(HealthDay News) -- As extreme cold blankets many parts of the United States, one expert warns that frigid temperatures can put people at greater risk not only for hypothermia and frostbite, but also for stroke, heart attack and asthma flare-ups.

Even if you're in excellent physical condition, you should take extremely cold conditions seriously, Dr. Kevin Marzo, chief of cardiology at Winthrop-University Hospital in Mineola, N.Y., cautioned in a hospital news release.

When people face freezing temperatures, their arteries constrict. Narrow arteries can reduce blow flow throughout the body and put stress on the heart. For older people, potentially harmful effects of the cold can be even more serious, Marzo noted.

The number of heart attacks increases by an estimated 53 percent in the winter and the cold-weather constriction of the arteries can also increase people's blood pressure and their risk for stroke. Those with high blood pressure should take extra precautions when dressing for freezing temperatures.

Cold weather can also trigger asthma flare-ups. When people with the condition inhale dry, cold air they may experience bronchospasms, or contractions of the air passages in their lungs. As a result, people with asthma should take their medication before they engage in a physical activity outside, Marzo recommended.

People with circulatory problems, such as Raynaud's disease, should also avoid exercising outdoors when it's extremely cold. In Raynaud's, cold temperatures cause spasms in the blood vessels and cut off circulation to fingers and toes.

Exposure to freezing temperatures can also result in hypothermia, or abnormally low body temperature. When people's body temperature is too low their brain function is affected, Marzo explained. As a result, they are not able to think clearly or move well. The following symptoms are warning signs for hypothermia:

  • Shivering
  • Exhaustion
  • Confusion
  • Fumbling hands
  • Memory loss
  • Slurred speech
  • Drowsiness

Anyone with signs of hypothermia should receive emergency medical attention, particularly if their body temperature falls below 95 degrees Fahrenheit.

If medical attention is delayed or not available, bystanders should move the person with hypothermia to shelter or a warm room. Any wet clothing should be removed. The center of the body should be warmed first with heated blankets or skin-to-skin contact under layers of dry blankets, sheets or towels.