We analyzed baseline data from the population-based Kyoto-Kameoka Study, which aimed to examine the associations between food intake, nutritional status, physical activity, oral function and long-term care (LTC) insurance among the community-dwelling older people in Kyoto prefecture, Japan. 14 The study participants and methods used in the Kyoto-Kameoka Study have been described in detail elsewhere. 14 The Daily Life Area Needs Survey was conducted by mail among 18231 elderly people aged 65 years or older living in Kameoka City, Kyoto Prefecture (as of July 1, 2011), excluding those who required nursing care levels is 3 or more, and 13159 of them responded (response rate: 73.2%). Second, after excluding 69 people who died and those who required support or care, an additional survey of 12054 people was conducted in February 2012, and the number of respondents was 8,319 (response rate: 69.4%).
From the 8319 participants, we further excluded 2681 who met any of the following conditions: missing data on the consumption of green tea (n=375) and Kihon Checklist score (n=2276). Finally, 5668 participants were eligible for this study (2766 men and 2902 women). We described the study concept in the mail survey. Participants gave informed consent by returning the questionnaire with the participant’s name. The entire study protocol was reviewed and approved the Ethics Committees of Kyoto Prefectural University of Medicine (RBMR-E-363), Kyoto University of Advanced Science (No. 20-1), and the National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN-76-2) and that it conforms to the provisions of the Declaration of Helsinki.
The entire study protocol was reviewed and approved the Ethics Committees of Kyoto Prefectural University of Medicine (RBMR-E-363), Kyoto University of Advanced Science (No. 20-1), and the National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN-76-2) and that it conforms to the provisions of the Declaration of Helsinki. Participants gave informed consent by returning the questionnaire with the participant’s name.
Dietary intake was assessed using a commonly used previously validated Japanese food frequency questionnaire (FFQ).15, 16 In this FFQ, we asked participants to report their intake frequency to assess the average intakes of 46 foods and beverages (green tea and coffee) items over the past year. The frequencies of green tea consumption were categorized as follows: almost none, 1 to 3 times/month, 1 to 2 times/week, 3 to 4 times/week, 5 to 6 times/week, 1 time/day, 2 times/day, and ≥3 times/day. The total energy intake was calculated using a program developed by Tokudome et al,15, 16 based on the standard tables of food consumption In Japan (fifth revised edition).17
Definition of frailty
In Japan, the Kihon Checklist (KCL) was developed by the Japanese Ministry of Health, Labor and Welfare to screen for future risks of LTC certification.18, 19 Recently, the KCL was validated for use in screening community-dwelling older residents for frailty,18 it was translated to other languages and used in various countries.20 The strengths of the KCL include its use in the assessment of physical, sociological, and psychological domains as a comprehensive questionnaire: 1) questions 1-5 assessed “instrumental activities of daily living (IADL)”, 2) questions 6-10 “physical function/strength”, 3) questions 11-12 “malnutrition”, 4) questions 13-15 “oral function/eating”, 5) questions 16-17 “socialization/housebound”, 6) questions 18-20 cognitive/memory, and 7) questions 21-25 “depression/mood”.19 When the dichotomous response (yes / no) fell under a risk of frailty, the score is pointed + 1. A high KCL score (range 0-25) indicates worse functioning and severe frailty. The total score of original KCL ≥7 points was indicated a higher risk of long-term care. 21 The cut-off point at which problems were defined for the following seven domains are as follows: 1) IADL score ≥3 points, 2) mobility disability ≥3 points, 3) nutrition 2 points, 4) oral or eating function ≥2 points, 5) socialization and housebound problems were indicated in people who answered ‘no’ to Q16 (Do you go out at least once a week?), 6) cognitive function ≥1 points, and 7) depression ≥2 points.
A self-administered questionnaire was used to assess height, weight, alcohol consumption status, and smoking status. Alcohol consumption status was classified into the following categories: everyday, sometimes, seldom, and never. Smoking status was classified into the following: everyday, sometimes, formerly, and never. BMI was calculated as the self-reported body weight (in kg) divided by the square of the self-reported height (in m2).
All statistical analyses were performed separately for men and women with the SAS statistical software package (Ver. 9.4 for Windows; SAS Institute, Cary, NC, USA). We categorized their green tea consumption based on their beverages consumption distribution as follows: almost none, <1 cup/day, 1-2 cups/day, ≥3 cups/day for green tea. The participants’ characteristics according to categories of green tea consumption were compared by linear regression analysis (for continuous variables) or Mantel-Haenszel test (for categorical variables), as appropriate. Adjusted odds ratio (ORs) and 95% confidence intervals (CIs) for frailty risk according to the consumption of green tea was estimated using logistic regression analysis. Adjustments were made for age (years, continuous), BMI (kg/m2, continuous), total energy intake (kcal/day, continuous), alcohol consumption status (everyday, sometimes, seldom, or never), smoking status (everyday, sometimes, formerly, or never). We found that subjects with higher consumption of green tea were more likely to consume coffee. We further adjusted for coffee consumption (almost none, <1 cup/day, 1 cup/day, or ≥2 cups/day) in each model as covariate. A P value <0.05 was considered statistically significant.