Participants
This cross-sectional study was derived from another study investigating the determinants of walking movements of rural residents. This study was conducted by extracting only the data of elderly people over 60 years of age to study sarcopenia.
The survey was initially conducted in two areas in Gyeongsangnam-do that are designated for research purposes. The number of study subjects was determined to be 1,450, calculated with a confidence level of 95% and a sample error of ± 2.1% p in a population size of 5,700. Subjects were assigned households with an even number based on the street address of the area, and after confirming in the administrative data the number of residents over the age of 19 who were said to be alive, approximately 1,600 people were assigned. The survey consisted of a face-to-face questionnaire administered by six researchers who had received training and practice training twice on how to collect data and how to administer face-to-face questionnaire surveys. Data were collected for about two months beginning in June 2018. The subjects of the study were those who could precisely answer the questions after listening to the questionnaire, and those who agreed to participate in the study were included. Among the 1,600 people assigned, 1,500 were surveyed, excluding those who were not alive at the time of the investigation or who refused to participate. Of the 1,500, only 1,019 subjects aged 60 years or older were selected as study subjects.
This study was conducted with the approval of the Institutional Review Board of Gyeongsang National University (GIRB-A18-Y-0027).
Materials
The exposure variables in this study were nutritional deficiency and sociopsychological factors, and the outcome variable was sarcopenia. Demographic characteristics (gender, age, living alone) and socio-economic characteristics (education level, occupation, monthly income) were investigated as correction variables. Occupation was divided into agriculture and others, and the average monthly household income values were divided into the following categories: less than 1 million won, 1 000 to 2 000 dollars, 2000 to 3000 dollars, 3000 to 4000 dollars, and over 4000 dollars.
1) Possible Sarcopenia
The revised Asian guidelines suggested possible sarcopenia concept for community preventive services. “Possible sarcopenia (PS)” was defined by low muscle strength (handgrip strength, M: <28 kg, F: <18 kg) with or without reduced physical performance (5-time chair stand test: ≥12 sec). The measurement was conducted using the Smedley-type dynamometer (TKK 5401; Takei Scientific Instruments Co., Tokyo, Japan) to alternately evaluate each hand twice, and the grip strength used for analysis was the largest of the four measured values.
2) Nutrition
The Mini Nutritional Assessment (MNA), which evaluates the nutritional status of the elderly, was downloaded from the www.mna-elderly.com website and adapted to a Korean version [16]. The tool consists of 18 questions (4 questions from the new system, 6 questions from the overall physical and mental assessment, 6 questions from the dietary assessment, and 2 questions from the self-awareness assessment about health and nutrition), and a total score of 30 is calculated. After calculating the overall score, 23.5 points or more was categorized as good nutrition, 17.0 to 23.5 points as nutritional risk, and 17 points or less as nutritional deficiency. In this study, we categorized subjects with 23.5 points or more as well-nourished and those with 23.5 points or less as at risk of malnutrition.
3) Psychosocial factors
The psychosocial factors examined were self-efficacy, social isolation, fear of falling, and social capital (trust and participation), among those suggested by Tieland et al. [9]
Self-efficacy addressed confidence in performing exercise and proper diet even under the following conditions: takes a long time at one time; needs to be repeated several times until finished; or feeling worried, depressed, anxious, tired, or busy. In order to increase the response rate of questionnaires, the respondents were asked to respond on a scale of 1–7, where 7 is 'very confident', 4 is 'so, so', and 1 is 'not confident'. As a result, if there was high confidence across all situations, the mean score would be 7 points. The mean score was reclassified into a high self-efficacy group (more than 6 points), a medium self-efficacy group (4–5 points), and a low self-efficacy group (less than 3 points).
Social isolation or no social isolation was assigned according to the subject having or not having at least two neighbors (friends) or family members (relatives) with whom they could talk intimately. Fear of falling was assigned according to a ‘Yes’ or ‘No’ response to the following question: Have you ever hesitated to go out because you're afraid of falling?
Social capital assessed social participation in a meeting at least once a month (Yes / No) and trust by neighborhood people (Yes / No).
Statistical analysis
The frequency and average were presented for general characteristics, nutritional deficiencies, and psychosocial factors, and the χ2 and t-test were performed for general characteristics, nutritional deficiency, and psychosocial factors, according to whether or not PS was present.
First, a logistic regression analysis was performed for the relationship between risk of malnutrition and psychosocial factors, with demographic and socio-economic characteristics included as correction variables. Next, a logistic regression analysis was also performed for the relationship between risk of malnutrition, psychosocial factors, and PS. Demographic characteristics and socio-economic characteristics were also included as correction variables. In model 1, correction variables and risk of malnutrition were included; in model 2, correction variables and psychosocial factors were included; and finally in model 3, all variables were included.
All analyses were performed using SPSS 25.0, and statistical significance was defined as 0.05 or less.