University Park, Pa. -- If you're over 65 and planning a winter vacation in a sunny climate, be aware that a hot environment puts a strain on an older heart, says a Penn State specialist in the study of the human body's response to heat stress.
"If you exercise vigorously in the heat, the strain is even greater. And, if you have heart disease and exercise vigorously in the heat, you may be in a dangerous situation," says Dr. W. Larry Kenney, professor of physiology and kinesiology at Penn State's Noll Physiological Research Center.
Kenney was a keynote speaker at the Southeastern American College of Sports Medicine annual meeting Jan. 25 to 27 in Columbia, S. C., where he discussed "Aging and Cardiovascular Responses to Heat Stress." His presentation was sponsored by the Speaker's Bureau of the Gatorade Sports Science Institute.
The Penn State researcher has studied the effects of chronological age, fitness, and gender on cardiovascular responses to heat stress for more than 15 years. He says, "Our research has shown that when older people have serious problems associated with the heat, it's usually a cardiovascular problem. People die because heat puts a greater strain on their hearts to pump blood."
Heat waves kill more people each year than hurricanes, tornadoes or volcanoes. And, persons over 65 years of age are 10 to 12 times more likely to die during extended periods of hot weather, he says.
In laboratory studies, Kenney and his research group have shown that, when exposed to high temperatures, young subjects pump more blood to the skin to cool the body. The hearts of older subjects -- even healthy, fit, active subjects -- pump less blood to the skin and do so under more strain, that is, the heart works much harder.
Often, in heat waves, the oldest old will get dizzy when they stand up quickly and may even fall and break bones. To explore the causes of this response, Kenney and his research team have conducted studies with both young and old subjects placed on a tilt table. These studies have shown that younger and older people maintain blood pressure and consciousness in different ways under heat stress. Young people's cardiovascular systems slow blood flow to the skin and muscles to make sure there is more flow to the brain to maintain consciousness. Older subjects cut flow to the gut and liver.
"These results indicate that the combination of heat stress and a big meal could lead to problems for older persons because the meal increases blood flow to the gut, making less blood flow accessible for the elderly to shift to the brain," Kenney says.
Kenney and his research group have explored endurance training, estrogen replacement therapy, heat acclimation and hydration as counter measures to heat's effect on older people. They have found that regular exercise is effective and can increase skin blood flow and cardiac output.
Hormone replacement therapy, too, can be beneficial for women; although, the benefit disappears if the women take combination therapy, estrogen and progesterone, rather than estrogen alone. Heat acclimation and hydration also can help to mitigate heat's effects on the older heart.
However, the Penn State researcher says, "You can make the temperature regulatory system better, but you can't make it young again." He suggests the following hot weather exercise strategy for older men and women: 1) Acclimate. Most heat illnesses occur during the first couple of exercise sessions in the heat. 2) Hydrate. Pay attention to your fluid intake when exercising in hot weather. 3) Use common sense. If you think it may be too hot to exercise at a certain time of day, it probably is. 4) Maintain your fitness level. 5) Educate yourself. Learn the signs and symptoms of heat related illness and emergency treatments. 6) Watch prescription drug effects. Prescription medication can affect thermoregulation in hot environments. Many illnesses and diseases (diabetes, hypertension, etc.) can lower your ability to exercise in the heat. Ask your physician about these effects.