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

Luke Mintz 23 June 2020 6:00pm BST 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. Telegraph 365 newsletter REFERRAL (article) WHAT CAN YOU

DO? 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. * WEAR A HAT. Covering your head will protect your brain from the most intense of the sun’s rays, authors of the Copenhagen study say.

Prof Andreas Flouis, of the FAME Laboratory in Greece, added: “It is of great importance that people working or undertaking daily activities outside should protect their head against

sunlight.” * EAT LUNCH INDOORS. Dr Formenti says that, in Britain’s climate, heat is only likely to impair brain function during the very hottest hours, around midday. “Work [outside] before

10 or 11am then again after 3 or 4pm, then the effects will be much smaller,” he advises. * INVEST IN A LARGE WATER BOTTLE. It sounds obvious, but dehydration is still the main route

through which heat can make you ill, and it has a particularly marked impact on your cognitive abilities, because brain cells need water to function. A meta-analysis of 33 studies, in 2018,

found that dehydration makes it harder to pay attention to a task, weakening both “executive function” and “motor coordination”. So make sure you take a large bottle of water with you - and

keep glugging.