Higher Body Mass Index in Hospitalized Older Patients Is Related to Higher Muscle Quality

Objectives This study aimed to examine the relationship between muscle mass, intramuscular adipose tissue, and body mass index (BMI) in older inpatients. Design Cross-sectional study. Setting Hospital-based study. Participants This study included 413 inpatients aged ≥ 65 years (186 men and 227 women). Measurements Muscle mass and intramuscular adipose tissue of the quadriceps were assessed by measuring the muscle thickness and echo intensity on ultrasound images. To examine the relationship between quadriceps thickness and echo intensity and BMI in total participants and each sex, the Kendall rank correlation coefficient was used. Multiple regression analysis was performed to examine whether BMI was independently and significantly related to the quadriceps thickness and echo intensity, even after adjusting for other variables for total participants and each sex. The independent variables in multiple regression analyses were BMI, age, disease, days from onset disease. Results The results of the correlation analyses showed that BMI was significantly related to the quadriceps thickness (total participants, τ = 0.431; men, τ = 0.491; women, τ = 0.388) and echo intensity (total participants, τ = −0.239; men, τ = −0.318; women, τ = −0.188). In the multiple regression analysis, BMI was independently and significantly associated with the quadriceps thickness (total participants, β = 0.535; men, β = 0.548; women, β = 0.519) and echo intensity (total participants, β = −0.287; men, β = −0.398; women, β = −0.210). Conclusion This study indicated that older inpatients with a higher BMI have greater muscle mass and less intramuscular adipose tissue of the quadriceps. These results suggested that a higher BMI in older inpatients is related to higher quadriceps muscle quality.