A new research confirms that the body signals that help younger men stay hydrated may be absent in older men.
Smart thermostats on our hypothalamus have nothing. This is the gland that helps us maintain the temperature of a healthy body.
The hypothalamus causes our skin to generate sweat when we get too hot, which cools us off when it evaporates. We then become thirsty, and we should drink to substitute the water that we abandoned through sweating.
However, we can become dehydrated if we sweat too much or do not drink water to replenish our fluids.
We lose the capacity to cool ourselves with sweat without adequate water in the body, and the body will overheat. This raises our risk of suffering heatstroke and other harm to our bodies related to heat.
As we age, our temperature control system’s performance declines. While most of the research on the effects of dehydration focuses on young adults, its role in the health of older adults is explored in a new study in The Journal of Physiology.
Older adults may not feel as thirsty as young people, and when they work or exercise and when the weather is hot, they should take care to hydrate.
Dehydration changes as we age
The paradoxical risk associated with dehydration later in life was investigated by researchers from the Human and Environmental Physiology Research Unit at the University of Ottawa in Canada.
On the one hand, dehydration in older adults during exercise does not contribute as readily to an increase in body temperature by minimizing heat loss as it does in younger people.
Although this may seem to be a good thing, the absence of sweat and thirst means the person loses valuable insights that suggest that it is time to rehydrate.
Dehydration in older adults can continue and quietly increase to dangerous levels without drinking enough water.
Blood salinity
The reason that older adults feel less thirsty is due to a decreased capacity to detect and respond to the amount of salt in their blood, scientists have suggested.
The body of a younger adult reacts with feelings of thirst as the balance between water and salt in the blood tips against salinity.
The researchers wondered if the same decreased ability to regulate blood salinity, or “osmolality,” that decreases thirst sensations, may also be the driving force behind older adults’ less severe response to dehydration.
Ten younger men (18-30 years) and 10 older men (54-67 years) were involved in heat stress experiments for exercise. For 24 hours before each session, the researchers asked them to abstain from drinking alcohol and participating in strenuous exercise. The night prior to the experiments, they also asked them to drink 500 milliliters of water.
The men took part in two workout sessions a week apart following the screening. At the start of each exercise session , the participants received an intravenous saline solution to increase blood osmolality before entering a heated, whole-body direct-air calorimeter for 1 hour of stationary cycling.
The calorimeter assessed the whole-body evaporative and dry heat loss of the participants, and other instruments monitored a variety of body temperature and heat loss rate indicators.
Analysis of the results showed a substantial gap between younger and older men in the control of body temperature.
The researchers found that an rise in blood salinity for older men did not cause the body’s reactions to dehydration, as it did for younger men.
An incomplete picture
To help scientists gain a full understanding of heat control in older adults, further research would be required.
“While our research 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,” as first study author Robert Meade says.
Since the study studied the impact of blood osmolality without any known chronic conditions in physically active participants, it is unknown whether or not the same result will apply to older adults with common age-related conditions such as type 2 diabetes.
However, Meade concludes:
“Given that common age-related chronic health conditions such as type 2 diabetes are associated with less efficient regulation of body temperature and hydration status, future research should be conducted to see whether our findings translate to or are exaggerated in those populations.”
