2.3. Collection of Data

The following data were selected at the responsibility of the investigators, and each test was applied correctly in all cases.

We collected data for the following variables: age (years), sex, body mass index (BMI; calculated as kg/m²), self-reported physical activity (engaged in physical activity regularly [yes] vs. does not engage in physical activity regularly [no]), number of falls in the past year, and muscle mass.

Body composition and body weight were measured using the bioelectrical impedance analysis method with an MC-780A multi-frequency segmental body composition analyzer (Tanita Co., Tokyo, Japan) [29,30]. The muscle mass (kg) of the arms and legs and BMI were automatically calculated [31]. Body height was measured using a stadiometer.

The number of remaining teeth was counted by a dentist or trained dental hygienist [27,32]. Salivary occult blood was evaluated using a urine occult blood test paper and a 5-point Likert scale (1, no occult blood; 5, severe disease [33,34,35]).

Masticatory function was objectively assessed using gummy jelly (Gumi 15; soft chewy candy: Sugarless Fine Gummy, Fine Co., Ltd., Tokyo, Japan). Participants using dentures were asked to chew the gummy jelly as vigorously as possible, while wearing the denture, for 15 s to make the jelly as small as possible. Then, they were instructed to spit it into a paper cup. The number of gummy jelly pieces larger than approximately 3 mm was counted to obtain the 15-s gummy value. Based on previous research [32], the study participants were then divided into two categories; those with less than 12 gummy jelly pieces (low group) available and those with 12 or more gummy jelly pieces (high group) available.

Bone status was measured by quantitative ultrasound (QUS) using a Benus α system (Ishikawa Seisakusho, Ltd., Ishikawa, Japan). QUS enables evaluation of bone quality, especially the microarchitecture of the calcaneus, and has the advantages of zero radiation exposure, low cost, and portability. The estimated value compared to the young adult mean (%YAM) with the same gender of examine, that is, 100% means the same value as that in healthy young men or women [28].