Study participants comprised 324 individuals living in six rural villages, and research was conducted at senior and welfare centers. All participants aged 65 years who lived in villages and were able to move to senior and welfare centers were surveyed. Of a population of 351 elderly people, 341 responded that they did not suffer from cognitive impairment, cancer, stroke, or myocardial infarction. A total of 324 participants was finally included in the investigation (341 healthy respondents, excepting 17, who declined to consent to participation). All surveys were conducted on a one-on-one basis after trained researchers interviewed subjects, explained the content of the survey, and obtained written informed consent from the subjects. In addition, this study was approved by the Institutional Review Board of Gyeongsang National University (approval number: GIRB-A19-0031).
Demographic characteristics for investigation were sex, age, marital status, educational status, smoking status, and patient health questionnaire-2 (PHQ-2) survey for depression status. After the survey, the education level was divided into children under 6 years old and over 7 years old. In addition, PHQ-2 results were classified as greater or less than 3 points.
Assessment of nutritional status
To determine the nutritional status of elderly participants, a questionnaire screening tool called DETERMINE was used. This self-written questionnaire consists of 10 questions, with the name, DETERMINE, referring to an alphabetic collection of the first letters (in English) of each item assessed. Thus, questionnaire items consist of Disease, Eating poorly, Tooth loss, Mouth pain, Economic hardship, Reduced social contact, Multiple medicines, Involuntary weight loss or gain, Need for assistance in self-care, and Elderly [people] over 80 years old.
Weights are assigned according to importance. Nutritional risk scores were divided into 0–21 points, with 0–2 points categorizing the low-risk group, 3–5 points for the moderate-risk group, and 6 points for the high-risk group.
Developed as a health-related quality of life tool for sarcopenia, the SarQoL questionnaire consists of 55 items and 22 questions. The questionnaire calculates a total of seven domains with a total score of 0-100 points each.
Scores of survey items are distributed from 0 (worst imaginable quality of life) to 100 (best imaginable quality of life). The domains (enumerated 1–7) and items are as follows: 1) physical and mental health, assessed with eight items, such as loss of arm strength or feelings of being frail, 2) locomotion, assessed with nine items, such as limitations in walking time and difficulty in walking on uneven ground, 3) body composition, assessed with three items, such as loss of muscle mass, 4) functionality, assessed with 14 items, such as balance problems and frequency of falls, 5) activities of daily living, assessed with 15 items, such as difficulty during light physical effort, fatigue during light physical effort, and use of public transportation, 6) leisure activities, assessed with two items, such as changes in leisure activities, and 7) feelings of fear, assessed with four items, such as fear of getting hurt and fear of falling.
SARC-F questionnaire to assess sarcopenia
This questionnaire was developed for screening sarcopenia in the elderly. Question items consist of five categories of strength, assistance required for walking, rising from a chair, climbing stairs, and frequency of falls. Sarcopenia is suspected in patients receiving more than four of 10 points.
Assessment of sarcopenia
In this study, assessment of sarcopenia includes skeletal muscle mass, calf circumference, grip strength, and the timed up and go (TUG) test. The skeletal muscle index (SMI) was calculated using the following bioelectrical impedance analysis (BIA) regression equation (measured by InBody 720, Biospace Co., Ltd., Seoul, Korea): skeletal muscle (kg) = [0.401 × (height2/resistance) + (3.825 × sex) − (0.071 × age) + 5.102]. Low muscle mass was classified as a height-adjusted SMI value < 5.7 kg/m2 for women and < 7.0 kg/m2 for men. Grip strength was measured using an analogue dynamometer (TK 5001 Grip-A, Takei, Tokyo, Japan), and dominant hand grip strength was classified as “robust” if the value was over 28 kg for men and over 18 kg for women. Calf circumference qualified participants for the sarcopenia risk group with a cut-off point less than 34 cm for men and less than 33 cm for women. To measure physical performance using the TUG test, each individual was asked to stand from a sitting position, walk 3 m, and then return to a sitting position on the same chair, during which a trained researcher measured the time (in seconds) required to perform this task. Times were divided into robust and abnormal based on a baseline of 10 seconds.
Frequency and mean scores were recorded. Logistic regression analysis was performed to determine the association between nutritional status and SARC-F. Multiple regression analysis was performed to determine the association between SarQoL and nutritional intake. Nutritional status was included in the analysis as a dummy variable based on a baseline of good. All statistical analyses were performed after adjusting for demographic characteristics (sex, age, living alone, educational level, whether or not participants were smokers), symptoms of depression, muscle mass, calf circumference, grip strength, and TUG. Statistical program SPSS 23.0 was used, and a p-value less than 0.05 was considered statistically significant.