Did you know that aging reduces the body’s ability to cool off? It’s true: That’s why older people are especially susceptible to heat-related ailments such as heat exhaustion and heat stroke when outside temperatures climb. And because excessive heat can impair judgment and cause confusion, you should take precautions to protect yourself from being overcome by heat before you feel too hot.
The body’s cooling system
The body’s thermostat is in a small area of the brain called the hypothalamus. When the hypothalamus senses that body temperature is too high, either because of the weather or an illness, it increases sweat production and dilates blood vessels in the skin. Sweating cools the body through evaporation. Dilating blood vessels brings warm blood from the body’s core toward the surface, permitting heat to be transferred to the environment.
Normal aging reduces the effectiveness of those mechanisms by raising the temperature threshold for sweating, thirst, and heat-related discomfort—especially during waves of hot, humid weather.
Hyperthermia is the general name given to a variety of heat-induced illnesses.
Heat cramps are painful muscle spasms in the legs, arms, or abdomen following strenuous activity. Such cramps occur when the body loses water and salt (the two major components of sweat) because of profuse sweating. Additional symptoms can include fatigue and thirst.
Heat syncope is sudden dizziness or fainting that can occur after standing for an extended period in the heat, upon suddenly standing after prolonged sitting in the heat, and exercising in the heat. Symptoms include pale and sweaty skin, a slowed heart rate, light-headedness, and visual disturbances. Body temperature is normal to slightly elevated.
Heat exhaustion occurs when the body temperature rises, typically to 101˚F to 104˚F. Pulse and breathing rates may be normal or rapid. Symptoms include:
- Weakness or fatigue
- Nausea or vomiting
- Profuse sweating
- Cold and clammy skin
- Darker urine than normal
- Dizziness, light-headedness, or loss of consciousness
- Blurred vision
Heat exhaustion can lead to heat stroke.
Heat stroke is a medical emergency. It occurs when body temperature rises dangerously high (above 104°F) and can’t cool down. High body temperature can cause irreversible brain damage. If not treated promptly, heat stroke can lead to seizures, coma, and death (see inset below).
Classic heat stroke occurs most commonly during heat waves and in people older than 70 who have underlying medical conditions and an impaired ability to get cool or hydrated. Drugs (both prescription and recreational) frequently play a role.
Another form, exertional heat stroke, mostly affects healthy, active people, particularly young athletes, within hours of exercising or overexerting themselves in hot weather.
Heat stroke is most likely to develop when the humidity is high and temperatures are 90°F or above for three or more consecutive days. Humidity makes it feel hotter than it is. The heat index that you hear meteorologists refer to indicates how hot the combination of temperature and humidity feels to the human body.
Warning: Heat Stroke Can Be Fatal
If you suspect someone has heat stroke, call 911 right away. If not treated promptly, the condition can damage the brain, heart, lungs, liver, and kidneys; in some cases, it can be fatal. Here are the signs to watch for.
Risk factors for heat-related illness
Health factors that can increase the risk for classic hyperthermia include:
- Poor circulation
- Inefficient sweat glands, which become more prevalent with age
- Chronic illnesses such as heart, lung, or kidney disease; diabetes; respiratory disorders; and skin disorders such as psoriasis, eczema, and scleroderma
- A salt-restricted diet
- Use of certain drugs that cause the body to increase heat production, including benzodiazepines; tricyclic antidepressants; anticholinergics, such as antihistamines and antiparkinson agents; and certain heart and blood pressure drugs, notably beta-blockers, calcium channel blockers, and diuretics
- Mental states that affect judgment, such as dementia
- Disabilities or illnesses that restrict mobility, such as being bedridden or unable to take care of oneself
Lifestyle factors that make you more susceptible to classic heat stroke include:
- Drinking alcoholic beverages
- Living in an extremely hot residence
- Living alone or being socially isolated
- Not having convenient access to transportation, which prevents people from seeking respite in air conditioning
- Overdressing, especially among older people, who may not feel the effects of a heat wave because our perception of heat decreases as we age
Tips to stay safe
As soon as the air temperature starts to climb, take the following protective steps against heat-related illness:
- Remain indoors in air-conditioning as much as possible. Being in air conditioning, even if only for a few hours, significantly reduces the risk of hyperthermia. If you don’t have air conditioning, try to keep your home cool by keeping shades or curtains drawn during the hottest part of the day, opening windows at night, and using fans. Run errands, exercise, or do other outdoor activities early to avoid the hottest part of the day. Spend time in air-conditioned environments, such as movie theaters, libraries, shopping malls, and senior centers. Your community may provide cooling centers where you can spend the day.
- Stay hydrated. Sip water all day long, whether you feel thirsty or not: Older adults are less likely than younger people to recognize thirst. Avoid alcoholic beverages. If you’re on a diet that restricts liquids or you have heart, kidney, or liver disease or epilepsy, check with your doctor first before you increase your fluid intake.
- Cut back on physical activity. Avoid strenuous exercise during heat waves. Adjust how much you walk, garden, and so forth. In some instances, it may be possible to exercise early in the morning or in the evening. Be sure to rest at the first sign of feeling fatigued, lightheaded, or hot.
- Take baths and showers. Because water conducts heat away from the body, taking tepid baths and showers is a good cooling technique.
- Wear appropriate apparel. Loose-fitting, light-colored, lightweight garments made of natural fibers that “breathe,” such as cotton, are best. A wide-brimmed hat can provide shade and keep your head cool.
- Talk with your doctor about your medications. It may be possible to alter a drug or dosage that could cause a problem. Under no circumstances should you change your medication on your own.
First aid for hyperthermia
Heat syncope and heat cramps can usually be relieved by drinking plenty of water and resting in a cool place. If a person’s symptoms don’t go away within 30 minutes, he or she should seek medical attention.
To treat heat exhaustion and stop it from turning into heat stroke, take these steps:
- Move the person out of the sun into a shady, cool place, preferably one that’s air-conditioned.
- Have the person lie down with legs elevated.
- Loosen or remove any tight clothing.
- Offer cool (not ice cold, which can cause stomach cramps) water, fruit juice, or a sports drink with electrolytes like Gatorade to replenish sodium lost during sweating. You can also mix one to two quarts of water with two teaspoons of salt. Don’t offer salt tablets, since they can induce vomiting and increase dehydration. Avoid offering alcoholic or sugary beverages.
- Apply an ice pack, a cold compress, or cool, wet towels to the back of the neck, armpits, and groin, to help cool the person.
- Encourage the individual to shower, bathe, or sponge off with cool water.
- Splash or spray the person with cool water (such as with a garden hose), then fan the person’s skin or have him or her sit in front of an electric fan if one is nearby.
- Watch the person carefully for any changes in condition. If symptoms worsen or don’t improve within 30 minutes, or if the person has an underlying heart disorder, call 911.
If the victim is exhibiting signs of heat stroke (see inset above), emergency assistance should be sought immediately. Without medical attention, heat stroke can be deadly. After you call 911, try to keep the person cool using the techniques outlined above. However, only offer water if the person is alert and can swallow. You can immerse a person in a tub of cool water or in a body of water such as a lake or a stream.
This article first appeared in the July 2019 issue of UC Berkeley Health After 50.
Also see Exercising Safely in the Heat.
Published July 01, 2019