Introduction

Sarcopenia is characterized by a progressive loss of skeletal muscle mass, strength and performance [1]. Although it has been included in the 10th edition of the International Classification of Diseases Clinical Modification (ICD-10-CM) with a disease code M62.84 by the World Health Organization (WHO), it is still a common but low level of awareness disease among older adults. In this global aging environment, sarcopenia is associated with many age-related chronic diseases, which may increase the incidence of falls in older adults [2], fractures [3], functional limitation and physical disability [4], and all-cause mortality [5], contributing to poor quality of life. As a previous systematic review reported, sarcopenia affects 9.9%-40.4% of community-dwelling older adults worldwide [6], although some estimates are as high as 60% [7]. These great variations in the prevalence of sarcopenia might be primarily explained by different diagnostic criteria for sarcopenia.

Several guidelines have been published for the early identification, diagnosis and management of sarcopenia. The European Working Group on Sarcopenia (EWGSOP) introduced the first consensus diagnostic criteria for sarcopenia in 2010 [8]. The EWGSOP recommended using the presence of both low muscle mass and low muscle function (strength or performance) for sarcopenia diagnosis and provided the cutoff points of muscle mass, muscle strength, and physical performance with slowing walking speed (≤ 0.8 m/s) or low grip strength (< 20 kg for women and < 30 kg for men, respectively), indicating the onset of sarcopenia. In 2011, the International Working Group on Sarcopenia (IWGS) published the second consensus definition for sarcopenia [9]. The IWGS suggested the diagnosis of sarcopenia as a gait speed less than 1 m/s and objectively measured low muscle mass (appendicular skeletal muscle mass relative to square of height (ASM/height2) ≤ 7.23 kg/m2 in men and ≤ 5.67 kg/m2 in women respectively). The American Foundation for the National Institutes of Health (FNIH) also published their official consensus in 2014. Given the differences in ethnicity, genetic background, diet pattern, and body size, these criteria might not be appropriate for Asians [10]. Thus, the Asian Working Group for Sarcopenia (AWGS) established a consensus for sarcopenia diagnosis appropriate to Asians in 2014 [11]. The AWGS agreed with previous reports that sarcopenia should be described as low muscle mass plus low muscle strength and/or low physical performance. The AWGS recommended cutoff values for muscle mass (≤ 7.0 kg/m2 for men and 5.4 kg/m2 for women by dual X-ray absorptiometry, and ≤ 7.0 kg/m2 for men and 5.7 kg/m2 by using bioimpedance analysis for women) appropriate for Asians. In 2018, the EWGSOP updated the original definition for sarcopenia to increase the consistency of clinical diagnoses [12]. The EWGSOP2 focused on low muscle strength as a key characteristic of sarcopenia. Specifically, sarcopenia is probable when low muscle strength is detected, and sarcopenia is confirmed by the presence of low muscle quantity or quality. When low muscle strength, low muscle quantity/quality and low physical performance were all detected, sarcopenia was considered severe. To increase the harmonization to sarcopenia studies, the EWGSOP2 recommended cutoff points for low muscle strength (grip strength < 27 kg for men and < 16 kg for women, chair stand > 15 s for five rises), low muscle quantity (ASM < 20 kg for men and < 15 kg for women, ASM/height2 < 7.0 kg/m2 for men and < 5.5 kg/m2 for women), and low physical performance (gait speed ≤ 0.8 m/s, Short Physical Performance Battery (SPPB) ≤ 8 points, Time up and Go test (TUG) ≥ 20 s, 400 m walk test noncompletion or ≥ 6 min for completion). Therefore, the use of different cutoff values, different techniques used for muscle measurement and study methodologies makes it challenging to accurately estimate the burden of this disease.

China is facing a severe aging situation with a rapid growth of the aging population. According to the latest data of the Seventh National Population Census issued in May 2021, the number of people aged 65 and over reached 190,635,280, accounting for 13.50% of the whole national population [13], and this percentage almost reached a deeply aging society (14%). Compared with the results of the Sixth National Population Census conducted in 2010, the proportion increased by 4.63%. To realize the goal of healthy aging, it is essential to evaluate the overall prevalence of sarcopenia in community-dwelling older Chinese adults. While more recent studies have focused on the prevalence of sarcopenia, the results have been inconsistent among studies [10, 14, 15]. Currently, several systematic reviews have performed meta-analyses to estimate the prevalence of sarcopenia in Chinese community-dwelling older adults. Some reported an overall prevalence (12%) [16], with the key point being mainland China (17%) being higher than that in nonmainland areas (6%). Some separately reported a prevalence based on the AWGS (14%), IWGS (18%) and EWGSOP (10%) [52]. This was consistent with our results that the older the people were, the higher the risk of sarcopenia they would suffer. It must be clarified that not all participants in the included studies could be divided into 65–69, 70–79, 80 years and older subgroups, and the final subgroup analyses based on age were performed only in studies whose participants could be grouped. In addition, men were more likely to suffer sarcopenia than women, which was consistent with previous studies (14% in men vs. 9.11% in women [49]; 13.1–14.9% in men and 11.4% in women [53]). This finding can be explained by the fact that the difference in prevalence between older men and women may be due to lifestyle and smoking or alcohol status [53]. The deleterious influence of lifestyle may be expanded day by day with aging, and all these factors result in sarcopenia. Moreover, Shimokata et al.’s [54] 12-year cohort study also showed that men were more likely to have a significant loss of muscle mass than women.

In the present study, we found that the highest prevalence of sarcopenia defined by the assessment method was the anthropometric measures. As an easy and convenient way to assess the skeletal muscle mass of limbs, it can be used for effective screening for sarcopenia. Although only 3 studies [21, 32, 37] used this measurement tool to define muscle mass, this subjective approach may overestimate the prevalence of sarcopenia. Otherwise, although DEXA was the gold standard to evaluate muscle mass, BIA was more available, cheap, and operable than DEXA and was suitable for extensive screening and diagnosis of sarcopenia in communities and hospitals.

In this meta-analysis, the results of the diagnostic criteria of Ishii’s score estimated the highest prevalence [32] (50.8%); however, there were only two studies included in the subgroup based on Ishii’s score and SARC-F. The pooled results might be not reliable and need to be interpreted with caution. However, Li et al.’s [55] study verified that Ishii’s score had a high screening value among community-dwelling older adults. This result reminded us that the prevalence of sarcopenia among Chinese community-dwelling older adults may vary in terms of different diagnostic criteria. In addition, the cutoff values used in different diagnostic criteria also influenced the prevalence of sarcopenia. In **a et al.’s [43] study, this relative skeletal muscle mass index (RSMI) value was slightly higher among women, which may underestimate the prevalence of sarcopenia among older women. Nevertheless, 5 studies [25, 28, 30, 34, 40] used the EWGSOP as the diagnostic criteria, and those studies cutoff values of muscle mass and muscle strength were different from each other, which may influence the overall prevalence. For comparability among Asian community-dwelling older adults’ studies, it would be better to choose the AWGS, which has the same cut point value to diagnose sarcopenia, to diagnose the prevalence of sarcopenia in community-dwelling older adults.

The subgroup analysis of region or area showed that the prevalence of sarcopenia in North China (26.9%) was higher than that in South China (13.0%). To date, this is the first study to analyze the area difference in the prevalence of sarcopenia in China. Although Mao et al.’s [39] study separated their area into a northern city and a southern city, the result was inconsistent with our study. The high prevalence in North China in our meta-analysis may be due to one of the studies evaluating the prevalence in 80-year-old and old men living in Bei**g [30]. In addition, we inferred that this prevalence may be affected by the climate and diet patterns caused by geographical differences. Northern older adults may have less time to participate in outdoor physical activity due to the climate influence, and in their daily diet, cereals, eggs, beans and soy products were consumed more, while southern older adults consumed more aquatic products such as rice or fish [56]. They were naturally at greater risk of malnutrition and sarcopenia due to dietary preferences. Considering China as a multiethnic and large country, our findings should be further verified by future meta-analyses focusing on sarcopenia-associated risk factors, including diet structure, physical activity, climate, or diseases such as osteoarthritis, based on geography.

There are also limitations in this study. First, limited to the characteristics of individual studies and the situation of sarcopenia prevalence varying greatly from city to city, the heterogeneity among the included studies was strong. Second, among the 26 included studies, it only covered some province rather than the whole country, so the results cannot be generalized to reveal the overall prevalence of community-dwelling older adults in China. Third, due to the lack of a clear division of geographical location in the included studies, it was not possible to make a detailed subgroup analysis among urban and rural areas. Finally, some included studies did not provide needed information, such as the prevalence among different sexes and ages, so we could not analyze the source of heterogeneity.

Implications

The results of this meta-analysis revealed a serious situation of the overall prevalence of sarcopenia in Chinese community-dwelling older adults aged over 65 (17.4%), which should attract more attention from sports and public health departments. We also advise that future studies use BIA and AWGS to evaluate the prevalence of sarcopenia, which is more suitable for Chinese community-dwelling older adults. Considering that the prevalence of sarcopenia differs by region and area, the public health sectors need to take specific measures or publish targeted health-care policies to prevent the exacerbation of this situation.