Older Men Need to Stay Hydrated: Study

As we age, our ability to regulate body temperature and the ability to keep our bodies from becoming dehydrated declines. Hence a new study improves our understanding of the relation between temperature regulation and dehydration. The findings of the study are published in The Journal of Physiology. This research can help us better tailor strategies for managing body temperature regulation and hydration in older adults during heat exposure. For example, because of reductions in thirst and the ability to conserve body fluid, we may need more frequent reminders to drink water during work in the heat or during heatwaves, as we age.

Understanding the effects of dehydration on body temperature regulation came mainly from studies conducted in young adults.

Dehydration did not increase body temperature or decrease heat loss in older adults during exercise. Although it seems beneficial at first glance, this meant that the older adults did not try to adjust the sweat loss rate to prevent further dehydration. As a result, they encountered greater strain on the heart compared to younger men.

Previous studies indicate that as we age, our body reacts less efficiently to dehydration, and some have recommended that this is due to an impaired ability of the body to 'sense' increases in salt levels in the blood that would usually trigger thirst and drinking.

Since the decrease in sweat rate during dehydration is advantageous for decreasing fluid loss, experts at the Human and Environmental Physiology Research Unit assumed that a decreased sensitivity to elevated blood osmolality could also disclose the blunted effect of dehydration on heat loss and body temperature regulation among the elderly during exercise in the heat.

To test this hypothesis, the research group had young and older men perform the exercise in the heat. Before exercise, blood salt content was raised artificially by giving them infusions of saline.

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The volunteers performed the exercise in a device called a whole-body direct calorimeter, which accurately tracks the amount of heat lost from the entire body.

The study found that in contrast to young adults, the regulation of body temperature among older adults was not influenced by increases in the saltiness of the blood.

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While the study design allowed us to test the independent effect of osmolality on heat loss, the effect of decreased blood volume (termed hypovolemia) on sweating in older adults is currently unknown.

Source-Medindia