Age and Gender-Related Trajectories of Urine Osmolality in a Large-Scale Population Study: Physiological Mechanisms and Clinical Implications.
TL;DR
A universal pattern of age-related decline in renal function is confirmed, likely driven by renal senescence and hormonal shifts, and a significant sexual dimorphism attributable to the influence of gender hormones on renal water and solute handling is revealed.
Abstract
Background
To delineate the lifelong trajectories of urine osmolality (Uosm), a primary indicator of renal concentrating capacity, and to investigate the influence of age and gender in a large, non-Western population. This study aims to establish population-specific reference data and explore the underlying physiological mechanisms and clinical implications of observed trends.
Methods
This cross-sectional study analyzed retrospective data from 128,889 individuals (65,625 males, 63,264 females), aged 20 to 89 years, who underwent routine physical examinations at a single center in Shaoxing, China, between 2019 and 2022. First-morning urine osmolality was estimated using the electrical conductivity method on a Sysmex UF-5000 analyzer. Data were stratified by gender and 10-year age increments. Statistical analyses included independent t-tests and one-way ANOVA to compare mean Uosm values across groups.
Results
A profound and persistent sexual dimorphism was observed, with males exhibiting significantly higher mean Uosm than females across all age groups (p < 0.001). Overall mean Uosm was 657 mOsm/kg H2O (95% CI: 655 - 659) for males and 598 mOsm/kg H2O (95% CI: 596 - 600) for females. For both genders, Uosm peaked in the 20 - 30 year age group and demonstrated a progressive, inexorable decline with advancing age. This decline was gradual until age 70, after which it accelerated markedly. The absolute difference in Uosm between males and females was greatest in young adulthood and attenuated significantly in later life, with the narrowest gap observed in the > 70 - 80 year age group.
Conclusions
This large-scale study provides the first high-resolution demographic map of renal concentrating capacity in an East Asian population, revealing distinct age- and gender-specific trajectories. The findings confirm a universal pattern of age-related decline in renal function, likely driven by renal senescence and hormonal shifts, and a significant sexual dimorphism attributable to the influence of gender hormones on renal water and solute handling. The data highlight specific vulnerabilities - an endemic risk of suboptimal hydration predisposing to urolithiasis in men and a heightened risk of dehydration in the elderly - underscoring the need for age- and gender-stratified approaches in clinical nephrology, geriatric medicine, and public health.