When a winter chill blankets most of the nation, it's hard to imagine that older people could be harmed by having their homes too warm.

But that's the conclusion of a new study in the Journal of Gerontology: Medical Sciences that reveals seniors are most cognitively alert when the indoor temperature is 68 F to 75 F. If the temp varies by even 7 degrees in either direction, it doubles their problems with focus.

The harm that excess heat can do is echoed by research in JAMA Network Open that looked at the impact of increasingly high outdoor temperatures.

Too much sweating can lead to low sodium levels and an electrolyte imbalance that increases the risks for everything from low blood pressure to leg cramps, dizziness, even seizures.

In any season, it’s important to make sure to hydrate well. The suggested 64 ounces of water daily is a guide, but you may need more if you are sweating.

Sports drinks that supply electrolytes can be helpful, especially if you are getting exercise — indoors or out. Don't let yourself get thirsty or have a dry mouth.

It's also smart to eat foods such as dark leafy greens, fruit, broccoli, avocados, beans, almonds, and peanuts, which contain electrolytes that help regulate fluid in the body.

For more information on how to stay in top form during and after you are exposed to heat or sweaty exercise, check out "Dr. Roizen's Tips for Living to 100" and "Dr. Oz Dehydration Tips," both on YouTube.