Mediation effects of age, intramuscular adipose tissue index and serum albumin on survival status in initial dialysis patients.

Background: To explore the associations of age, intramuscular adipose tissue index (IATI), and serum albumin with survival status in initial dialysis patients and the mediating effects.

Methods: Totally 1,044 Chinese initial dialysis patients from four hospitals (2014-2020) were eventually enrolled and followed up to December 31, 2022 or until death in this retrospective cohort study. IATI was defined as the ratio of low attenuation muscle density to skeletal muscle density assessed by CT at the first lumbar vertebra level. Multivariate Cox regression and two-piecewise Cox proportional hazards models were used to determine the risk factors for all-cause mortality and to perform stratified analysis. Mediation analysis was conducted to identify mediators.

Results: High IATI, age > 60 years, and low serum albumin were significant independent risk factors for all-cause mortality. The association between IATI and all-cause mortality remained significant in female patients, and those with low neutrophil/lymphocyte ratios, or without coronary heart disease. When age and IATI were categorical variables, age had a significant indirect effect on all-cause mortality (0.015) and survival time (-1.262) via IATI, while IATI indirectly influenced all-cause mortality through serum albumin (0.012).

Conclusions: Age > 60 years and high IATI are risk factors for all-cause mortality while serum albumin is protective in initial dialysis patients. The relationship between age and survival status may be mediated by IATI, while the effect of IATI on all-cause mortality may be mediated by serum albumin.