Sarcopenia (SP) is characterized by an age-related loss of skeletal muscle strength and athletic ability. It is the leading cause of physical weakness, dysfunction, poor health-related quality of life, and the risk of early mortality in the aged [1] . As the Chinese population ages, the incidence of sarcopenia will surely increase.

In 2000, projected direct medical expenditures for sarcopenia in the United States were $18.5 billion [2] . At the same time, in Europe, the cost of hospitalization for older patients with sarcopenia was five times that of senior patients without sarcopenia [3] . A large community study in the Czech Republic discovered that the direct healthcare expenses for older individuals with sarcopenia were more than twice as high as those without sarcopenia [4] .

The prevalence of sarcopenia varies according to study samples, definitions, and assessment methodologies [5] . Many studies have shown that age [6] , BMI [7] , fat mass [8] and basal and total energy metabolism [9] are the primary determinants of sarcopenia. Therefore, this study assumes that age, BMI, fat mass, basic metabolism, and total energy metabolism are the primary influencing factors of sarcopenia in Zhuang older adult individuals in Southwest China and investigates the correlation between these factors and sarcopenia in Zhuang older adult individuals in Southwest China.

The makeup of the human body will alter dramatically with age, which is most apparent in the senior population, and there are regional and ethnic variations. Studies imply that racial differences in muscle mass [10] are influenced by genetics [11] , hormones [12] , and lifestyles [13] .

The Zhuang population is the most populous ethnic minority in China, with a population of 19.568 million, mainly living in the Guangxi Zhuang Autonomous Region. They have a long history and splendid culture, but they also face some health differences, such as a higher incidence of osteoporosis and a lower life expectancy than other ethnic groups in China. At present, the incidence and influencing factors of sarcopenia in the Zhuang population are not clear, and it is not clear whether there are differences with other ethnic groups. Therefore, this study will investigate the prevalence and risk factors of sarcopenia in the elderly Zhuang population in China, and provide evidence-based interventions to improve their muscle health and quality of life, which will help to narrow these differences.

The aim of this study was to compare the body composition and sarcopenia status of elderly Zhuang people in southwest China, and to reveal the significant differences among elderly Zhuang people and their implications for healthcare planning and policy making. This study is the first to use standardized and validated methods to estimate the prevalence and risk factors for sarcopenia in elderly Zhuang people in China. It is also the first study to investigate the relationship between BMI, fat mass, total energy metabolism and sarcopenia in elderly Chinese Zhuang people, suggesting that some modifiable factors may prevent or delay sarcopenia. The main findings of this study are as follows: (1) The prevalence of sarcopenia among Zhuang people in southwest China was 29.37%, with 30.59% in males and 28.44% in females; (2) Sarcopenia patients are older and have lower BMI, muscle mass, fat mass, basal metabolism and total energy metabolism.

The incidence of sarcopenia has been studied previously shown that sarcopenia affects 1% to 29% of people of various ages and locales [15] , including 14% to 33% of those who require long-term care [16] . In hospitals, 29.7% of older males and 23.0% of older females had sarcopenia. At sanatoriums, 26.3% of elderly males and 33.7% of older females had sarcopenia [17] . This study’s findings match the previous one, despite regional health and sanatorium admittance norms. However, a study in Türkiye found that the frequency of sarcopenia was 5.2% [18] . In Asian Japan, the prevalence of sarcopenia in men and women was 11.5% and 16.7%, respectively [19] . This is quite different from the results of our study, which may be caused by different races [10] , genes [11] , hormones [12] and lifestyles [13] .

Sarcopenia patients had a higher age, The experimental data suggests the following: In older adults, age is an independent negative predictor of skeletal muscle mass index (β = −0.021, R² = 0.819, p < 0.001). Muscles and α-motor neurons change with age. Decreased growth hormone and sex steroid hormone production accelerates muscle ageing [20] . This correlation between age and the likelihood of having a low skeletal muscle mass index was strong [6] [21] . This was consistent with the findings of this study. Age is also a risk factor for sarcopenia in this study (OR = 1.115, 95% CI: 1.086 - 1.144, p < 0.001). The sarcopenia group’s mean age was older than the non-sarcopenia group’s (p < 0.001) [22] . This is consistent with previous findings.

According to this research, male skeletal muscle mass index is significantly high. This is in line with past research [22] - [24] . This research also discovered that men were at a greater risk of sarcopenia (OR = 11.860, 95% CI: 5.691 - 24.717, p < 0.001). This corresponds to earlier reports [24] [25] . Gender may be used as an independent predictor (β = 0.585, p < 0.001) of skeletal muscle mass index in older adult. In terms of gender, the male sarcopenia group outperformed the female sarcopenia group in age, muscle mass, fat mass, basal metabolism, and total energy metabolism (p < 0.001). Male sarcopenia patients have a younger age than female sarcopenia patients. When BMI is less than 24 kg/m², males have a higher detection rate of sarcopenia than females, but in the overweight group, females have a higher detection rate, which may be attributed to the small sarcopenia group. One research discovered that males had greater myostatin mRNA levels than females [26] , and male muscle mass dropped at double the rate of females of the same age [27] , explaining why males were more prone to sarcopenia.

In the older adult, BMI may be used as an independent predictor of skeletal muscle mass index and is positively connected with it (β = 0.313, R² = 0.819, p < 0.001). According to Japanese research, BMI is highly related to skeletal muscle mass index [7] . A low BMI was connected with a greater likelihood of a low skeletal muscle mass index [21] . The results of this research were similar to the findings of the previous investigations, which all concluded that the skeletal muscle mass index was positively connected with BMI [28] . This research discovered that BMI (OR = 0.193, p < 0.001) was a protective factor for sarcopenia. Moderate increases in BMI have been proven in studies to lessen the incidence of sarcopenia in older adults [22] [25] . Body mass index (BMI) and skeletal muscle mass index (SMMI) were considerably lower in the sarcopenia group than in the non-sarcopenia group [29] . The findings of this investigation support these conclusions. However, research conducted in the United States found that the proportion of people with impaired muscle function rose with increasing body mass index [30] , which contradicted this study’s findings. One potential explanation is that people with poor muscle function and limited action ability were eliminated from the included population in this experiment. Consequently, there were no participants with impaired muscular function, resulting in the opposite outcomes of this research in the United States.

Fat mass (β = −0.116, R² = 0.819, p < 0.001) may be used as an independent predictor of sarcopenia. The research found a negative relationship between skeletal muscle mass index and overall fat mass [8] . Studies have indicated that myostatin expression is connected with intramuscular fat (r = 0.29, p < 0.05) in the middle thigh, [26] increasing intramuscular fat in the middle thigh would increase myostatin expression, so further lowering muscle mass; this might explain the results of this research.

Sarcopenia is associated with increased fat accumulation (OR = 1.952, 95% CI: 1.769 - 2.154, p < 0.001). Fat mass was shown to be a risk factor for sarcopenia. Some researchers suggest that increasing total fat might cause muscle fat formation by boosting pro-inflammatory cytokines, resulting in a negative relationship between fat level and skeletal muscle quality [31] . In a study of 3075 people, it was found that too much body fat was associated with too little muscle mass [32] . According to certain research, fat loss predicts muscle function better than defatted muscle loss [33] . A higher body fat percentage is linked to a greater risk of skeletal muscle loss [21] .

Sarcopenia is caused by a combination of factors, including insulin resistance, inflammation, oxidative stress, and hormonal abnormalities [34] . Many studies have shown a link between muscle cytokine production and muscular contraction. Thus, compared to young individuals, older adults who do not exercise may have cytokine imbalances that contribute to a pro-inflammatory state and metabolic dysfunction, increasing important cascades of muscle loss and fat gain [35] . The increased fat mass may worsen sarcopenia because persistent lipid accumulation impairs amino acid binding and muscle protein synthesis [36] . Previous research found a negative trend in fat mass in sarcopenia patients, with female sarcopenia individuals decreasing more considerably, which contradicted the findings of this study [37] . This result could be attributed to the subjects’ different races [38] , regions, or lifestyles.

Total energy metabolism in the older adult may be used as an independent predictor of skeletal muscle mass index and is positively connected with it (β = 0.001, R² = 0.819, p < 0.001). Because basic metabolism and total energy metabolism are collinear, the link between basic metabolism and total energy metabolism and skeletal muscle mass index is likewise positively associated. This study focuses on just one of them. The research findings on whole-body energy metabolism and biochemical features of skeletal muscle reveal that differences in muscle biochemistry contribute to the diversity in muscle oxygen uptake and whole-body energy metabolism across people (metabolic rate and substrate oxidation) [39] . Muscle tissue helps in energy metabolism [40] . Its increased skeletal muscle mass enhances the hydrolysis of triglyceride-rich lipoproteins by boosting the lipoprotein lipase (LPL) and high-density lipoprotein binding protein 1 (GPIHBP1) cycles, hence enhancing energy metabolism [41] . Consequently, the skeletal muscle mass index is substantially connected with the basal metabolic rate (r = 0.72, β = 30.96, p < 0.01) [9] , which is consistent with the findings of this research.

Total energy metabolism is lower in sarcopenia patients than in non-sarcopenia patients. This shows that energy metabolism can predict and prevent sarcopenia. In a clinical study of 22 adults aged 65 years or older, the decreased ability of skeletal muscles to regulate energy expenditure to meet basic physical energy requirements may explain the muscle strength and physical limitations associated with sarcopenia [42] . Another rhesus monkey research discovered that alterations in energy metabolism directly cause skeletal muscle aging [43] . Similarly, research on overweight persons revealed that abnormalities in energy metabolism may result in muscle integrity loss [44] . Oxidative modification damages energy metabolism, which accelerates muscle satellite cell ageing and damage, which could explain this experiment’s results [45] . However, research on linked illnesses revealed that hypermetabolism could result in a loss of muscle mass, which contradicted the results of this trial [46] . It is possible that none of the participants in this study had hypermetabolism.

The prevalence rate of sarcopenia climbed with age and was higher in Zhuang than in other ethnic groups in China. Male participants had a substantially greater frequency of sarcopenia than female participants. Sarcopenia Zhuang’s ageing population had reduced fat mass, basal metabolism, and total energy metabolism.

This work was supported by the Self-funded project of scientific research and technology development plan in Baise, Guangxi, China [ID: 20230531].

This study complied with the Declaration of Helsinki and was approved by the Ethics Committee of Ethics Review Committee of Youjiang Medical University for Nationalities (ethics approval number: 2022053001). All persons gave their informed consent prior to their inclusion in the study.

*Co-first author.

^#Corresponding author.