Higher malnutrition risk in older inpatients who are referred to the department of rehabilitation is related to increase of intramuscular adipose tissue: A prospective study.

Background & Aims: A recent cross-sectional study reported that a higher intramuscular adipose tissue of the quadriceps is related to higher malnutrition risk in older inpatients. However, a longitudinal relationship between them in older inpatients remains unclear. This study aimed to examine the relationship between the malnutrition risk at hospital admission and change in quadriceps intramuscular adipose tissue induced during the hospital stay in older inpatients.

Methods: The inclusion criteria in this longitudinal study were older patients (aged ≥65 years) who were referred to the department of rehabilitation. Patients who died during a hospital stay, who underwent thigh amputation, and who had a hospital stay of <3 days or a lack of data were excluded from the study. Malnutrition risk at post-acute hospital admission was assessed using Geriatric Nutritional Risk Index (GNRI). Intramuscular adipose tissue and muscle mass of the quadriceps were assessed at hospital admission and discharge using echo intensity and muscle thickness on ultrasound images. The changes in quadriceps echo intensity and thickness were calculated by subtracting these baseline values from these values at discharge. Multiple regression analysis was performed to examine whether GNRI at admission is independently and significantly related to the quadriceps echo intensity and thickness at discharge and changes in quadriceps echo intensity and thickness. The independent variables were GNRI, age, sex, days from onset disease, disease, quadriceps echo intensity or thickness at admission, and change in quadriceps thickness.

Results: This study included 200 inpatients (median [interquartile range] age: 83.0 [77.0-88.0], 57.0% female). GNRI at admission was significantly and independently related to quadriceps echo intensity at discharge (β = -0.136, p = 0.008) and change in quadriceps echo intensity (β = -0.177, p = 0.008). In contrast, GNRI was not significantly and independently related to quadriceps thickness at discharge (β = 0.087, p = 0.158) and change in quadriceps thickness (β = 0.133, p = 0.158).

Conclusions: Our results suggest that a higher malnutrition risk at post-acute hospital admission in older inpatients is related to an increase of intramuscular adipose tissue of the quadriceps during the hospital stay. Malnutrition risk at hospital admission in older inpatients is considered to be a predictor for an increase of intramuscular adipose tissue of the quadriceps during a hospital stay.