Sex Differences in Age-Related Changes in the Extracellular Water-to-Total Body Water Ratio among Community-Dwelling Individuals.

Abstract

Introduction: The European Working Group on Sarcopenia in Older People 2 revised its diagnostic criteria for sarcopenia, highlighting the importance of evaluating not only skeletal muscle mass but also muscle quality. Recently, the extracellular water-to-total body water ratio (ECW/TBW) has gained attention as an indicator of muscle quality. The aim of this study was to investigate the sex differences in the effect of aging on ECW/TBW in community-dwelling individuals.

Methods: This cross-sectional study was conducted among community-dwelling males and females (aged ≥20 years). A total of 824 participants (345 males, 479 females) were included. ECW/TBW was measured using bioelectrical impedance analysis. Associations between age and ECW/TBW were analyzed separately for males and females using Spearman's correlation coefficient. Participants were categorized into three age groups: 20-39 years, 40-64 years, and ≥65 years. Among males (n = 345), the age groups 20-39, 40-64, and ≥ 65 years comprised 124, 128, and 93 participants, respectively. Among females (n = 479), the corresponding numbers were 94, 164, and 221 participants, respectively. The Kruskal-Wallis test was used to compare ECW/TBW among the three groups for both males and females. Bonferroni's post hoc test was used to determine the significance when the main effect was confirmed in the Kruskal-Wallis test. In addition, a two-way analysis of variance was performed on ECW/TBW with age group and sex as factors.

Results: Correlation analyses revealed a significant positive association between age and ECW/TBW in both males (ρ = 0.733, p < 0.001) and females (ρ = 0.684, p < 0.001). For both males and females, a main effect of age on ECW/TBW was observed among the three groups. In addition, for both males and females, the ECW/TBW in the ≥65-year group was significantly higher than in the 20-39 and 40-64-year groups. ECW/TBW showed a significant interaction between age group and sex (p < 0.001).

Conclusions: The results of this study indicated that age is positively related to ECW/TBW in community-dwelling males and females. Additionally, the influence of aging on ECW/TBW was more pronounced in males than in females. Based on our findings, assessing ECW/TBW is important for capturing age-related changes.