HYD: Assessing Hydration Status (2007)
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To identify whether saliva flow rate, saliva total protein concentration and saliva osmolality are sensitive non-invasive markers of whole body hydration status by comparing changes in these parameters with changes in body mass during progressive acute dehydration and rehydration.
Inclusion Criteria:
Healthy males, non-smokers and no significant oral, dental or systemic disease and were not taking any medication at the time of the study
Exclusion Criteria:
None
Description of Study Protocol:
Recruitment
Not described
Design
Study of sensitivity and specificity of a diagnostic test (prospective)
Blinding used (if applicable)
N/A
Intervention (if applicable)
- Subjects were given 30 ml/kg body mass of bottled water to drink between 9:00am and 9:00pm the day before the trial to ensure a euhydrated state.
- Dehydration protocol: In a exercise chamber of a dry bulb temperature of 30 oC and 70% relative humidity, subjects exercise 10 min of cycling on a stationary cycle ergometer at a power output corresponding to 60% maximal oxygen uptake. Subjects repeated the 10 min of exercise in the chamber followed by 5 min rest periods in the laboratory until progressive body mass loss of 1, 2 and 3% were reached. Subjects received no food or fluid during the dehydration protocol.
- Recovery: After exercise, subjects were given a volume of carbohydrate (CHO)-electrolyte solution (6% CHO and 25 mmol/l Na+) equivalent to 150% body mass loss to consume within 1 hour.
Statistical Analysis
- One-way repeated measures ANOVA (7 saliva collections) with significant differences assessed by applying the post hoc Tukey test.
- Pearson's correlation coefficient
Data Collection Summary:
Timing of Measurements
Saliva samples were collected at pre-exercise, 1, 2 and 3% body mass loss and then at 75, 135 and 195 min post-exercise.
Dependent Variables
- Saliva flow: Unstimulated whole saliva samples were collected over a 2 min period using pre-weighed salivette tubes
- Saliva volume: weighing the salivette tube immediately after collection to the nearest mg and saliva density was assumed to be 1.00 g/ml
- Saliva flow rate: volume of saliva/collection time
- Saliva total protein: Coomassie blue technique on a spectrophotometer using protein standards supplied with the kit
- Saliva osmolality: freezing point depression Osmometer (Model 3 MO, Advanced Instruments, Massachusetts)
Independent Variables
Dehydration; recovery protocols
Control Variables
None
Description of Actual Data Sample:
Initial N: 12
Attrition (final N): 12
Age: 21 ±1 years
Ethnicity: ND
Anthropometrics: Mean body weight = 76.2 kg
Location: UK
Summary of Results:
Changes in saliva flow rate, total protein concentration and osmolality during progressive acute dehydration and rehydration
Pre-excercise | 1.1% BML | 2.0% BML | 2.9% BML | 75 min Recovery | 195 min recovery | |
Saliva flow rate (ul/min) | 495 | 400 | 250* | 200*# | 550 | 550 |
Saliva total protein concentration(mg/ml) | 0.75 | 1.2* | 1.7*# | 1.75*# | 1.0 | 0.75 |
Saliva osmolality (mOsmo/kg) | 52 | 80* | 100*# | 100*# | 52 | 53 |
Values in the tables were estimated from figures.
*P<0.01, significantly different from pre-exercise
#P<0.01, significantly different from 1.1% BML (body mass loss)
- Saliva total protein concentration and osmolality correlated strongly with %BML during dehydration (mean r=0.97 and 0.94 respectively: P<0.01).
- Saliva flow rate negatively correlated with %BML during dehydration (mean r=-0.88: P<0.01).
Author Conclusion:
Changes in saliva total protein concentration, osmolality, and flow rate, are strongly associated with changes in body mass during progressive acute dehydration.
Funding Source:
University/Hospital: | University of Wales |
Reviewer Comments:
None
Quality Criteria Checklist: Primary Research
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Relevance Questions | |||
1. | Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) | N/A | |
2. | Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? | Yes | |
3. | Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? | Yes | |
4. | Is the intervention or procedure feasible? (NA for some epidemiological studies) | Yes | |
Validity Questions | |||
1. | Was the research question clearly stated? | Yes | |
1.1. | Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? | Yes | |
1.2. | Was (were) the outcome(s) [dependent variable(s)] clearly indicated? | Yes | |
1.3. | Were the target population and setting specified? | Yes | |
2. | Was the selection of study subjects/patients free from bias? | Yes | |
2.1. | Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? | Yes | |
2.2. | Were criteria applied equally to all study groups? | N/A | |
2.3. | Were health, demographics, and other characteristics of subjects described? | Yes | |
2.4. | Were the subjects/patients a representative sample of the relevant population? | Yes | |
3. | Were study groups comparable? | Yes | |
3.1. | Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) | N/A | |
3.2. | Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? | N/A | |
3.3. | Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) | N/A | |
3.4. | If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? | N/A | |
3.5. | If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) | N/A | |
3.6. | If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? | Yes | |
4. | Was method of handling withdrawals described? | Yes | |
4.1. | Were follow-up methods described and the same for all groups? | N/A | |
4.2. | Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) | N/A | |
4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | N/A | |
4.4. | Were reasons for withdrawals similar across groups? | N/A | |
4.5. | If diagnostic test, was decision to perform reference test not dependent on results of test under study? | Yes | |
5. | Was blinding used to prevent introduction of bias? | No | |
5.1. | In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? | N/A | |
5.2. | Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) | N/A | |
5.3. | In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? | N/A | |
5.4. | In case control study, was case definition explicit and case ascertainment not influenced by exposure status? | N/A | |
5.5. | In diagnostic study, were test results blinded to patient history and other test results? | No | |
6. | Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? | Yes | |
6.1. | In RCT or other intervention trial, were protocols described for all regimens studied? | N/A | |
6.2. | In observational study, were interventions, study settings, and clinicians/provider described? | N/A | |
6.3. | Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? | Yes | |
6.4. | Was the amount of exposure and, if relevant, subject/patient compliance measured? | N/A | |
6.5. | Were co-interventions (e.g., ancillary treatments, other therapies) described? | N/A | |
6.6. | Were extra or unplanned treatments described? | N/A | |
6.7. | Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? | N/A | |
6.8. | In diagnostic study, were details of test administration and replication sufficient? | Yes | |
7. | Were outcomes clearly defined and the measurements valid and reliable? | Yes | |
7.1. | Were primary and secondary endpoints described and relevant to the question? | Yes | |
7.2. | Were nutrition measures appropriate to question and outcomes of concern? | Yes | |
7.3. | Was the period of follow-up long enough for important outcome(s) to occur? | Yes | |
7.4. | Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? | Yes | |
7.5. | Was the measurement of effect at an appropriate level of precision? | Yes | |
7.6. | Were other factors accounted for (measured) that could affect outcomes? | Yes | |
7.7. | Were the measurements conducted consistently across groups? | Yes | |
8. | Was the statistical analysis appropriate for the study design and type of outcome indicators? | Yes | |
8.1. | Were statistical analyses adequately described and the results reported appropriately? | Yes | |
8.2. | Were correct statistical tests used and assumptions of test not violated? | Yes | |
8.3. | Were statistics reported with levels of significance and/or confidence intervals? | Yes | |
8.4. | Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? | N/A | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | N/A | |
8.6. | Was clinical significance as well as statistical significance reported? | Yes | |
8.7. | If negative findings, was a power calculation reported to address type 2 error? | N/A | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | Yes | |
9.1. | Is there a discussion of findings? | Yes | |
9.2. | Are biases and study limitations identified and discussed? | Yes | |
10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
10.1. | Were sources of funding and investigators' affiliations described? | Yes | |
10.2. | Was the study free from apparent conflict of interest? | Yes | |