Dehydration and body odor aren't the only things to hate about oppressive heat. According to new research reported by The Guardian, living through a heatwave without relief hampers your ability to think quickly and clearly.

For their study, published recently in PLOS Medicine, researchers at the Harvard T.H. Chan School of Public Health tested the mental performance of 44 students during a heatwave in Boston in 2016. Roughly half the students were living in newer dorm buildings with central AC, with the other half living in older dorms without it.

Over 12 days, researchers had participants take cognition tests on their phones immediately after waking up. The students living without AC took about 13 percent longer to respond to the questions and their answers were about 13 percent less accurate.

The results indicate that even if high temperatures don't pose an immediate threat to someone's health, they can impair them in other ways. “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,” Jose Guillermo Cedeño-Laurent, research fellow at Harvard Chan School and lead author of the study, said in a statement. “Knowing what the risks are across different populations is critical considering that in many cities, such as Boston, the number of heat waves is projected to increase due to climate change.”

Summers are gradually becoming hotter and longer in Boston—a trend that can be observed throughout most of the rest of the world thanks to the rising temperatures caused by human activity. In regions with historically cold winters, like New England, many buildings, including Harvard's oldest dorms, are built to retain heat, which can extend the negative effects of a heat wave even as the weather outside starts to cool. If temperatures continue to rise, we'll have to make a greater effort to keep people cool indoors, where American adults spend 90 percent of their time.

Our thinking isn't the only thing that suffers in the stifling heat. A study published last year found that hot weather does indeed make you crankier—which may not be as bad as bombing a test, but it's not exactly not fun for the people around you.

[h/t The Guardian]