When the weather is sizzling hot

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.

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.

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. 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.
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. 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 affect the way the body reacts to heat, such as reducing sweating, causing dehydration, or keeping you from noticing the heat. Ask your doctor about your medications if temperatures are climbing, especially if you have no air conditioning.

August 2005 Update

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