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During the 2003 European heatwave, for example, about 7% of the excess deaths involved
direct neurological problems. Similar figures were also seen during the 2022 UK heatwave.
But heat can also alter other ways our brains function 3 making us more violent, grumpy
and depressed. (Find out more about how heatwaves warp the mind in this article by Zaria
Gorvett.)
So, as the world warms due to climate change, what can we expect the effect on our
brains to be?
The human brain is, on average, rarely more than 1C (1.8F) higher, on average, than our
core body temperature. Yet our brains 3 as one of the more energy-hungry organs in our
bodies 3 produce a fair amount of their own heat when we think, remember and respond
to the world around us. This means our bodies have to work hard to keep it cool. Blood circulating through a network of blood vessels helps to maintain its temperature, whisking
away excess heat.
This is necessary because our brain cells are also extremely heat sensitive. And the function
of some of the molecules that pass messages between them are also thought to be temperature dependent, meaning they stop working efficiently if our brains get too hot or too
cold.
"We don't fully understand how the different elements of this complicated picture are affected," says Sisodiya. "But we can imagine it like a clock, where all the components are no
longer working together properly."
Although extreme heat alters how everyone's brains work 3 it can, for example, adversely
affect decision making and lead to people taking greater risks 3 those with neurological
conditions are often the most severely affected. This is for many reasons. For example, in
some diseases, perspiration may be impaired.
