Document Type

Article

Publication Date

2024

DOI

10.1002/ajhb.24139

Publication Title

American Journal of Human Biology

Volume

Article in Press

Pages

1-10

Abstract

Objective

We aimed to evaluate how urine specific gravity (USG) and rates of supposed hypohydration vary by race/ethnicity, and to examine how adjustment for several important factors impacts estimated USG.

Methods

Using the National Health and Nutrition Examination Survey, this cross‐sectional study evaluated a total of 4195 (2098 female, 2097 male) Americans and categorized them as supposedly hypohydrated (USG≥1.020) or not using spot urine samples. USG and prevalence of supposed hypohydration were compared across racial/ethnic groups, separately by gender. The analyses considered the impact of urine creatinine, body composition, age, dietary nutrients, and physical activity.

Results

Differences in supposed hypohydration prevalence were observed by race/ethnicity in men (p = .030) and women (p < .001). In unadjusted models, Black women's USG (1.0189) was higher (p < .05) than all the other race/ethnicity groups' USG (1.0142–1.0171). In men, Blacks' USG (1.0197) was higher (p < .05) than the USG of Whites (1.0177) and other/multi‐racial (1.0176) but not Mexican Americans (1.0196) or other Hispanics (1.0192). Adjustments for age, arm circumference, nutrients (protein, sodium, potassium, and moisture), and physical activity minimally influenced USG estimates. Further adjustment for urine creatinine lowered USG for Black women and men by 0.003 and 0.0023, respectively, with no notable lowering of USG in the other races/ethnicities. Supplemental analyses matching Whites and Blacks on age, moisture intake, and poverty‐to‐income ratio confirmed racial differences in urine creatinine and USG, though the effects were most pronounced in women.

Conclusions

Using a USG≥1.020 to identify hypohydration in all races/ethnicities may be inappropriate due to, among other factors, differences in urinary creatinine.

Rights

© 2024 The Authors.

This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Data Availability

Article states: "The data that support the findings of this study are available from the corresponding author upon reasonable request."

Original Publication Citation

Winter, I. P., Ferguson, B. K., & Wilson, P. B. (2024). Associations between urine specific gravity and race/ethnicity at the population level: Implications for hydration status categorization. American Journal of Human Biology, e24139. https://doi.org/10.1002/ajhb.24139

ORCID

0000-0003-4052-5023 (Wilson)

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