To the best of our knowledge, this is the first study to determine a combined index associated with the accumulation of CVD risk factors in obese patients among each of the obesity- (BMI, PBF, or WC) and sarcopenia-evaluated indices (SMI, HGS, or MQ), respectively. Among obese patients, sarcopenia was diagnosed in only one man (1.4%). This result is consistent with previous studies reporting that few obese individuals diagnosed with high BMI meet the conventional diagnostic criteria for sarcopenia [6, 10, 39, 40]. However, the prevalence of hypertension, diabetes, and dyslipidemia in these patients was high (Table 1), indicating that they are at a high risk for CVD. Therefore, we attempted to establish a diagnostic method for SO that reflects CVD risk. In this study, we provided evidence that classification using the combined index of WC and MQ reflects the accumulation of CVD risk factors in obese patients, regardless sex and age.
Many indices have been proposed for evaluating obesity. However, controversy remains on the obesity-evaluated index that best reflects the accumulation of CVD risk factors . In this study, WC was most highly associated with the accumulation of CVD risk factors as compared with BMI and PBF, regardless of sex and age (Table 2A). BMI has been widely used to determine the prevalence of obesity and various risks in populations. In addition, PBF is often used as a criterion for evaluating the magnitude of accumulation of adipose tissue. However, in recent years, the indices of abdominal obesity, mainly WC, have been shown to be more closely related to CVD and mortality than BMI and PBF are [42, 43], which is consistent with the findings of our study.
Many indices have been proposed to evaluate sarcopenia, including muscle mass, muscle strength, physical performance, and MQ, but it is also unclear which sarcopenia-evaluated index best reflects CVD risk accumulation. Cao et al reported that in patients with metabolic syndrome, low SMI may be an independent risk factor for atherosclerosis . In addition, low HGS has been reported to be associated with coronary artery calcification, CVD, and all-cause mortality [45-47] Our study demonstrated that MQ was most associated with the accumulation of CVD risk factors compared with SMI and HGS, regardless of sex and age (Table 2B). MQ was reported to be negatively associated with insulin resistance after adjusting for age, body fat, highly sensitive C-reactive protein levels, and physical activity level in adult obese women  and further that insulin resistance contributes to the development of atherosclerosis [49, 50], findings that are consistent with our results.
In this study, HGS was lower in group SO compared with group C (27.9 ± 9.0 vs. 33.0 ± 9.7 kg/m2, p < 0.05), whereas SMI was significantly higher in group SO compared with group C (8.32 ± 1.27 vs. 7.82 ± 1.03 kg/m2, p < 0.05; Table 3). Therefore, MQ calculated as the HGS (kg) divided by the muscle mass of the upper limbs was significantly lower in group SO compared with group C (5.71 ± 0.72 vs. 7.50 ± 0.71 kg/kg, p < 0.05; Table 3). Mesinovic et al reported that overweight and obese older adults with metabolic syndrome have larger muscle size but poor MQ . The lower MQ in group SO might be attributed to increased fat accumulation in the muscles [52, 53]; however, in this study, we did not measure MQ with imaging analysis, such as ultrasonography or computed tomography. Recently, the usefulness of phase angle as an indicator for MQ has been suggested [6, 54], and further studies on the increased fat accumulation in muscles are required in the future.
The combined index of WC and MQ was well associated with the accumulation of CVD risk factors in obese patients (Figure 3). To the best of our knowledge, there have been no reports on the diagnostic method for SO using a combined index of WC and MQ. Murai et al reported that patients with type 2 diabetes who had both visceral fat accumulation and low MQ were more affected with CVD . The effectiveness of the combined index of WC and MQ as a relevant indicator of accumulation of CVD risk factors in obese patients requires further investigation.
The use of multiple medications per day is common with aging. Many drugs taken regularly for diseases may interact with some mechanisms that can alter the balance between protein synthesis and degradation , and researchers have reported that polypharmacy is associated with sarcopenia . In this study, diuretics and biguanide (BG) were used significantly more often in group SO compared with group S and group C, respectively (p < 0.05, p < 0.05; Supplementary Table S1). The use of diuretics, particularly loop diuretics, has been suggested as a risk factor of sarcopenia . On the other hand, BG improves insulin resistance and may inhibit the progression of sarcopenia . Unfortunately, we did not assess insulin resistance in this study, but it has been reported that patients with SO are in an insulin-resistant state [2, 4]. It is likely that BG was provided for insulin resistance in group SO in this study. The effects of BG on muscle remain to be elucidated.
The present study had several limitations that warrant mention. First, our study used a cross-sectional design. Thus, we could investigate only the associations between the combined index of WC and MQ and the accumulation of CVD risk factors. Second, because of the hospital-based design of the study, there may be bias among the study participants, which could limit the generalization of the study results. Third, the cutoff values for both WC and MQ were not clear. However, we were able to diagnose SO using the median of WC and MQ indices as cutoff values, which reflected well the accumulation of CVD risk factors. To resolve these limitations, larger cohort and prospective studies including various populations are needed in the future.
In conclusion, our study demonstrated that the obesity-evaluated index, WC, and the sarcopenia-evaluated index, MQ, were most closely associated with the accumulation of CVD risk factors in obese patients, respectively. Furthermore, classification by the combined index of WC and MQ reflects the accumulation of CVD risk factors in obese patients, regardless of sex and age.