How to protect yourself in dangerous, freezing weather

The freezing weather slamming three-quarters of the country is posing serious health risks. The frigid temperatures can lead to hypothermia, compromise lung function, and trigger confusion or other neurological effects.

The elderly and infants are more vulnerable to hypothermia, according to CBS News' Dr. Tara Narula. She warned it's important to be aware of the symptoms "because they say the cold makes you dumb."

"It really can affect your mental thinking, it can make you sluggish, it can affect your judgment, your coordination. So you may not realize that you're that cold," Narula said Tuesday on "CBS This Morning."

You're at risk for hypothermia when your body temperature falls below 96 degrees Fahrenheit (35 degrees Celsius).

"It's really a balance between our heat production through metabolism and what we're losing, heat wise, from our skin and from our breathing. And so we try to make heat, so we shiver to generate heat, our blood vessels peripherally in our arms and legs will constrict to keep the blood closer to our core, our heart, kidney, lungs, the vital organs. Our adrenal glands or thyroids will all sort of push out hormones. But when this system fails, then you are at risk for hypothermia," Narula said.

The weather could also strain your cardiovascular health. As CBS News correspondent DeMarco Morgan reported, at least three people died after shoveling snow over the weekend. In upstate New York, 70-year-old Frank Demasi was found on his front steps Monday after suffering a heart attack Sunday night while trying to clear his property.

"There are a lot of factors that play into this. We know that the blood pressure goes up in the winter, cholesterol levels can go up. The blood can be more prone to clotting," Narula said. "And as I mentioned before, the blood vessels constrict, both peripherally and also they can constrict when — the actually coronary arteries can constrict. So you have a lack of supply and increase in demand."

While you may take precautions if you have underlying heart disease, Narula said the problem is that many people aren't aware they have heart issues. So she suggested warming up, using a small shovel, taking frequent breaks, and pushing the snow instead of lifting large amounts.

"Don't drink alcohol or eat a heavy meal before you go out. And don't go out first thing in the morning because we know that first thing in the morning is when you're more likely to have a heart attack — that's kind of the time you see that circadian rhythm," she said.

Watch out for frostbite as well, as your skin is your body's largest organ. The tissues begin to freeze and you lose feeling in the areas affected, Narula said.

"This can affect the nose, the chin, the ears, the fingers or the toes. And, so you want to keep those covered. They suggest mittens instead of gloves. Those will work better. And if you start to notice that you're having numbness or tingling or burning, you want to seek help for that immediately," Narula said. Rewarm the skin with warm water or use body heat like under the armpits to heat up the tissues. Don't hold freezing limbs over radiators since you won't know if it's too hot to burn yourself, she advised.