According to the updated diagnostic criteria of the AWGS 2019, we found that the overall prevalence of sarcopenia among people aged 50 years or older was 8.8% and increased with age (5% in the 50–59 years group; 5.8% in the 60–69 years group; 10.3% in the 70–79 years group and 26.2% in the ≥ 80 years group). We identified some nutritional factors associated with sarcopenia, and some interesting results have been found that certain eating habits were associated with sarcopenia.
Prevalence of sarcopenia
The prevalence of sarcopenia also varies greatly according to the diagnostic criteria of sarcopenia and in different populations15. It was reported that, according to the diagnostic criteria developed by the AWGS, the prevalence of sarcopenia is approximately 18% (95% CI: 14–23%) using dual X-ray absorptiometry (DXA) and 14% (95% CI: 11–16%) using BIA16. A Chinese study involving 6172 community-dwelling older adults aged ≥ 60 years showed that the prevalence of sarcopenia is 13.5% in urban areas and 30.9% in rural areas. Meanwhile, sarcopenia also becomes more common in individuals aged 60 years17. The prevalence of sarcopenia in communities aged over 50 in Western China was 19.31%18 and 2.61%-9.72% among those aged over 60 in Eastern China19. In existing studies, the estimated prevalence of sarcopenia varies considerably due to the different diagnostic criteria used, differences in the methods used to measure muscle mass, differences in the cut-off points applied, and heterogeneous study populations16. These factors could all contribute to the large amount of heterogeneity found in the studies. Meanwhile, few studies reported prevalence in individuals younger than 60 years. Therefore, it is particularly important to study the related factors of sarcopenia in this sample population.
Sociodemographic Factors related to sarcopenia
The sociological reasons that influence sarcopenia are known to be diverse, including ageing itself, gender, income, lifestyle, etc.20. However, in previous studies, the factors associated with sarcopenia were varied, and sometimes the results have been inconsistent and controversial20–22. Our study demonstrated that gender, marital status (with or without spouse), and income status were not independent associated factors of sarcopenia. However, the incidence of sarcopenia is higher in older age and people with nutritional risk or malnutrition, which is consistent with previous reports. The prevalence of malnutrition risk has been reported to range from 16–73% among community-dwelling older adults in Asia, whereas the prevalence of malnourishment can be as high as 22%23–25. Several cross-sectional studies in Asia have linked malnutrition and sarcopenia and suggested early identification of associated risk factors in older adults8, 26. There is also growing evidence that nutritional status may be a modifiable risk factor for the development of muscle health problems, including sarcopenia26–28.
Correlation among dietary structure, eating habits and sarcopenia
Recently, the analysis of dietary patterns has emerged as a useful tool to elucidate the relationship between diet and sarcopenia. The results of this study showed that vegetarian participants had a higher risk of sarcopenia (20%) than a balanced diet pattern (8.5%) and meat diet pattern (6.2%). One possible factor thought to contribute to the relationship between vegetarian diets and a higher risk of sarcopenia is the insufficient protein intake of this dietary pattern. Protein intake was positively related to meat product consumption in elderly individuals29. Evidence from a systematic review concluded that protein supplementation may improve muscle strength and function through muscle protein synthesis or preventing muscle breakdown30. In a large-scale cross-sectional study of an elderly Chinese population, three major dietary patterns were identified: the sweet pattern, vegetable pattern and animal food pattern14. This study demonstrated that a higher vegetable and animal food pattern score was related to a lower prevalence of sarcopenia in elderly adults14. However, a cross-sectional study identified a ‘cereals–tubers–animal oils’ pattern, a ‘mushrooms–fruits–milk’ pattern and an ‘animal foods’ pattern in community-dwelling older people from three regions of China31. The ‘animal food’ pattern showed no significant association with sarcopenia in that study31, which indicated that protein and fat might play different roles in the development of sarcopenia. Therefore, more evidence is required to determine the association between dietary patterns and sarcopenia.
Furthermore, in our study, the participants who consumed fruits, nuts and dairy daily had a lower risk of sarcopenia. Oxidative stress plays an important role in the pathogenesis of sarcopenia32. The fruits and nuts provide abundant antioxidants, which may contribute to reduced oxidative stress33. Nuts are rich in plant protein, unsaturated fatty acids, phytochemicals, vitamins and minerals; therefore, these nutrients may act synergistically to prevent and manage sarcopenia in older adults34. To date, there have been no intervention studies on the association of nut consumption and sarcopenia in the open literature. Dairy products are good sources of high-quality protein, mainly in the form of whey or casein35. They require no cooking or minimal preparation, making dairy sources a practical option for seniors to consume adequate protein36. Evidence from a systematic review demonstrated that dairy product consumption in older adults may reduce the risk of frailty, particularly high consumption of low-fat milk and yogurt, and may also reduce the risk of sarcopenia by improving skeletal muscle mass by adding nutrient-rich dairy proteins to the habitual diet37. Another systematic review and meta-analysis suggested that dairy proteins, at an amount of 14–40 g/d, can significantly increase appendicular muscle mass in middle-aged and older adults without a significant clinical effect on handgrip strength and leg press38.
Meanwhile, our research team also found for the first time that the participants who consumed spicy eating habits had a higher risk of sarcopenia. Whether a spicy eating habits diet means higher saturated fatty acid intake and hence sarcopenia risk or other pathogenesis remains to be determined.
As shown in Fig. 2, nutritional risk or malnutrition, vegetable diet, advanced age and spicy eating habits were risk factors for sarcopenia; daily fruit, dairy and nut consumption were protective factors against sarcopenia.
Limitations of this study
There are some limitations that should be considered in the present study. First, the cross-sectional study design leads to the uncertainty of a causal relationship; therefore, future prospective studies are needed to confirm the causal relationship between sarcopenia and dietary factors in the Chinese elderly population. Second, all participants were from Beijing, the northern capital of this large country. Therefore, the results might not apply to other populations. Third, due to the COVID-19 pandemic, the sample size of this study was not sufficient, which affected the group discussion and analysis of related factors. Finally, this study did not investigate the daily nutrient intake of the subjects but only analysed the dietary structure, which needs to be further improved in follow-up studies. As a result, other potential dietary patterns beneficial to sarcopenia might not have been identified in the present study. Finally, we cannot rule out the possibility that unmeasured factors might contribute to the association observed.