Harvard Men's Health Watch

Heat wave

Global warming is on everyone's mind, as it should be. But even before climate changes kicked in, summers were hot. And whatever the future holds for our environment, summers will be hot.

Summer's heat is more than a hardship, it's a killer. In an average year, about 200 Americans die from heat-related illnesses, and in hot summers the toll can double. Many more people suffer less severe heat-related illnesses.

Summer's heat is as predictable as winter's chill. But if heat is inevitable, illness is not. In fact, a few simple precautions can protect you from becoming a seasonal statistic.

Staying cool

Even on a crisp November day, your body has to work at staying cool. That's because your body generates heat as a byproduct of all its metabolic processes. If you retained that heat, your temperature would shoot up dramatically. To prevent that, your body is constantly shedding heat.

The body dissipates most of its excess heat through your skin. But to succeed at that, two conditions must prevail. First, your circulation must be able to pump plenty of blood to your skin. Second, the air must be cooler than your blood, so you'll give up heat by conduction (the direct transfer of heat from a warm body to a cooler environment); add a cooling breeze, and you'll also lose heat by convection (heat exchange enhanced by air flow).

Under normal circumstances, conduction is an efficient mechanism for heat loss; that's why you take off your shirt in summer and put on a sweater in winter. But when the air temperature approaches body temperature, or when exercise sends your body's heat production soaring, conduction won't do the trick. Now evaporation kicks in; you'll sweat profusely, and as sweat evaporates, it will carry away your excess body heat. But as humidity climbs, evaporation slows, then stops.

Heat-related illnesses result from an imbalance between man and nature. Nature contributes high air temperatures, high humidity, the radiant energy of sunlight, and still air. You can't do much to change nature, but you can control the human elements that contribute to heat illnesses; undue exposure to sun and heat, unwise exercise, inappropriate clothing, and dehydration head the list.

Heat-related illnesses

Although mental irritability is the most common response to conditions that are too darned hot, grumpiness does not qualify as a true heat-related illness. In medical terms, heat can produce three distinct patterns of injury:

Heat cramps. Most men experience muscle cramps from time to time. It's okay to dismiss the occasional cramp as a simple "charley horse," but if you get recurrent cramps in hot weather, you could be heading for trouble. Heat cramps signal dehydration severe enough to deprive muscles of the extra oxygen they need to exercise. The remedy: slow down, tank up with cool water, stretch out and gently massage the tight muscle, and get out of the heat.

Heat exhaustion. Heat cramps are painful but not threatening; that's because body temperature is normal even though muscles are in spasm. But in heat exhaustion, body temperature is high, often above 103° F. Other symptoms include weakness, lethargy, loss of concentration, headache, and nausea; muscle cramps may also occur.

Heat exhaustion impairs mental clarity and judgment, so you may not recognize the problem as it develops. Be alert for early symptoms and take corrective action as soon as they appear. Be watchful, too, for signs of heat exhaustion in others; confusion, profuse sweating, and flushed, clammy skin are among the tip-offs. Move the victim to a cool place as soon as possible; remove his clothing and fan him en route. You should apply ice packs if they're available, cool fluids if not. Cool fluids on the skin will lower body temperature, but it's even more important to get them down the hatch. Don't force someone who is weak and confused to drink too much too fast, but keep offering small amounts of fluid until hydration is restored.

Heat stroke. It's the illness that kills each and every summer, even with treatment. There are two distinct forms of heat stroke. Classic heat stroke is the more common; it's the major problem during heat waves, which is why it's also called epidemic heat stroke. The typical victims are elderly people who stay in their stifling apartments without air conditioners or fans. Many have chronic illnesses such as diabetes, and some take medications that reduce their ability to sweat. The other form is exertional heat stroke, also called sporadic heat stroke because it occurs in isolated cases rather than in community-wide outbreaks. The typical victim is a man who exercises vigorously in the first few days of a hot spell; many are young, and most are out of shape. Marine recruits and weekend warriors exemplify men at risk; heavy clothing, exposure to direct sunlight, and dehydration often add fuel to the fire "" and the hazard is greatest when it's least expected. The runners who turned out for the Chicago Marathon in October 2007 had every reason to expect a typical autumn day. Instead, the temperature spiked into the high 80's, producing so many problems that officials halted the race while it was in progress. Even so, there were hundreds of heat injuries severe enough to require emergency medical treatment, and a 35-year-old runner collapsed and died.

Heat stroke is a medical emergency. It starts out looking like heat exhaustion, but its symptoms are more severe, and they progress more quickly, as lethargy, weakness, and confusion evolve into delirium, stupor, coma, and seizures. Body temperature rises drastically, often exceeding 105° or 106°. Even with so much excess body heat, the victim's skin may be pale and inappropriately dry due to a failure of normal sweating.

Heat stroke is a killer because it damages the heart, liver, kidneys, brain, and blood clotting system. Survival depends on prompt transfer to an emergency ward for aggressive treatment. Expert metabolic and cardiovascular care is mandatory, but even in this era of high-tech medicine, the best way to lower a heat stroke patient's temperature is to immerse him in a bath of ice water or to spray him with cold water and turn on a strong fan.

Other summer woes

Sunburn "" and suntan. There is no such thing as a healthy tan. The ultraviolet radiation in sunlight is dangerous; a single excessive dose can cause a painful sunburn, but even mild, gradual exposures will cause cumulative damage, leading to premature wrinkling and to skin cancers, including deadly melanomas. Stay out of the sun, especially between 10 a.m. and 2 p.m. when its rays are strongest. Wear a wide-brimmed hat and light-colored, long-sleeved clothing. Even on hazy or cloudy summer days, put on a broad-spectrum sunscreen with an SPF rating of at least 15.

Sun blindness. The ultraviolet rays in sunlight can damage the eye every bit as much as the skin. The cornea is at particular risk. Even a single intense exposure can cause photokeratitis, sun blindness. The symptoms are pain and light sensitivity, often accompanied by redness, tearing, and uncontrollable blinking. Fortunately, the cornea will usually repair itself in 12 to 48 hours. But repeated low-level ultraviolet exposure can cause cumulative damage to the lens, ultimately resulting in cataracts. Sunglasses will prevent both problems if they have high-quality lenses that screen out UV rays. Avoid lenses that are rated as "cosmetic." Instead, look for sunglasses rated "general purpose" or "special purpose" that screen out 99% to 100% of UVA and UVB, and 75% to 90% of visible light.

Dehydration. Summer heat stimulates sweating; perspiration will help keep you from overheating, but it will also dry you out. Fatigue, impaired concentration, excessive thirst, a salty taste in the mouth, dark-colored urine, and rapid weight loss are among the symptoms. The remedy is simple: fluids. Water is even better than sports drinks, and salt tablets are virtually never indicated. Don't count on alcoholic or caffeinated beverages, which have diuretic properties.

Fungal infection of the skin. The skin is normally protected from infection by its tough, dry outer layer, the epidermis. Perspiration can damage the epidermis, however, opening the door to infection by a group of fungi called dermatophytes. Fortunately, they're not as fearsome as they sound, since they don't cause anything more serious than athlete's foot, jock itch, and ringworm. Again, prevention is easy: stay dry. Change socks and underwear that are damp, and towel off carefully after showering or swimming. Over-the-counter anti-fungal powders and ointments will usually cure these infections, but prescription medications are available for tough cases.

Insects. Most mosquito bites are little more than a nuisance, and bee stings are little more than a pain. But if the mosquito that bites you happens to be carrying West Nile virus or if you happen to be allergic to bee venom, a nuisance can turn into a major illness, a pain into a medical emergency. And ticks can carry Rocky Mountain spotted fever, Lyme disease, or the newest scourge, Ehrlichiosis.

To avoid bites, don't choose bright clothing or sweetly scented aftershave lotion that might attract insects. Wear long pants and long sleeves, particularly at dusk when insects are most active. Use insect repellents containing 10% to 30% DEET or 7% picaridin; products containing oil of lemon eucalyptus (also known as PMD) can help as well. Carry a bee-sting kit if you are allergic to insect stings, and discuss desensitization treatments with your doctor. Finally, inspect your skin for ticks at the end of a day in the country. If you see a tick, don't squash it into your skin. Instead, use tweezers to grasp the tick close to its mouth, then remove it with a slow, steady pull.

Air pollution. City dwellers, in particular, seize on summer as the time to get outdoors. Unfortunately, the quest for fresh air is often rewarded by ill winds.

Air pollution is a major problem in industrial America. Fossil fuel combustion is the culprit; industry accounts for about two-thirds, motor vehicles the rest. Tailpipes and smokestacks spew sulfur dioxide, nitrogen oxide, carbon dioxide, carbon monoxide, and particulates into the air; ozone is added as a result of sunlight-triggered chemical reactions among these chemicals. But what goes up must come down. In the summer, atmospheric inversions trap pollutants in the hazy smog that lingers over urban and industrial areas.

Our air quality is improving. There is little risk of an air pollution disaster such as the "black fog" that killed 4,000 Londoners in 1952. Still, men with emphysema, asthma, and heart disease should listen to air-quality alerts; keep your air conditioner running until the fresh air outside really is fresh.

Prevention

An ounce of prevention will go a long way, but for heat-related illnesses, a quart is even better. That's because hydration is essential, and it takes a lot of liquid to preserve your body's circulation and replace the fluid lost in sweat. Even if you're sedentary, you may need 10 to 12 cups of water a day in hot climates; if you exercise, you'll need much more. Cool liquids are best; despite the popularity of sports drinks, nothing beats water.

Hydration is necessary, but it's not sufficient to stave off summertime heat. Here are a few additional tips:

  • Get away from the heat. An air-conditioned room is best, but even a fan will help. If you can't cool your own home, take refuge with a friend or relative. Some communities provide emergency cooling centers during heat waves.

  • When you go out, stay out of the sun and avoid the midday heat as much as possible. Wear loose-fitting, light-colored garments.

  • Don't exercise when it's hot or humid. If it's humid and above 80° to 85°, jump in a pool or work out in an air-conditioned gym. If you exercise outdoors, do it in the early morning or evening. Slow down; walk instead of jogging or use a cart instead of walking the golf course. Take breaks and quit early.

  • Above all, listen to your body. Muscle cramps, fatigue, weakness, nausea, impaired concentration, confusion, lightheadedness, 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 a little ill "" get to a cool place, drink plenty of cool water, and be sure help is available if you don't improve promptly.

Good old summertime

Even with an occasional hot day, summer is a wonderful season. The days are long, the nights are comfortable, and the hectic pace of modern life slows down a bit. But summertime can cause health problems, ranging from sun exposure and poison ivy to insect bites and air pollution. Among summer's seasonal hazards, heat is the worst "" particularly when it lingers day after day.

To keep the living easy this summer, understand how your system handles heat, listen to warnings from the weather service and your body, and take all necessary precautions. It's the cool thing to do.