0823 Age-Related Changes in Nocturnal Urine Composition

Abstract Introduction In humans sleeping nocturnally, nocturnal polyuria (NP) refers to high rate of overnight urine production. NP is a heterogeneous condition that may reflect both free water and/or sodium diuresis, but the influence of age on differential fluid handling remains poorly understood. This study examined diuresis rate, sodium clearance, and free water clearance (FWC) by age, time of day (nighttime vs. daytime) and NP status (positive/negative) in subjects under entrained conditions sleeping nocturnally. Methods Convenience samples (age range 18-91; 82 men, 148 women) recruited from a urology ambulatory care unit (n=135) or continence clinic (n=95) collected 8 urine samples at 3-hour intervals over a single 24-hr period. Three separate mixed linear models were constructed for diuresis rate, sodium clearance, and FWC using four predictors: NP status (present [>90mL/h] vs. absent), time of day (night = 0100, 0400, 0700), age (as a continuous measure), and study source. Results Subjects with NP experienced both higher nighttime vs. daytime diuresis rate (1.89 vs. 1.44 mL/min, p