By Mari Hopper, PhD

Assistant Professor of Biology

Pott College of Science and Engineering

University of Southern Indiana

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The long hot days of summer are upon us. Although many welcome the increase in ambient temperature, higher temperatures mean increased health risk for older adults. Epidemiological studies indicate most of the deaths due to hyperthermia (elevated body temperature due to failed thermoregulation) occur in elderly individuals.

The ability to thermoregulate, or control body temperature, is essential for normal body function and even survival. Normal body temperature is held relatively constant at 98.6 degrees through complex multi-faceted control systems. Due to a number of changes in the body as we age, our ability to maintain body temperature becomes more difficult. Although the reasons are not completely understood, age related changes compromise one’s ability to sense temperature changes and respond appropriately.

Most body heat is generated as a by-product of metabolism, the body’s internal activities. A steady decline in metabolic rate is a normal consequence of aging. Studies with lemurs (nonhuman primate with aging processes similar to humans) conducted by Aujard and colleagues (2005) concluded that aging animals select higher ambient temperatures than younger adults to compensate for the decline in metabolic rate. Self-placement into a warm environment coupled with suboptimal ability to respond to even a moderate shift in temperature of the environment may place an individual at risk for heat stress.

Under heat stress conditions, humans rely on a number of cooling mechanisms including increased sweat production, redistribution of blood flow to the skin, and an increase in pumping action of the heart to distribute blood flow for cooling. Compared to young adults, older individuals find it much more difficult to cope with water loss experienced as a result of sweating. Reduction in the plasma volume, or the water portion of the blood, affects circulatory dynamics and the ability to distribute blood to the skin for cooling. The individual’s heart may be overworked as it attempts to pump blood to the skin in effort to release heat via convection from the skin to the environment. The extra work of the heart is often the cause of death (not hyperthermia). The ability to adequately compensate for changes in body temperature may also be negatively impacted by disease and nutritional status.

Compounding the problem is the fact that older individuals may also experience inadequate thirst.  Although one may not “feel” thirsty, or have the desire to drink, maintaining hydration is very important. To encourage drinking, make the water flavorful by adding slices of fresh fruit (orange, lemon, lime, or strawberries) or use water flavor packets. Older individuals may need to be reminded to drink, and need encouragement to do so. Some lose their appetite in the heat and may find it easier to drink their meals. Products such as Boost or Ensure may be helpful when regular meals are not appealing.

Some suggestions to avoid heat-related problems include:

1)      Drink fluids to maintain body water

2)      Avoid over activity to prevent metabolic heat generation

3)      Wear light loose clothing, ingest cool drinks, and use fans or air conditioning

4)      Avoid direct sun and hot, close environments; utilize shade

Remember, as we get older our ability to sense and respond to changes in body temperature are compromised. Loss of appetite and diminished thirst may further compromise an elderly persons ability to thermoregulate. Physiological stress occurs when the body attempts to cool itself, and this stress places the individual at risk for a cardiovascular event. It is necessary for the older adult, and his or her caregivers, to be conscious of methods to avoid heat-related problems.

Mari Hopper is a member of the advisory board for the Center for Healthy Aging and Wellness at the University of Southern Indiana (USI). 

Salas O'Brien