Relationship Between Aging and Intramuscular Adipose Tissue in Older Inpatients.

Objective: Although older inpatients are known to develop various conditions, whether aging affects intramuscular adipose tissue in older inpatients remains unclear. In particular, an increase in intramuscular adipose tissue in persons aged ≥85 years has previously not been revealed in either older inpatients or community-dwelling older individuals. This study therefore aimed to examine whether aging affects intramuscular adipose tissue in older inpatients.

Design: Cross-sectional study.

Setting And Participants: This study was clinical-based and included 404 inpatients aged ≥65 years.

Methods: We divided the participants into the following age groups: 65-74 years (n = 63), 75-84 years (n = 171), and ≥85 years (n = 170). B-mode ultrasound imaging was performed, and the intramuscular adipose tissue of the quadriceps was assessed based on echo intensity. One-way analysis of variance and analysis of covariance were used to compare the echo intensity of the quadriceps between the 65-74-year, 75-84-year, and ≥85-year groups.

Results: The median (25th-75th percentile) ages of the 65-74-year group, 75-84-year group, and ≥85-year group were 70.0 (68.0-73.0), 80.0 (77.0-82.0), and 89.0 (87.0-91.0), respectively. In the one-way analysis of variance, the quadriceps echo intensity of the ≥85-year group was significantly higher than that of the 65-74-year and 75-84-year groups. In addition, the ≥85-year group had significantly higher quadriceps echo intensity than the 65-74-year group, even after adjusting for other confounding factors.

Conclusions And Implications: The current study revealed that intramuscular adipose tissue in older inpatients increases with age, and the levels of intramuscular adipose tissue of older inpatients aged ≥85 years is higher than those of older inpatients aged 65-74 years.