Is your bedroom really hot? If it is, it may be affecting your memory and other thinking skills.
Heat waves sometimes kill people who are very old, very young or in poor health.
Tais Minga embraces her mother Guadalupe Minga as they wake up inside a building normally used to store small fishing boats, where families took shelter after losing their homes in the earthquake in Pedernales, Ecuador, April 22, 2016.
But new research shows that sleeping in a hot room can affect the thinking ability of even healthy young adults.
This finding comes from Harvard University's T.H. Chan School of Public Health. Researchers there looked at 24 students before, during and after a Boston-area heat wave. Of the 24 students, four slept in rooms with air-conditioning, also called "AC" for short. And 20 slept in rooms without AC.
The experiment lasted 12 days. The temperature of the room without air conditioning, or AC, averaged 26 degrees Celsius (78.8 F). The temperature in the rooms with AC averaged 21 degrees Celsius (70.5 F).
Jose Guillermo Cedeno-Laurent led the study. He is a professor and researcher at Harvard's School of Public Health. He says he and his team considered several conditions in the rooms.
"We measured very intensively, every five minutes, several environmental factors, which include temperature, relative humidity, carbon dioxide and noise, in each of the bedrooms of the participants throughout the duration of the study."
He said they also used devices that recorded physical activity, including heart rate, perspiration, or sweat, and some sleep conditions. The researchers also noted how much water and caffeine the students drank and how much time they spent outside.
Surprising findings
The results were unexpected.
"To our surprise, we found very significant effect of detrimental cognitive function among those students that we included in our study that didn't have air conditioning during this heat wave period."
Basically, they found great harm to the thinking ability of the study participants in rooms without air conditioning.
During the heatwave, students in buildings without AC performed on average 13 percent worse at these tests than those in cooler rooms. Specifically, the students who slept without AC during a heat wave were slower to respond and had difficulty making quick decisions.
Daisy Chang (who was not part of this study) is psychologist at Michigan State University in East Lansing, Michigan. She says there could be other reasons for their poor performance.
"A whole host of reasons could potentially explain this kind of exposure effect. It's not necessarily directly exposure to heat. It [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 rooms without AC had fans and open windows. So, they were louder at night. This could have made sleeping difficult.
On the other hand, air-conditioned rooms can hold higher levels of carbon dioxide. This can also affect a person's ability to think.
However, the students slept better in a cooler room.
"We find that heatwaves are impacting us all. These impacts extend to populations like ]young and healthy university students. And we find significant effect in the way they think -- in their cognitive functions."
Health experts at the Centers for Disease Control and Prevention say that the body temperature of humans should stay close to 37 degrees Celsius (98.6 degrees F). At higher inner temperatures, body operations can start to fail. If the body's temperature rises enough, it shuts down completely and the person dies.
Earlier research centered on how hot weather affects at-risk populations. The CDC says older adults, the very young, and sick people are most at risk.