Too hot to think straight: what a heatwave does to the people behind GMP and GDP
The sneaky thing about heat is that it never feels like what it's doing to you. You feel a bit tired, a bit done with the day. You don't feel the extra mistakes. But they're there.
As I write this, the Netherlands is sweating its way through what might become its first nationwide "super-heatwave." De Bilt has just recorded its hottest 24th of June ever, the KNMI thinks tonight could be the warmest night in its records, and on some roads the asphalt is close to 50°C. Code orange. Terraces full.
Meanwhile, in cleanrooms, warehouses and offices around the country, people are getting worse at their jobs. Their bodies and brains are simply running below their usual level, and most of them don't immediately notice it's happening (or why).
In 2016 a team at Harvard followed young adults through a heatwave and tested them every morning. The ones living or working without air conditioning came out 13.4% slower on a basic attention test and got 13.3% more wrong on simple sums than the people in cooled buildings.
Other research puts the sweet spot for mental work at around 22°C. Climb well above that and your reaction time stretches, your working memory shrinks, and you make more mistakes, especially on the complicated stuff. But why? More people live and work in warm climates than cold ones, so you'd think we'd be used to it by now.
What the heat does to you
During a heatwave your body has just one priority, and it isn't filling in the batch record as precisely as possible. It wants to stay around 37°C. That's it.
To get rid of heat it pushes more blood to the skin and starts sweating, which leaves less for everything else, and your brain is no exception. So your brain carries on working, just on a smaller budget.
The body is also rather fussy about its own temperature. The prefrontal cortex, the part that runs your attention, your working memory, your judgement and your ability to hold your impulses in check, is one of the first to lose its edge once your core temperature climbs.
That's why routine jobs are still reasonably doable on a hot day, while the work that needs real concentration drops in quality. In other words: the harder the thinking, the harder the heat hits.
Dehydration piles on top. You only have to lose 1 to 2% of your body water and your concentration and short-term memory already start to falter, and everything takes more effort than it should.
This gets harder still on the back of a bad night's sleep, which plenty of people are no doubt getting right now. To fall asleep your core temperature has to drop by about half a degree, and you do that by giving off heat to a cooler environment.
If your bedroom stays around 24°C, that doesn't really work, because your body can't get rid of its heat, so you sleep less deeply and wake up more often.
And deep sleep is exactly when your brain does its "cleaning". Get too little deep sleep and that "cleaning" of the brain happens less thoroughly, so you wake up foggier to begin with. You can ride out one night like that, but after a few in a row the deficit adds up.
Add it all up and you get someone who is slower, clumsier, quicker to get irritated and quicker to take a shortcut, working with a head and a body that are both running at less than full strength.
The most annoying part is that the person (often) doesn't notice it themselves. We're bad at judging our own performance when we're hot.
Where this shows up in our work
We monitor temperature with great precision when it comes to the product. We trend the mean kinetic temperature, validate the chillers, set an alarm if it deviates by two degrees. But are we just as precise when it comes to the operators and warehouse staff? Or the lab that's been a touch too warm for weeks because the AC there is playing up? Something to keep in mind this week, with the windows open and everyone just a little not themselves.