Sex Differences In The Accuracy Of WUT (Weight, Urine Color, Thirst) Diagrams Assessing Hydration Status

PURPOSE: To observe sex differences in the accuracy of WUT (Weight, Urine Color, Thirst) diagrams assessing hydration status. METHODS: 8 males [M] (age: 21 ± 3; mass: 76.3 ± 15.6 kg) and 5 females [F] (age: 22 ± 2; mass: 60.5 ± 13.6 kg) visited the laboratory twice a day (morning and afternoon) for six days as free-living for the first three consecutive days and euhydrated (urine specific gravity (USG) < 1.020) for the last three consecutive days. During each visit, thirst perception (TP), body mass (BM), USG, urine osmolality (UOSM), urine color (UCOL), and plasma osmolality (POSM) were collected. Values of USG >1.020, UOSM> 700, and POSM> 290 indicated dehydration. TP >5, UCOL > 5, and %BM Loss >1% values were used as dehydration thresholds for WUT scores. Total WUT score (0-3) was determined by the total amount of respective dehydration markers identified. One-way ANOVA was used to analyze differences in POSM, UOSM, and USG between the different WUT scores for both sexes. Receiver operating characteristics analysis was used to calculate sensitivity (SENS) and specificity (SPEC) identifying dehydration or euhydration with WUT scores. RESULTS: For POSM, WUT3 (M: 291 ± 5; F: 286 ± 0 mOsmol), WUT2 (289 ± 6; 286 ± 7), WUT1 (286 ± 5; 286 ± 6), and WUT0 (289 ± 5; 285 ± 7) were not different between sexes (p > .05). For USG, WUT3 (1.022 ± .004; 1.020 ± .000), WUT2 (1.019 ± .008; 1.020 ± .007), WUT1 (1.015 ± .006; 1.0100 ± .005), and WUT0 (1.010 ± .006; 1.008 ± .006) were not different between sexes (p > .05). For UOSM, WUT3 (819 ± 147; 744 ± .000 mOsmol), WUT2 (679 ± 244; 788 ± 261), WUT1 (521 ± 266; 461 ± 212), and WUT0 (383 ± 212; 322 ± 203) were not different between sexes (p > .05). For POSM, WUT2SPEC was higher in M (WUT2Mspec, .860) than F (WUT2Fspec, .786) while WUT3, WUT1, and WUT0 were similar between sexes (WUT3Mspec, .965; WUT3Fspec, .976; WUT1Mspec, .526; WUT1Fspec, .380). For USG, WUT2SENS was higher in F (WUT2Fsens, .889) than M (WUT2Msens, .571) while WUT3, WUT1, and WUT0 were similar between sexes (WUT3Msens, .238; WUT3Fsens, .111; WUT1Msens, .905; WUT1Fsens, .889). For UOSM, SPEC and SENS were similar between sexes for each WUT score. CONCLUSION: There are no sex differences in USG, UOSM, and POSM between WUT0-3. However, based on SPEC and SENS, WUT3 and WUT0 can detect hydration status in both sexes. WUT2 might be used to detect hydration status only for females.