Abstract: Objective:To investigated the gender differences and dynamic changes of the sarcopenia index （ SI） in patients undergoing  peritoneal  dialysis  （ PD）  and  explored  its  clinical  significance.     Methodology: This  single⁃center retrospective study followed adult patients with PD who met the center-s criteria until July 2024. The primary endpoint was all⁃cause mortality. The SI was calculated using the concentrations of serum creatinine （ Cr）  and cystatin C （ CysC）  during the same period， employing the formulas Cr / CysC and Cr×eGFRcys， respectively. First， we analyzed gender differences in the SI values. Subsequently， we  utilized  the  Cox  proportional  hazards  regression  model  and  the  competing  risks  model  to examine the  relationship  between  the  SI  and  all⁃cause  mortality.  Finally，  we  discussed  the  dynamic  changes  of  the  SI following dialysis.    Results:A  total  of  1034  patients  with  PD  were  included  in  the  study，  comprising  563  men  and  471 women. The average age at baseline  was 45.1± 14.2  years， with  a  total  KT / V  of 2.03± 0.64.  The  average  levels  of  Cr / CysC （ 2.03±0.67 vs  1.81 ± 0.59）  and  Cr × eGFRcys  （ 94.2 ± 33.9  vs  86.2 ± 31.5）  in  male  patients  were  significantly higher than those  in  female  patients  （ both  P  <  0.001），  demonstrating  a  very  significant  correlation  between  them  （ r > 0.95， P<0.001）. Using the Cox proportional hazards regression model to analyze continuous and categorical variables for Cr / CysC， it was found that patients with higher Cr / CysC levels had better survival outcomes compared to those with lower levels. However， sex  was  not  statistically  significant  in  this  analysis，  although  the  difference  remained  significant  among male patients. Additionally， in  the  competing  risks  model  analysis，  the  disparity  in  Cr / CysC  levels  continued  to  show  a significant relationship with the survival rate  of  male  patients.  Finally， the  average  Cr / CysC  level  tended  to  decrease  and then increase in the first  year  after  starting  dialysis.    Conclusion:Gender  differences  existed  in  the  SI  levels  of  patients with PD， with male patients exhibiting significantly higher average levels than their female counterparts.  Additionally， the SI level served as  an  independent  predictor  of  prognosis  in  PD  patients，  particularly  among  males.  The  average  SI  level tended to decrease and then increase in the first year after starting dialysis.

Key words: peritoneal dialysis, sarcopenia index, serum creatinine / cystatin C ratio, all?cause mortality