*2.5. Oral Health Assessment*

Assessment of oral health was conducted by calibrated dental examiners. The examinations were performed under bright artificial lighting while the participants sat on a reclining care chair. Oral health was defined on the basis of the number of remaining teeth and oral functions [13,48,49]. In this study, we determined the number of remaining teeth (remaining root fragments and third molars; min, max: 0, 32) [49] and oral functions (maximum occlusal force, posterior occlusal contact, masticatory performance, oral moisture, and oral bacterial counts). To determine the maximum occlusal force, the participants were asked to bite an Occlusal Force-Meter GM10 (Nagano Keiki, Tokyo, Japan). When one of the first molars was missing, the participants were asked to bite on the closest teeth based on the location of the missing first molar [48,50]. Denture-wearing participants were asked to wear their dentures during the measurements. Masticatory performance (MP) assessment was performed using a test gummy jelly (UHA Mikakuto Co., Ltd., Osaka, Japan). Participants were instructed to chew the gummy jelly 30 times and expectorate all the chewed gummy particles on top of a gauze spread over a paper cup. Masticatory performance was evaluated using the visual scoring method on a 10-point scale (0 = minimum to 9 = maximum) [51]. Posterior occlusal contact was defined as the tooth with an occluding antagonist, which may be a natural dentition or a fixed denture [15,21]. According to Eichner's classification, the occlusal contact in each of the premolar and molar regions was classified into group A (occlusal contact in all four occlusal contact zones), group B (occlusal contact in one to three occlusal contacting zones), and group C (no antagonist contacts in the dentition) [15,21]. In this study, the participants were divided into three groups according to the availability of posterior teeth as the posterior occlusal contact; Eichner A1, A2, A3, B1, B2, and B3 (Figure 2A, "with posterior occlusion (w/PO) group"), Eichner B4, C1, and C2 (Figure 2B, "without posterior occlusion (w/o PO) group"), and Eichner C3 (Figure 2C, "edentulous group") [19].

**Figure 2.** Classification of the Posterior Occlusal Contact: (**A**) With posterior occlusion (with PO) group consisting of Eichner A1, A2, A3, B1, B2, and B3; (**B**) Without Posterior occlusion (without PO) group consisting of Eichner B4, C1, and C2 [52]; (**C**) the edentulous group [53].

Oral moisture was assessed twice by measuring the wetness on the dorsum of the tongue and buccal mucosa using an oral moisture meter (Mucus®, LIFE Co., Ltd., Saitama, Japan). A dielectrophoretic impedance measurement method (Panasonic Healthcare Co., Tokyo, Japan) was used to evaluate the bacterial count on the tongue surface [54,55]. The machine rates bacterial counts from levels 1 to 7 [56]; level 1, 2, 3, 4, 5, 6, and 7 indicate the bacterial counts of <105, ≥10<sup>5</sup> and <106, ≥10<sup>6</sup> and <3.16 × <sup>10</sup>6, ≥3.16 × 106 and <107, ≥10<sup>7</sup> and <3.16 × 107, ≥3.16 × <sup>10</sup>7, <108, and ≥108, respectively [49].

#### *2.6. Nutrition Assessment Methods*

Dietary intakes were evaluated using a brief-type self-administered diet history questionnaire (BDHQ), a previously validated fixed-portion type food frequency questionnaire [37]. This questionnaire explores the general dietary habits, cooking methods, and intake frequency of 58 foods and beverages consumed in Japan, including the daily intake of rice and miso soup, consumption frequency of non-alcoholic beverages, and the amount per drink consumed for five alcoholic beverages [36]. In this study, we asked the participants about the consumption frequency of selected foods during the previous month, without mentioning portion size, while a managerial dietician or investigator helped them complete the questionnaire. The food groups included in the BDHQ were meat, fish, vegetables, fruits, cereals, seasonings/condiments, fermented soybean paste (miso), noodle soup, confectionaries, alcoholic and non-alcoholic beverages, and dairy products. The participants were asked about the consumption frequency of each food (once a day, twice or more daily, once a week, 2–3 times a week, 4–6 times a week, less than once a week, or did not eat/drink). Using the responses for BDHQ and an ad hoc computer algorithm based on the Standard Tables of Food Composition in Japan, the daily intake of food items, mean daily intake of energy, and chosen nutrients were determined [35–37]. High sodium intake was reported to be associated with hypertension; however, potassium intake or sodium-to-potassium ratio must also be considered [57]. Hence, we calculated the sodiumto-potassium ratio from the quantities of sodium and potassium intake from the BDHQ data [40]. Although this has not been validated yet, previous studies have reported that the high potassium intake or low sodium-to-potassium ratio may have beneficial possibilities for BP [57]. Daily alcohol consumption was calculated as a part of the BDHQ [35,37]. The data used in this study were coded to preserve the anonymity of the participants.
