How Heat Affects the Brain

A heat wave is once again hitting the Northeast, South, and Midwest. High temperatures can have an alarming effect on our bodies, increasing the risk of heart attacks, heat stroke, and death, especially among older adults and those with chronic illnesses. But heat also takes a toll on our brains, impairing our cognitive abilities and making us irritable, impulsive, and aggressive.

How Heat Damages Our Cognition

Numerous lab studies have produced similar results to Dr. Cedeño’s research, with cognitive test scores declining when scientists increase the temperature in the room. One study found that a mere four-degree increase, which participants described as feeling comfortable, led to an average 10 percent decline in performance on tests of memory, reaction time, and executive functioning.

This can have real consequences. R. Jisung Park, an environmental and labor economist at the University of Pennsylvania, looked at high school standardized test scores and found that they dropped 0.2 percent for every grade above 72 Fahrenheit. That may not sound like much, but it can be helpful for students taking a test in an unconditioned room during a 90-degree heat wave.

In another study, Dr. Park found that the hottest days of the school year were the days when students performed worse on a standardized test, especially when the thermometer was over 80 degrees. He said this may be because more heat exposure affected students’ learning year-round.

The effect was “more pronounced for students from low-income and racial minority families,” Dr. Park said, perhaps because they were less likely to have air conditioning, either at school or at home.