixteenth among 47 prefectures all over Japan (abridged life table in 2013 by Ministry of Health, Labour and Welfare). It is also impressive that residents in Nara and Kyoto prefecture in which the purchase volume of green tea is the second and the third favorite show the longer life expectancy compared with the one in national average. The present study as well found that drinking green tea from brewed tea leaves every day can promote and maintain health, indicating that this habit should be proactively incorporated into daily living. It is imaginable that happiness, health, and longevity may be the most important key words when people express their well being. It has been shown that either of subjective health and subjective happiness are related to one s health and longevity 17)18). In addition, even though healthy people must not have diseased condition physically and mentally, people who show high sense of subjective health have low mortality rate with or without diseased condition. The result

10 180 Y. GOTO et al. which showed the relation between subjective health and bathing in bathtub every day and the daily consumption of brewed green tea at least 500mL in our study may presume that these daily habit may contribute to prolong people s longevity. Subjective happiness is a parameter which is more influenced by one s moods or emotion such as life satisfaction and optimism. In our study, subjective happiness was not correlated with drinking green tea and related to bathing daily as a daily habit, which suspected that bathing particularly may have good effect not only physically but also mentally among various daily habits. Onsen visit also show the relation with subjective happiness and we think that bathing and onsen visit may have strong meaning of a recreation and a fun for Japanese. 4. Limitation The limitation of this study is that this is a cross-sectional study and it is not possible to discount the possibility of reverse cause. The response rate of men was 46% and the one of women was 54% so that it should be considered that this difference of a questionnaire collection rate between men and women may be occurred some bias with this statistics. Even though the evaluation of the health condition were all subjective in this study and response rate was 50.9%, which is relatively lower compared with other population-based study, this is a large scale statistic survey and we think this study would be reliable. 5. Conclusion We have previously shown that daily bathing, onsen utilization, and green tea consumption are correlated with good subjective health and that the incorporation of these activities into daily life as lifestyle habits can confer the same health benefits as a nutritionally balanced diet, exercise, adequate sleep, and low stress level. This time, in a more detailed investigation of bathing habits, onsen utilization, and green tea consumption, we found that daily bathing all year round, utilization of onsen facilities, and daily consumption of at least 500 ml of brewed green tea are health-improving habits that should to be proactively encouraged in daily living. We believe that the inclusion of a formal recommendation for daily green tea consumption and daily bathing and the establishment of reference values for these habits in the Health Promotion Policy will foster health and longevity in Japanese citizens. ACKNOWLEDGEMENT This study was supported by the Shizuoka prefectural government. We would like to thank the Shizuoka prefectural government and Ms. Maya Akahori and Ms. Atsuko Kawada who kindly collaborated with this research. References 1) Breslow S, Enstrom JE: Persistence of health habits and their relationship to mortality. Predictive Medicine 1980; 9: ) Nakamura Y, Ueshima H, Hayakawa T, et al.: A Japanese Diet and 19-Year Mortality: NIPPON DATA80. Circulation 2007; 116: II_789. 3) Traphagan JW: Culture and long-term care:

11 Contribution of Seasonal Bathig, Onsen and Green Tea to Good Health Status 181 the bath as social service in Japan. Care Manag J 2004; 5: ) Hayasaka S, Shibata Y, Noda Y, et al.: Incidence of symptoms and accidents during baths and showers among the Japanese general public. J Epidemiol 2011; 21: ) Watanabe H, Yorizumi K: Effects of bathing on cerebral blood blow in healthy volunteers using Patlak plot method with Technetium- 99m ethyl cysteinate dimer. J Jpn Soc Balneol Climatol Phys Med 1997; 60 (2): ) Nobuoka S, Aono J, Nagashima J, et al.: Influence of hot bathing on blood flow velocity pattern of peripheral artery. J Jpn Soc Balneol Climatol Phys Med 2006; 63: ) Kagamimori S, Tatsuse T, Nakatani Y, et al.: Does the Hot Spring Contribute to the Active Life Expectancy?: The 3 years follow-up survey in the J town which commenced health promotion facilities using hot spring. J Jpn Soc Balneol Climatol Phys Med 2006; 69: ) Graham N: Green tea composition, consumption and polyphenol chemistry. Preventive medicine 1992; 21: ) Kuriyama S, Shimazu T, Ohmor K, et al.: Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan. JAMA 2006; 296: ) Suzuki S, Miyoshi N and Isemura M: Health promoting effects of green tea. Proc. Jpn. Acad., Ser. B 2012; 88: ) GotoY, Hayasaka S, Nakamura Y: Bathing in hot water, bathing in Japanese style of hot spring and drinking green tea may contribute to the good health status of Japanese. J Jpn Soc Balneol Climatol Phys Med 2012; 75 (4): ) Tei C, Horikiri Y, Park JC, et al.: Acute hemodynamic improvement by thermal vasodilation in congestive heart failure. Circulation 1995; 92: ) Tanaka N, Miyata M, Shimodozono M, et al.: Comparative Study on the Effects of Health Promotion of Single Bathing and 200m Running. J Jpn Soc Balneol Climatol Phys Med 2011; 74 (4): ) Sekine M, Nasermoaddeli A, Wang H et al.: Spa resort use and health-related quality of life, sleep, sickness absence, and hospital admission: the Japanese civil servants study. Complement Ther Med 2006; 14: ) Ohmori R, Iwamoto T, Tago M, et al.: Antioxidant activity of various teas against free radicals and LDL oxidation. Lipid 2005; 40: ) Hirano-Ohmori R, Takahashi R, Momiyama Y, et al.: Green tea consumption and serum malondialdehy demodified LDL concentrations in healthy subjects. J Am Coll Nutr 2005; 24: ) Kaplan GA Perceived health and mortality: a nine year follow-up of human population laboratory cohort. American Journal of Epidemiology 1983; 117 (3): ) Diener E, Chan M: Happy people live longer: subjective well-being contributes to health and longevity. Applied psychology 2011; 3 (1): 1-43.

12 182 Y. GOTO et al. 季節ごとの浴槽浴 温泉施設訪問 緑茶多飲が日本人の健康にもたらす効果 後藤康彰 1),3) 早坂信哉 1),2) 3) 中村好一 抄録背景と目的 : 日常的な浴槽に浸かる温浴 温泉入浴施設の利用 緑茶の多飲は 日本人に特徴的な生活習慣である 我々の先行研究では これらの習慣が 栄養バランスへの配慮 運動習慣 適切な睡眠 低ストレス 禁煙同様よい健康状態と関連するとの結果を得た 本研究では 浴槽浴 シャワー浴 温泉施設利用については季節要因を解析に加え 緑茶については茶葉で煎れた場合 缶 ペットボトルで飲む場合を加えて健康関連自己評価 ( 主観的健康感 睡眠の質 主観的幸福度 ) との関連を検討した 方法 :2012 年に静岡県が県民 6,000 人を対象に実施した自記式アンケート調査項目のうち 主観的健康感 睡眠による休養 主観的幸福度を従属変数に 季節ごと ( 夏 春 秋 冬 ) の浴槽浴頻度 ( 週 7 日 / 週 6 日以下 ) シャワー浴( シャワーだけ / それ以外 ) 温泉施設の訪問頻度( 月 1 回以上 / 月 1 回未満 ) 茶葉で入れた緑茶の1 日あたり飲量 (1 日 500mL 以上 /500mL 未満 ) 缶またはペットボトルの緑茶の1 日あたり飲量 (1 日 200mL 以上 /200mL 未満 ) を独立変数とし 性 ( 男 / 女 ) 年齢(50 歳未満 /50 歳以上 ) 年収(400 万円未満 /400 万円以上 ) を調整因子としたlogistic 回帰分析を実施した 結果 : 調査への回答者は3,054 人 (50.9%) であった 季節に関わらず毎日の浴槽浴は 主観的健康感 (OR=1.27, 95%CI ; p=0.012) 睡眠による休養(OR=1.41, 95%CI ; p=0.003) 主観的幸福感 (OR=1.35, 95%CI= ; p<0.001) が良い状態と有意に関連した また 1 年を通じて月 1 回以上の温泉施設利用する者は主観的幸福感 (OR=1.25, 95%CI= ; p=0.021) が有意に高く 1 日 500mL 以上茶葉で煎れた緑茶を飲む者は 主観的健康感 (OR=1.24, 95%CI ; p=0.039) が有意に高かった 考察 : 季節を問わず毎日の浴槽温浴 1 年を通じた温泉入浴施設利用 茶葉で煎れた緑茶多飲は 主観的健康感がよい状態と関連するとの知見が得られた これらの生活習慣を取り入れることが 健康増進に寄与することが示唆された キーワード : 入浴 温泉 緑茶 主観的健康感 生活習慣 1) 一般財団法人日本健康開発財団温泉医科学研究所 2) 大東文化大学スポーツ 健康科学部健康科学科 埼玉県東松山市岩殿 560 TEL: FAX: ) 自治医科大学公衆衛生学