Skip to main content

Observations on saliva osmolality during progressive dehydration and partial rehydration

Journal Article


Abstract


  • A need exists to identify dehydrated individuals under stressful settings beyond the laboratory. A predictive index based on changes in saliva osmolality has been proposed, and its efficacy and sensitivity was appraised across mass (water) losses from 1 to 7%. Twelve euhydrated males [serum osmolality: 286.1 mOsm kg -1 H 2O (SD 4.3)] completed three exercise- and heat-induced dehydration trials (35.6°C, 56% relative humidity): 7% dehydration (6.15 h), 3% dehydration (with 60% fluid replacement: 2.37 h), repeat 7% dehydration (5.27 h). Expectorated saliva osmolality, measured at baseline and at each 1% mass change, was used to predict instantaneous hydration state relative to mass losses of 3 and 6%. Saliva osmolality increased linearly with dehydration, although its basal osmolality and its rate of change varied among and within subjects across trials. Receiver operating characteristic curves indicated a good predictive power for saliva osmolality when used with two, single-threshold cutoffs to differentiate between hydrated and dehydrated individuals (area under curve: 3% cutoff = 0.868, 6% cutoff = 0.831). However, when analysed using a double-threshold detection technique (3 and 6%), as might be used in a field-based monitor, <50% of the osmolality data could correctly identify individuals who exceeded 3% dehydration. Indeed, within the 3-6% dehydration range, its sensitivity was 64%, while beyond 6% dehydration, this fell to 42%. Therefore, while expectorated saliva osmolality tracked mass losses within individuals, its large intra- and inter-individual variability limited its predictive power and sensitivity, rendering its utility questionable within a universal dehydration monitor. © 2012 Springer-Verlag.

UOW Authors


  •   Taylor, Nigel A.S.. (external author)
  •   van den Heuvel, Anne (external author)
  •   Kerry, Pete (external author)
  •   McGhee, Sheena S. (external author)
  •   Peoples, Gregory
  •   Brown, Marc
  •   Patterson, Mark J. (external author)

Publication Date


  • 2012

Citation


  • Taylor, N. A.S.., van den Heuvel, A., Kerry, P., McGhee, S., Peoples, G. E., Brown, M. & Patterson, M. J. (2012). Observations on saliva osmolality during progressive dehydration and partial rehydration. European Journal of Applied Physiology, 112 (9), 3227-3237.

Scopus Eid


  • 2-s2.0-84865371087

Ro Metadata Url


  • http://ro.uow.edu.au/hbspapers/3067

Number Of Pages


  • 10

Start Page


  • 3227

End Page


  • 3237

Volume


  • 112

Issue


  • 9

Abstract


  • A need exists to identify dehydrated individuals under stressful settings beyond the laboratory. A predictive index based on changes in saliva osmolality has been proposed, and its efficacy and sensitivity was appraised across mass (water) losses from 1 to 7%. Twelve euhydrated males [serum osmolality: 286.1 mOsm kg -1 H 2O (SD 4.3)] completed three exercise- and heat-induced dehydration trials (35.6°C, 56% relative humidity): 7% dehydration (6.15 h), 3% dehydration (with 60% fluid replacement: 2.37 h), repeat 7% dehydration (5.27 h). Expectorated saliva osmolality, measured at baseline and at each 1% mass change, was used to predict instantaneous hydration state relative to mass losses of 3 and 6%. Saliva osmolality increased linearly with dehydration, although its basal osmolality and its rate of change varied among and within subjects across trials. Receiver operating characteristic curves indicated a good predictive power for saliva osmolality when used with two, single-threshold cutoffs to differentiate between hydrated and dehydrated individuals (area under curve: 3% cutoff = 0.868, 6% cutoff = 0.831). However, when analysed using a double-threshold detection technique (3 and 6%), as might be used in a field-based monitor, <50% of the osmolality data could correctly identify individuals who exceeded 3% dehydration. Indeed, within the 3-6% dehydration range, its sensitivity was 64%, while beyond 6% dehydration, this fell to 42%. Therefore, while expectorated saliva osmolality tracked mass losses within individuals, its large intra- and inter-individual variability limited its predictive power and sensitivity, rendering its utility questionable within a universal dehydration monitor. © 2012 Springer-Verlag.

UOW Authors


  •   Taylor, Nigel A.S.. (external author)
  •   van den Heuvel, Anne (external author)
  •   Kerry, Pete (external author)
  •   McGhee, Sheena S. (external author)
  •   Peoples, Gregory
  •   Brown, Marc
  •   Patterson, Mark J. (external author)

Publication Date


  • 2012

Citation


  • Taylor, N. A.S.., van den Heuvel, A., Kerry, P., McGhee, S., Peoples, G. E., Brown, M. & Patterson, M. J. (2012). Observations on saliva osmolality during progressive dehydration and partial rehydration. European Journal of Applied Physiology, 112 (9), 3227-3237.

Scopus Eid


  • 2-s2.0-84865371087

Ro Metadata Url


  • http://ro.uow.edu.au/hbspapers/3067

Number Of Pages


  • 10

Start Page


  • 3227

End Page


  • 3237

Volume


  • 112

Issue


  • 9