Is your dorm room stifling hot? That might impact your memory.
New research shows that heat can affect even healthy young adults intellectually, with worse cognitive performance observed in students who slept in a non-air-conditioned room during a heat wave.
Researchers from Harvard University recruited 24 students who slept with air-conditioning and 20 who slept in rooms without AC before, during and after a Boston-area heat wave.
They recorded temperature, relative humidity, carbon dioxide and noise in each bedroom throughout the study.
The indoor temperature of the non-air-conditioned dorm averaged 26.3 C (79.3 F) compared with 21.4 C (70.5 F) in the dorm with air-conditioning.
Each participant wore an activity monitor to measure heart rate, perspiration and sleep quality. When the students woke up each morning, they were tested for how quickly and accurately they completed two cognitive tests that measured memory and reaction.
Researchers also noted how much water and caffeine the students consumed, and how long they spent outdoors each day.
After 12 days, researchers were surprised by the data.
“We found very significant effect of detrimental cognitive function among those students that didn't have air-conditioning during this heat wave period,” said lead author Jose Guillermo Cedeno Laurent of the Harvard T.H. Chan School of Public Health.
The students who didn’t have air-conditioning performed significantly worse on the basic cognitive tests. In particular, going without AC during a heat wave hurt their reaction time when they had to make quick judgments.
“Their study really demonstrated that exposure to heat can have all these potential effects on people’s daily activities,” said Daisy Chang, an organizational psychologist at Michigan State University in East Lansing.
“A whole host of reasons could potentially explain this exposure effect,” Chang noted. “It’s not necessarily directly exposure to heat. [The heat] could have affected their sleep quality so they're less rested, they have less energy, or mental resources, or ability to focus.”
The dorms without AC were louder at night because of fan and street noise, which could have disrupted sleep.
And while air-conditioned rooms can hold higher levels of carbon dioxide, which can have a negative impact on cognition, the students slept better in a cooler room.
“We find that heatwaves are impacting us all,” Cedeno said. “These … extend to those like the young and healthy university students. And that we find significant effects on the way they think - their cognitive functions.”
Extreme heat exposure is the biggest killer of all climate phenomena in the United States, killing 7,000 people between 1999 and 2010. Previous research focused on how hot weather affects at-risk populations like the elderly and the very young. And 2016 was the hottest year on record for the past 200 years.