#2057 Sex differences in bioimpedance-spectroscopy-derived fluid status and body composition of maintenance hemodialysis patients

Abstract

Abstract Background and Aims Bioimpedance-spectroscopy-(BIS)-derived estimates of fluid status and body composition are associated with mortality in patients undergoing maintenance hemodialysis (HD). Previously, thresholds for improved survival were identified for volume overload (VO, <2.5 L), VO relative to extracellular water (VO/ECW, <15%), lean tissue index (LTI, 15-20 kg/m2) and fat tissue index (4-15 kg/m2). However, these thresholds did not distinguish between sexes. Considering current efforts to untangle differences between male and female kidney disease patients, we aimed to analyze BIS data stratified by sex. Method We retrospectively evaluated pre-HD BIS measurements using the whole-body “Body Composition Monitor” device (Fresenius Medical Care). Measurements were conducted at the “Vienna Dialysis-Center”, a large tertiary dialysis center in Vienna, Austria. Continuous variables were described as medians and interquartile ranges and compared between sexes using Wilcoxon tests. Differences in proportions of males and females within the above-mentioned target ranges of body composition parameters were tested using Chi-Square tests and Fisher's exact tests. Results In November 2022, the Vienna Dialysis-Center cared for 304 patients, 159 of whom underwent BIS measurements. A total of 137 patients remained for analysis after excluding erroneous results (62% male, 38% female). The median [interquartile range] age among analyzed male and female patients was 60.0 years [48.0; 72.0] and 65.5 years [57.8; 75.3], and the median dialysis vintage was 28.9 months [12.1; 52.7] and 27.2 months [14.8; 61.9], respectively. VO (2.7 vs 1.9 L, p = 0.025), LTI (13.4 vs. 11 kg/m2, p < 0.001) and FTI (11.1 vs. 14.2 kg/m2, p = 0.036) differed significantly between males and females but VO/ECW did not (14.3 vs. 12%, p = 0.4). 27.1% of males (n = 23) were within 15-20 kg/m2 LTI compared to 7.7% of females (n = 4, p = 0.007). Differences in the proportions of male and female patients within optimal ranges of VO (43.5% vs. 61.5%, p = 0.062) and FTI (67.9% vs. 50.0%, p = 0.058) were close to reaching statistical significance. Conclusion We discovered relevant differences in fluid status and body composition among patients undergoing maintenance HD not only in absolute numbers, but also in the proportion of patients within the optimal range of LTI. Considering sex differences in body composition but (on average) equal mortality among HD patients, optimum target ranges of BIS measurements may differ between sexes. Our findings from this relatively small cohort call for large-scale sex-specific analyses of fluid status, body composition and outcomes in maintenance HD patients.