Heat intolerance refers to the body’s diminished ability to regulate its core temperature in response to heat stress, a challenge that disproportionately affects older adults. Advanced age significantly compromises the body’s cooling mechanisms, making individuals 65 years and older far more vulnerable to heat-related illnesses compared to younger populations. This increased susceptibility results from fundamental biological changes that impair heat dissipation, compounded by chronic health conditions and the use of certain medications.
Physiological Changes That Increase Vulnerability
The human body’s primary defenses against overheating—sweating and increased blood flow to the skin—become less efficient with age. A notable change involves the thirst mechanism, where the body’s signal to drink fluids is often delayed or reduced in older adults. This blunted sensation means older individuals may not recognize the onset of dehydration, leading to a fluid deficit that hinders the body’s overall cooling capacity.
The body’s reliance on evaporative cooling is impaired by a decline in sweat gland function, sometimes referred to as anhidrosis. Older adults require a higher core body temperature threshold before the onset of sweating begins compared to younger people. Even when sweating does occur, the maximum sweat rate is often attenuated, delaying the overall cooling effect.
Circulatory changes further diminish the body’s ability to shed excess heat. When a person is hot, the cardiovascular system shunts blood to the skin’s surface (cutaneous vasodilation) to allow heat to escape into the environment. Older adults show an attenuated response, increasing skin blood flow two to three times less effectively than younger individuals. This reduced peripheral circulation forces the body to store more heat. Furthermore, age-related decreases in total blood volume and functional changes mean the heart has a reduced capacity to increase cardiac output sufficiently to support both the organs and the cooling needs of the skin.
How Health Conditions and Medications Contribute
Beyond the natural decline in thermoregulatory function, chronic medical conditions and common prescriptions significantly amplify heat risk. Conditions affecting the cardiovascular system, such as heart disease, impair the body’s ability to sustain the increased cardiac output required for effective skin cooling. Similarly, conditions like diabetes can disrupt fluid and electrolyte balance, making the body less resilient to the dehydrating effects of heat.
Many common medications interfere with the body’s innate cooling mechanisms, either by promoting fluid loss or by blocking the signals that initiate sweating or vasodilation. Diuretics, often prescribed for high blood pressure or heart failure, increase urine output, which can quickly lead to dehydration and electrolyte imbalance during hot weather. Certain psychiatric medications, including some antidepressants and antipsychotics, can interfere with the central nervous system’s control over temperature regulation, specifically affecting the hypothalamus.
Medications used to manage blood pressure, such as beta-blockers, can reduce the amount of blood flow directed to the skin, restricting the body’s ability to release heat. Anticholinergic drugs, found in medications for conditions like overactive bladder and some allergy treatments, can directly inhibit sweat gland function, preventing evaporative cooling. Individuals taking multiple medications face a synergistic increase in risk, as several temperature control mechanisms may be compromised simultaneously.
Identifying Heat Exhaustion and Heat Stroke
Recognizing the signs of heat-related illness is complicated in older adults because symptoms can be subtle or atypical. The two primary concerns are heat exhaustion and the more severe heat stroke. Heat exhaustion is a milder form of illness resulting from a loss of water and salt, typically presenting with heavy sweating, cold, pale, or clammy skin, muscle cramps, and a fast but weak pulse. A person experiencing heat exhaustion will usually have a body temperature below 104°F (40°C) and will generally remain mentally alert.
Heat stroke, in contrast, is a life-threatening medical emergency characterized by a failure of the body’s temperature control system. The most telling sign is a high core body temperature, typically 104°F (40°C) or higher, coupled with central nervous system dysfunction. In older adults, this brain dysfunction may manifest quickly as confusion, slurred speech, disorientation, or delirium. While a younger person with heat stroke might have hot, dry skin, older adults may not sweat at all, though the skin may still be hot to the touch.
Essential Prevention and Response Strategies
Proactive measures focusing on environmental control and consistent hydration are necessary to mitigate the risk of heat illness in older adults. Staying in an air-conditioned environment is a primary defense, and if home air conditioning is unavailable, utilizing public cooling centers or air-conditioned spaces like libraries and malls is advisable. Simple household adjustments, such as closing curtains and blinds during the day and avoiding the use of the stove or oven, can significantly reduce indoor temperatures.
Hydration practices should involve drinking fluids continuously throughout the day, rather than waiting for the sensation of thirst, which is often unreliable with age. Water and clear juices are recommended, while beverages containing alcohol or caffeine should be limited as they can promote fluid loss. Wearing loose-fitting, lightweight, and light-colored clothing helps heat escape the body more easily. Furthermore, outdoor activity should be restricted to the coolest parts of the day, such as the early morning or late evening.
If a person shows signs of heat exhaustion, they should be moved immediately to a cool area and given sips of water, provided they are awake and can swallow. For suspected heat stroke, emergency medical services must be called immediately. While waiting for help, the individual should be moved to the coolest possible location, and efforts must be made to lower their core temperature rapidly. This can be achieved by placing cool, wet cloths or ice packs on areas where large blood vessels are close to the skin’s surface, such as the neck, armpits, and groin.