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Sex differences in the relation between 24h urine volume and osmolality (LB710)
Author(s) -
Perrier Erica,
Johnson Evan,
McKenzie Amy,
Ellis Lindsay,
Klein Alexis,
Armstrong Lawrence
Publication year - 2014
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.28.1_supplement.lb710
Subject(s) - urine , urine osmolality , medicine , body mass index , osmole , urine specific gravity , demography , endocrinology , physiology , sociology
Twenty‐four hour (24h) urinary hydration biomarkers have value in assessing hydration and disease risk. Specifically, highly concentrated urine and low urine volume increase relative risk for lithiasis and chronic kidney disease, respectively, and thus maintaining a high volume of dilute urine has been suggested as a simple preventive measure. Although there is a strong inverse relationship between 24h urine osmolality (U Osm ) and volume (U Vol ), sex differences in urine concentration have been reported. This suggests the possibility of sex differences in the U Osm :U Vol relationship which have not been fully explored. Our aim was to assess sex differences in the relationship between U Osm and U Vol , and to determine whether body mass may explain any observed differences. METHODS: 24h urine samples from 238 healthy American and French adults (50% men; age 28±6 y; BMI 22.9 ± 2.6 kg∙m ‐2 ) were analyzed for U Osm and U Vol . Sex differences in the U Vol :U Osm relationship were evaluated with linear regression. RESULTS: U Osm was higher in men at any given U Vol (whole model R 2 =0.67; β women mean±SE; ‐127±11 mOsm∙kg ‐1 ; p<.0001); however, the change in U Osm for a given change in U Vol was not different between sexes. Adjusting for body mass reduced the U Osm gap between men and women (β women ; ‐95±13 mOsm∙kg ‐1 ), yet sex remained as a significant predictor of U Osm and the fit of the model was unchanged (whole model R 2 =0.68; p<.0001). Although the distributions of both U Osm and U Vol show a slight positive skew; neither log‐ nor root‐ transformations substantially improved the fit of the model, nor the U Osm gap between men and women. CONCLUSIONS: At similar U Vol , men have higher U Osm than women. Though differences in body mass explain part of this sex gap, other factors likely play a role in the differential relationship of U Vol :U Osm in men and women.