When the weather is sizzling hot

Finding some air conditioning, particularly if you're older, could save your life.

France is one of the world's hot spots for tourists. Not long ago, that phrase took on a quite literal meaning for visitors and residents alike. In the summer of 2003, a nine-day heat wave hit the country, causing 14,800 more deaths than usual. The United States has had killer heat waves of its own, including one in Chicago in 1995 that was blamed for nearly 500 deaths.

High ozone levels, nights that never cooled off, and understaffed or ill-equipped hospitals may have helped make the French heat wave particularly lethal. But lack of air conditioning was also a major factor, especially in Paris, where the death toll was particularly high.

Such killer heat waves may become more common. Global warming not only raises average temperatures but causes more extreme weather. Moreover, the European and American populations are getting older and heavier and therefore more vulnerable to the effects of heat. By some counts, more Americans died in the 1990s from heat than from hurricanes, tornadoes, floods, and lightning combined.

Body heat

Heat is a by-product of all metabolic processes. Muscles when they move also generate it. Normally, our bodies do a fine job of shedding the excess. About two-thirds just radiates from the skin into the cooler air outside our bodies. Most of the rest leaves in sweat evaporating from the skin or in moisture in air exhaled from the lungs.

As the air temperature climbs, the amount of heat radiated from the skin falls, and we have to depend more on the evaporation of sweat. But when it's humid, sweat doesn't evaporate as easily because the air is already full of moisture.

Advancing years may make things worse. The older sweat gland becomes fibrotic, so it doesn't produce as much sweat as it used to. Thirst declines with age, so people get dehydrated, further reducing the amount of sweat. The sweat that is produced tends to contain more salt, so electrolyte imbalance can be a problem. Lack of salt in the body can be just as serious as lack of water because it can lead to sudden drops in blood pressure.

Older people are also more likely than younger folks to be taking medications that cause fluid loss (and therefore dehydration) including some laxatives, furosemide (Lasix) for water retention, and other diuretics for blood pressure control. The vulnerability of older people to heat is reflected in the mortality statistics from the French heat wave. Slightly more than two-thirds of those who died were age 75 or over.

Here are some suggestions for avoiding heat-related illness:

1. Listen to your body. Muscle cramps, fatigue, weakness, impaired concentration, confusion, light-headedness, nausea, labored breathing, chest discomfort, and a rapid or erratic pulse can all be signs of trouble. Heed your body's warning signals. If you feel ill — even just a little — get to a cool place, drink plenty of cool water, and be sure that help is available if you don't improve promptly.

2. Head for the AC. Air conditioning is a true lifesaver in a heat wave. Even spending just a few hours in an air-conditioned room helps. Many cities and towns now set up cooling centers during heat waves. There are special programs designed to cut winter heating costs for low-income people, particularly the elderly. Some have suggested that there should be similar "summer cooling" subsidies, perhaps in the form of reduced utility bills.

3. Dress appropriately. Loose, light-colored garments reflect sunlight, making it easier for the skin to cool off and sweat to evaporate.

4. Stay out of the sun, obviously. But you'd be surprised at how many people each summer end up getting sick because they didn't follow this advice. If you're at the beach, gardening, or sitting in the bleachers at a ball game, it is easy to forget how much sun you're getting.

5. Check up on a neighbor. Social isolation is one of the main risk factors for heat-related illness and death. If you know someone who's older, lives alone, and doesn't have air conditioning, stop by to check in and get help if there's a problem.

6. Review your medications. Some medications have a dulling effect on the hypothalamus, the part of the brain that serves as the body's thermostat. As a result, people taking those drugs don't sweat as much as they should. Painkillers may be a hazard because they can reduce awareness of the heat. The fluid loss from Lasix or blood pressure medications normally isn't a problem, but it can be in hot weather because of the risk of dehydration. Some experts say beta blockers may increase the risk of heatstroke by slowing down the heart. You shouldn't quit taking a drug just because it's hot outside, but you might talk to your doctor about your medications if temperatures are climbing, especially if you're not protected by air conditioning.

Heat-related illness: From bad to worse

Heat cramps. Heat cramps are muscle cramps caused by profuse sweating, usually during exercise, and the consequent loss of electrolytes (salts). You have to be careful in high-heat, low-humidity areas like the American Southwest where you may not notice how much you're sweating because the moisture evaporates so fast. You can deal with a mild case of heat cramps by eating salty foods and drinking sports beverages like Gatorade. But Gatorade is sugary, so it has a lot of calories and may not be worth the sodium and potassium boost. The sports drinks — and salt tablets — aren't necessary unless you're sweating quite a bit.

Heat exhaustion. Typical symptoms include weakness, lethargy, wooziness, headache, and nausea. Muscle cramps may also occur. Because heat exhaustion clouds thinking, people often don't recognize the problem as it develops. Serious cases require intravenous fluids and electrolytes. For a mild case, get the person to a cool place and see to it that he or she has fluids to drink, preferably with some salt.

Heatstroke. Heatstroke is a medical emergency — the killer in the killer heat wave. It may start out feeling like heat exhaustion, but the symptoms progress and are more severe: Lethargy, weakness, and confusion develop into delirium, stupor, seizures, and even coma. Body temperature rises drastically, often exceeding 106° F. In younger people, the pulse tends to race. In older people, it's usually slow and weak, and blood pressure may drop. Despite the excess heat, the victim's skin looks pale and feels dry because normal sweating has stopped.

People suffering from heatstroke need to have their body temperatures brought down quickly to prevent permanent cardiovascular, neurological, and other types of damage. Often a cool bath is the best way to do that. Cool compresses on the neck, in the armpits, or in the groin area also quickly lower body temperature.