You know that hypothermia is a risk when you’re outdoors and not adequately prepared for cold temperatures. But it’s also a potentially deadly hazard for certain folks even indoors—and in a house that you might think is comfortably warm, such as when the indoor temperature is in the 60s.

Why? As we age, the ability to maintain a constant internal body temperature diminishes. So does the ability to recognize temperature changes—to realize how cold you really are.

The biggest risk is for people over 65, especially if they have certain health conditions (underactive thyroid, decreased mobility because of a chronic ailment) and/or take medications (antidepressants, antipsychotics, cardiac drugs) that affect how the body regulates core temperature. Add a few alcoholic drinks, and there’s real trouble—drinking alcohol might make your skin feel warmer, but it actually steals heat from your core.

Put it all together, and hypothermia, a health emergency that occurs when the body’s core temperature falls below 95°F, can happen even indoors in a house where the thermostat is set lower than 68°F. Warning signs, which might creep up gradually—slurred speech, drowsiness, apathy, confusion and irritability—won’t necessarily alert a chilled senior to put on more clothing and turn up the heat.

Bottom line: If you’re at risk, or are watching out for someone who is, make sure the thermostat is set at least to 68°F, especially during multiple days in a row of extreme cold…layer up…move around…and eat regularly, since burning calories helps keep the body warm.