Premium
Afternoon Spot Urine Osmolality as a Biomarker of Hydration in Free‐living Healthy Adults
Author(s) -
LEMETAIS Guillaume,
BOTTIN Jeanne,
POUPIN Marie,
JIMENEZ Liliana,
PERRIER Erica
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.967.4
Subject(s) - urine , morning , urine osmolality , medicine
Objective Previous research has highlighted links between fluid intake (FI), hydration parameters, and disease risk. Specifically, hydration markers in 24h urine samples respond quickly to a change in FI and have been linked to risk of CKD and lithiasis. However, 24h urine collection is burdensome, inconvenient, and time consuming. Spot urine collections would simplify daily hydration monitoring for researchers, clinicians, and individuals. Therefore, we assessed the equivalence of 24h and spot urine osmolality (24h Uosm; Spot Uosm) to determine whether a single spot may replace 24h collection. Methods 82 healthy adults with low to high habitual FI (50%M; age 23.6±2.9 y; BMI 22.2±1.5 kg/m 2 ) recorded all fluid consumed and collected individual voids over 24h. Uosm was measured on each void and on the pooled 24h sample. Equivalence between Spot and 24h Uosm was evaluated using the Two One‐Sided Test method (α=0.025). Results Spot Uosm from afternoon samples (14:00‐16:00; 16:00‐18:00; 18:00‐20:00) was equivalent to 24h Uosm whereas morning (08:00‐10:00; 10:00‐12:00) and midday (12:00‐14:00) spots tended to overestimate 24h Uosm. The mean [95% CI] difference between 24h and Spot Uosm was 287 [209;365] between 08:00‐10:00; 83 [12;154] between 10:00‐12:00; and 107 [58;157] between 12:00‐14:00. From 14:00‐16:00; 16:00‐18:00; and 18:00‐20:00, the mean difference was ‐25 [‐72;22]; 29 [‐35;92] and 12 [‐41;66]. Conclusion Afternoon Spot Uosm is equivalent to 24h Uosm. Thus, short, well‐timed urine collections may represent a convenient alternative to 24h samples, providing an easy way to monitor daily hydration in real‐life conditions. Afternoon Spot could also serve as an early warning signal to increase FI for maintaining 24h euhydration.