If you’ve ever felt like you can’t think straight or concentrate on a task when it’s hot and humid, you’re not alone. Many individuals experience this brain fog when temperatures rise to uncomfortable levels, and with summer approaching, it becomes even more of a concern.
There is a growing body of research that demonstrates how environmental conditions — and heat in particular — can affect mental performance. A 2006 study showed that an increase in indoor temperature can reduce work productivity in the office. Researchers evaluated how well participants carried out common office tasks and saw that there is a consistent decrease in performance when the temperature rises above 75.2°F.
This decline in mental function isn’t limited to office workers or adults, and it has been observed in high school students as well. A 2018 study illustrated how a hot 90°F day can reduce educational performance on exams up to 14 percent and result in a 10.9 percent lower likelihood of passing a subject.
So, why does heat affect our ability to think and perform tasks accurately? It may be caused by a variety of factors.
Heat Stress and Sweat
Heat stress occurs when the body can’t cool itself enough to maintain a healthy temperature, which can decrease our cognitive function, explains Lav Varshney, a neuroscientist and associate professor of electrical and computer engineering at the University of Illinois Urbana-Champaign. Plenty of exposure to heat can also blood flow and oxygen supply to the brain, potentially leading to a fainting episode.
“At high enough temperatures, the blood-brain barrier begins to break down and so unwanted proteins and ions can build up in the brain, causing inflammation and messing up normal functioning. Proteins can also unfold, which can cause cell death in the brain,” Varshney says. Experts believe that the hypothalamus might also come into play with how heat affects us. It is the region of the brain that regulates internal body temperature, sending signals to the sweat glands to produce sweat and cool the body off.
“Higher temperatures cause one to lose water due to excessive sweating, which is a compensatory mechanism to maintain body temperature. If not matched by adequate hydration, it can lead to a state of dehydration which can affect your brain function. We all need enough fluid to make our body function optimally,” Amit Mahajan, MD, a neuroradiologist at Yale Medicine and assistant professor at the Yale School of Medicine says. Warmer temperatures are even more of a problem for people with neurological conditions because they might be unable to regulate body temperature and tolerate heat as easily as others. Victoria M. Leavitt, an assistant professor of neuropsychology in the Columbia University Irving Medical Center and chief scientific officer of eSupport Health, explains that “for people with multiple sclerosis, a neurologic condition affecting the brain, exposure to heat has a negative consequence for brain efficiency.”
The increasing body of data describing the educational and economic outcomes of high temperatures highlights the importance of solutions that can effectively address heat’s effects.
Stay Cool and Hydrated
While it’s worrisome how heat can significantly affect our performance, experts say it’s only temporary and various cooling methods can mitigate the negative impacts.
For instance, drinking regularly and eating foods with high water content is an easy and cost-effective way to combat the heat during hot days. “Hydration has its own positive impacts on cognitive function, and drinking water helps support sweating which leads to evaporative cooling,” Varshney says. In addition to the aforementioned studies, other journal articles also document how buildings with air conditioning systems adequately improve thermal conditions, increasing the performance and cognitive function of students and office workers.
Drinking water, using fans, and installing air conditioning are all “excellent solutions for optimal functioning of the body and the brain,” Mahajan says. Other simple ways to keep the room cool, like keeping the curtains drawn to avoid direct sunlight, may be effective as well. However, these solutions only temporarily address one facet of a growing problem: climate change. Hotter days become more common and heat waves more intense due to global warming, which can lead to more heat-related illnesses.
Though most of the impacts of heat stress are temporary, cell death from heat stroke may be permanent, Varshney says. This is why it’s crucial that you avoid high temperatures as much as possible — not just to avoid a temporary cognitive decline, but also to minimize adverse, long-term effects of extreme heat.