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Your brain works 13 percent slower during a heat wave
A new study from Harvard University researchers found the human brain works 13 percent slower during extreme heat. - photo by Herb Scribner
Does the summer heat have you feeling less intelligent?

Thats not a surprise. A new study from Harvard University researchers found the human brain works 13 percent slower during extreme heat.

The report, which was published in the medical journal PLOS Medicine, studied 44 college students who lived in Boston during a 2016 heat wave, one of the citys hottest in recorded history, according to CBS.

The study split the 44 students into two groups 22 who lived in brick buildings without air conditioners and 22 who lived in air-conditioned dorms. The students were followed for 12 days.

Students were asked to take two cognition tests on their smartphones right after they woke up each day.

The first test asked them to identify the color of displayed words so researchers could measure cognitive speed and the ability to focus on relevant details when irrelevant details are presented.

The second test asked basic arithmetic questions to figure out memory and cognitive speed.

As you might expect, those who lived in the brick buildings without air conditioning performed more than 13 percent worse on math and memory tests than their fellow classmates who lived in air-conditioned dorms.

Most of the research on the health effects of heat has been done in vulnerable populations, such as the elderly, creating the perception that the general population is not at risk from heat waves, lead author Jose Guillermo Cedeo-Laurent said in a press release. Knowing what the risks are across different populations is critical considering that in many cities the number of heat waves is projected to increase due to climate change.

The study said the most significant difference in cognitive function occurred when the outdoor temperatures cooled but the indoor temperatures remained the same.

The scientists said the buildings may be partly to blame, too.

"In regions of the world with predominantly cold climates, buildings were designed to retain heat. These buildings have a hard time shedding heat during hotter summer days created by the changing climate, giving rise to indoor heat waves, study co-author Joseph Allen said, according to the press release.

Memo Cedeno, from Harvard Chan School of Public Health, told The Week this shows that extreme heat can hurt healthy people as much as it affects elderly and weak people.

We see news pieces on heat waves and mortality in older people, but the rest of us feel immune, he noted.

Cedeno said the change in brain function could be related to thirst or loss of bodily fluids and could be because the brain has to work harder to complete simple yet critical functions.

Max Headley, a physiologist at the University of Bristol, told The Week the study makes a mountain out of a molehill since researchers were already aware of the side effects of heat.

To my mind, the observations can be readily explained by simple physiological factors that are entirely predictable. I cant see that its anything to get excited about, Headley said.