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Reduced osmotic thirst in healthy elderly men
P A Phillips1, M Bretherton, C I Johnston
1Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
The American Journal of Physiology
|July 1, 1991
Summary
Elderly men experience reduced thirst and drink less water when dehydrated due to hypertonicity. This is linked to lower thirst sensitivity in older adults, impacting hydration status.
Area of Science:
- Gerontology
- Physiology
- Hydration Science
Background:
- Aging is associated with altered physiological responses to dehydration and heat stress.
- Previous studies indicate reduced thirst in elderly men during water deprivation or heat stress.
- Water deprivation and heat stress induce both hypertonicity and reduced extracellular fluid volume.
Purpose of the Study:
- To investigate if elderly men exhibit reduced thirst in response to hypertonicity alone, without extracellular fluid volume depletion.
- To compare thirst perception and water intake between young and elderly men under controlled hypertonic conditions.
Main Methods:
- A double-blind, randomized crossover study involving healthy young (20-32 yr) and old (65-78 yr) men.
- Infusion of hypertonic (0.855 M) and isotonic (0.154 M) saline solutions to induce controlled hypertonicity.
- Measurement of thirst, water intake, plasma sodium, plasma volume, and plasma arginine vasopressin levels.
Main Results:
- Both young and old men reported increased thirst and water intake after hypertonic saline infusion compared to isotonic.
- Despite similar plasma sodium increases, elderly men reported significantly less thirst and consumed less water than young men.
- Reduced thirst in the elderly was primarily attributed to lower thirst sensitivity to hypertonicity, with a trend towards an increased thirst threshold.
Conclusions:
- Healthy elderly men exhibit reduced thirst and water intake compared to younger men when exposed to hypertonicity without significant extracellular fluid volume depletion.
- Age-related changes in thirst perception, specifically reduced sensitivity to hypertonicity, may contribute to inadequate fluid intake in older adults.
- These findings highlight the importance of monitoring hydration in the elderly, as their physiological responses to dehydration stimuli are altered.