What hot weather does to your brain – and how to think through it

With temperatures set to reach 34°C in some parts of the country this week, office workers across the land are deciding to take advantage of their new working-from-home lifestyle by setting

up in their back garden, or local park. All you need is a laptop, sturdy Wi-Fi connection, and maybe a “hood” (a tent for your computer, which allows you to see your screen in direct

sunlight) – and, voila, you have your own outdoor office.

But might your work suffer from large periods of time spent in direct sunlight during a heatwave? That was the intriguing conclusion of a new study published this week in the Scientific

Reports journal. Researchers in Denmark and Greece examined the brain function of eight healthy, active men aged between 27 and 41, who were asked to complete a series of maths and logic

tasks. During some of the tasks, they were exposed to heat lamps positioned to shine onto their lower bodies and back. During others, the heat radiated onto the top and side of their heads.

The men scored lowest when the heat lamps were shining on their heads, researchers found, suggesting that “direct exposure to sunlight – especially to the head – impairs motor and cognitive

performance,” according to lead researcher Prof Lars Nybo, of the University of Copenhagen.

While the study was fairly small, the idea that prolonged exposure to the sun might diminish brain function is one that has been gaining traction among scientists for some time.

Working in high temperatures has long been known to cause hyperthermia, a rise in internal body temperature, which can trigger physical exhaustion. And at the extreme end, those who

experience heat stroke are known to suffer from severe confusion. But now some researchers are coming around to the idea that hot weather might also affect your intellectual faculties in a

far more subtle way – one that you might not even notice happening – by slowing your brain’s processing speed and making it harder to make good decisions.

One review, published in 2003 in the International Journal of Hyperthermia, found that a fairly hot day during the average British summer can easily impair brain capacity. The most severely

affected activities were “vigilance tasks” such as driving, or scanning through a long document, or video clip. The ability to multi-task is also badly affected by the heat, they found. On

the other hand, “mental transformation tasks”, such as working with shapes as designers or engineers might do, are less vulnerable to heat stress, as are “reaction time tasks” that require

you to respond quickly to events – these are important in driving.

Dr Federico Formenti, a physiologist at King’s College London, says that those working outside this week should remember that the impact of heat on brain function is much starker in those

who are moving around.

Even exercise as minor as walking around your garden while you take on a phone call could make a difference. “It is likely that your core body temperature could increase marginally, and that

could have a noticeable effect on your intellectual capacity for a period of time,” he explains. But he thinks that the concentration of sunlight needed to have this effect is only reached

in Britain on the very hottest handful of days each year.

And what is the perilous temperature at which these adverse psychological effects begin to kick in? The 2003 study named 30°C as the danger point - which many parts of the country are

expected to exceed this week. The Copenhagen study, on the other hand, pinpointed 38.5°C - unlikely in the UK, although it is worth remembering that some back gardens can create sun traps

that boost temperatures by a few degrees.

So grab your laptop hood, slap on the factor 50 and enjoy your garden office while it lasts - just don't expect it to land you a promotion any time soon.

So is it time to abandon your outdoor desk and move your glorious garden office indoors? Not quite. Even during a heatwave, scientists say, you can minimise the impact of heat on your

cognitive abilities by following a few small steps.