Here’s a piece of heat advice that sounds almost backward:
Sometimes, a fan can make extreme heat more dangerous for older adults.
But there’s an important word in that sentence:
Sometimes.
Researchers tested older adults in controlled laboratory conditions and found that the effect of a fan depended heavily on temperature and humidity.
In hot, humid conditions, fans reduced cardiac strain.
But in very hot, dry conditions, fan use actually increased cardiac strain.
That doesn’t mean you should throw your fan away.
It means the simple rule “fans are always good in a heat wave” is too simplistic.
Why does humidity change the answer?
Your body cools itself primarily by transferring heat from your skin to the surrounding environment and by sweating.
A fan can help that process.
But in extremely hot, dry conditions, moving very hot air across the body can behave differently.
The researchers found that under very hot and dry conditions, fan use worsened the cardiovascular response.
Skin wetting, on the other hand, reduced cardiac strain.
This was a laboratory experiment
That’s important.
The NEJM study involved controlled exposures lasting about three hours.
A real heat wave can last several days.
People also differ enormously in age, health, medications, hydration, air conditioning, mobility and ability to sweat.
So the study doesn’t provide a universal household rule.
It does provide a reason to think more carefully about temperature + humidity + your health, rather than temperature alone.
What should you actually do?
For older adults during extreme heat, the safest strategy is still to get somewhere genuinely cool whenever possible.
Air conditioning is preferable when available.
If you don’t have AC, a fan can be useful—particularly in hot, humid conditions.
But when temperatures become extreme and the air is very dry, don’t assume that turning the fan to maximum is automatically the safest option.
Cooling the skin with water can help under those conditions.
And if you’re experiencing confusion, faintness, severe weakness, chest symptoms or other signs of heat illness, don’t try to solve the problem with a fan.
Get medical help.
The bigger lesson
Heat advice isn’t one-size-fits-all.
The same fan can have different effects depending on the environment.
That’s why blanket rules can sometimes be less useful than understanding why the recommendation exists.
Evidence & Source
Evidence: Moderate. The evidence comes from controlled laboratory research in older adults, including people with coronary artery disease. The conditions were carefully controlled and do not perfectly reproduce prolonged real-world heat waves.