Loss of body weight in older inpatients with severely low BMI according to the GLIM criteria is related to muscle mass loss of the quadriceps

Abstract Background & Aims Body weight is one of the essential indicators of nutritional status, and body weight management is vital in nutritional care. In addition, low body mass index (BMI) was included as phenotypic criterion in the Global Leadership Initiative on Malnutrition (GLIM) criteria. Furthermore, low BMI has been used in grading the severity of malnutrition (moderate or severe malnutrition) in the GLIM criteria. A recent cross-sectional study reported that muscle mass of the quadriceps in older inpatients with severely low BMI is less than those of older inpatients with moderately low BMI and normal BMI. However, the longitudinal relationship between muscle mass of the quadriceps and body weight in older inpatients with severely low BMI remains unclear. This study aimed to examine the longitudinal relationship between muscle mass of the quadriceps and body weight in older inpatients with severely low body mass index (BMI) according to the Global Leadership Initiative on Malnutrition (GLIM) criteria. Methods This retrospective cohort study included 179 older inpatients (aged ≥ 70 years) (median [IQR] age: 84.0 [79.0–89.0]). In accordance to the cut-off value of a low BMI for patients aged ≥ 70 years in the Asian population according to the GLIM criteria, the participants were divided into the following three groups: the severely low BMI group (< 17.8 kg/m 2 ) (n = 47), moderately low BMI group (≥ 17.8 to < 20.0 kg/m 2 ) (n = 38), and normal BMI group (≥ 20.0 kg/m 2 ) (n = 94). The primary outcomes were changes in muscle mass of the quadriceps and body weight. Muscle mass of the quadriceps was examined using ultrasound images (i.e., quadriceps thickness). The changes in quadriceps thickness and body weight were calculated by subtracting the quadriceps thickness and body weight at admission from those values at discharge. Multiple linear regression analysis adjusting for confounding factors was used to determine whether the change in body weight was independently and significantly related to change in quadriceps thickness in the severely low BMI, moderately low BMI, and normal BMI groups. Results The means (SD) of the change in quadriceps thickness of the severely low BMI group, moderately low BMI group, and normal BMI group were 0.0 ± 0.3 cm, 0.1 ± 0.3 cm, and 0.1 ± 0.5 cm, respectively. The means of the change in body weight in those groups were 0.4 ± 2.8 kg, − 1.1 ± 2.7 kg, and − 1.3 ± 4.3 kg, respectively. In the severely low BMI group, change in body weight (β = 0.29, p = 0.033) and quadriceps thickness at admission (β = −0.57, p < 0.001) were significantly and independently related to change in quadriceps thickness (R 2 = 0.588, f 2 = 1.427, statistical power = 0.999). In the moderately low BMI and normal BMI groups, there were no factors which were significantly and independently related to change in quadriceps thickness. Conclusions The results of this study suggest that loss of body weight in older inpatients with severely low BMI according to the GLIM criteria is related to loss of muscle mass of the quadriceps. These results imply the importance of body weight management for older inpatients with severely low BMI perspective from muscle mass of the quadriceps.