Characterizing Seven Day 24-hour Urinary Hydration Markers In College-aged Men And Women

Abstract

Maintaining a day-to-day state of euhydration is advantageous for acute and long-term health. However, little data exists examining 24h hydration status in free-living emerging adults (18 – 25y). PURPOSE: Thus, the purpose of this study was to assess 24h urinary hydration markers across 7 days in male and female college students. METHODS: Eighteen participants (male, n=11; female, n=7; mean±SD; age, 23±3y; height, 164.6±15.3cm, body mass, 73.48±15.86kg; body fat, 19.4±9.4%) provided a 24-hour urine sample on 7 consecutive days. Measures of 24h urine volume (UVOL), urine osmolality (UOSM), urine specific gravity (USG), and urine color (UCOL) were assessed each day. Differences in 24h urinary hydration markers between weekdays and weekend days were assessed. RESULTS: Across 7 days, mean UVOL, UOSM, USG, and UCOL was 1.59±0.89 L, 628±284 mOsm•kg-1, 1.020±0.007, 3.8±1.6, respectively. There were no differences (all p > 0.05) between weekday and weekend days for mean UVOL (1.61±0.82 vs. 1.56±0.72 L) , UOSM (626±270 vs. 627±235 mOsm•kg-1), USG (1.020±0.007 vs. 1.020±0.006), and UCOL (3.8±1.4 vs. 3.8±1.5), respectively. Mean weekend day measures of UVOL (adj R2 = 0.507, p=0.001), UOSM (adj R2 = 0.547, p<0.001), USG (adj R2 = 0.551, p<0.001), and UCOL (adj R2 = 0.608, p<0.001) were all significantly associated with mean weekday measures. CONCLUSION: Our results suggest that, in this sample population of college students, individuals tended to have stable 24-hour urinary hydration measures across weekdays and weekend days. Despite finding relative stability in 24 hour urinary hydration markers across a week, we are unable to discuss factors associated with day-to-day variation in these measures. Integrating other factors such as previous personal and family medical history, physical activity, dietary intake, body composition, racial/ethnic background, and socioeconomic status may further elucidate variations in day-to-day hydration status and the role hydration plays in emerging adults on health.