Dehydration and Population Health

Study Overview
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Brief Summary
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The primary aim of this study is to assess cardiovascular changes (blood pressure, heart rate, electrocardiogram/ECG) in response to mild fluid-restriction dehydration and subsequent rehydration in healthy young and old people. Secondary aims are to assess changes in body composition, mood, and hunger in response to mild dehydration and rehydration.

Detailed Description
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PARTICIPANTS: Forty healthy (no regular prescription medication use) male and females, between the ages of 18-70 years, will be recruited for this randomized-control cross-over study. Ideally, the investigators hope to recruit twenty younger (18-50) and twenty older (50-70) participants for this pilot study. All participants will be required to participate in two separate trials (a control and dehydration-rehydration trial, in randomized order), separated by at least a week. All menstruating females will be tested during the follicular phase of their menstrual cycle (i.e. within the first 14 days after the onset of the menstrual period). All participants will present to the lab in the evening for pre-testing and then in the morning for mid-testing/post-testing. With both pre-testing and mid-testing/post-testing each taking  90 minutes each, plus 12-hours of fluid deprivation or regular food/fluid intake overnight, the total time participating in collective study activities would be approximately 30-hours ( 15 hours per trial). PROCEDURES: For each of the two study trials, participants will come to the lab in the evening for pre-testing and then the following morning for mid-testing/post-testing (one trial). Hydration status will be assessed using blood (venipuncture), urine (spot sample), body weight, and thirst rating (100mm visual analogue scale). Cardiovascular variables will be assessed via heart rate, ECG, and blood pressure. Body composition will be measured using a dual energy x-ray absorptiometry (DXA) scan. Mood will be assessed using the Profile of Mood States (POMS) questionnaire. Once the participants present to the lab, pre-test blood, urine, body weight and composition, mood and thirst/sodium/hunger ratings will be obtained. Then, to enhance sweat water losses, each participant will be asked to walk on a motorized treadmill at a self-selected speed for 60-minutes. During the Dehydration-Rehydration trial, participants will be asked to refrain from ingesting any fluid (fluid restriction) for at least 12-hours overnight (i.e. from leaving the lab that evening until coming into the lab the next morning) to facilitate dehydration. After mid-testing, the participants will be allowed free access to water for a 60-minute rehydration period to quench their thirst (ad libitum drinking). At the end of this 60-minute rehydration period, post-test measures will be repeated. During the control trial, the participants can eat and drink as they please during the 12-hour overnight period.

Official Title
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Dehydration and Population Health

Conditions
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Dehydration (Physiology)

Intervention / Treatment
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* Other: Fluid restriction


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy (no regular prescription medication usage) Able to walk continuously on treadmill for 60 minutes Exclusion Criteria: Confirmed or suspected pregnancy Chronic medical condition Regular prescription medication use Inability to walk continuously walk on a treadmill for 60 minutes

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Fluid restriction|Study participants will refrain from drinking fluids overnight to facilitate 1-2% fluid loss from baseline|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cardiovascular changes | Changes in QRS waveforms will be assessed using electrocardiograms (ECG) before and after dehydration (fluid restriction) | change from baseline to dehydration (+13 hours) and then rehydration (+15 hours) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in perception of thirst and hunger | Thirst and hunger will be assessed on a VAS (visual analogue scale) before and after dehydration (fluid restriction) | change from baseline to dehydration (+13 hours) and then rehydration (+15 hours) | 
| Changes in body composition | Body composition (bone, lean, and fat mass) will be assessed using dual energy x-ray absorptiometry (DXA) scans before and after dehydration (fluid restriction) | change from baseline to dehydration (+13 hours) and then rehydration (+15 hours) | 
| Changes in mood | Mood will be assessed using the POMS (profile of mood states) survey before and after dehydration (fluid restriction) | change from baseline to dehydration (+13 hours) and then rehydration (+15 hours) |