Ever feel that the arrival of summer sun makes you feel a bit dopey? You wouldn’t be the only one. Soaring temperatures are known for their ability to slow our thought processes, making even everyday tasks seem like a baffling ordeal.
But what is actually happening inside our heads when the heat is on? The explanation appears to lie in the extra work our brain and body have to do to keep us cool.
The brain and body are in constant conversation. When outdoor temperatures change, thermoreceptors which sit near the surface of the skin send signals to the hypothalamus – the brain’s temperature regulation centre.
When things become too hot or cold, the hypothalamus co-ordinates a series of responses to bring body temperature back towards normal (around 37°C). Keeping the core temperature at this level is critical for metabolism, activity of enzymes and many other essential body functions.
Being commander-in-chief of temperature regulation means that the brain becomes rather occupied when having to consistently regulate your temperature.
In hot weather, this means cooling the body down by switching on mechanisms that allow heat to radiate from the surface. This includes diverting blood to the skin, flattening skin hairs and sweating.
These responses are governed by nervous pathways that link the brain to blood vessels and sweat glands. This allows it to fine-tune the amount of heat the body sheds.
But the additional demand that keeping cool places on the brain may therefore leave less capacity for it to perform cognitive tasks which require sustained thought and attention.
This becomes particularly noticeable if you’re also exercising or exerting yourself at the same time. This is because working muscles and metabolism generate heat, which places additional strain on the body and brain’s cooling mechanisms.
Our neurons (nerve cells) may also start to function differently with rising heat. Neurons rely on the flow of electrical currents and the release of chemical neurotransmitters to function. These processes depend upon enzymes, proteins and the movement of charged ions in and out of the neuron – all of which are sensitive to temperature.
Although the brain is normally able to compensate and keep up with these demands, past a certain point the finely controlled balance becomes disrupted. This alters the way neurons fire and communicate with each other, which can affect processes such as memory, decision-making and concentration.
Another potential complication to consider is dehydration, which commonly occurs in hot weather as we lose more fluid in sweat. Failing to replace fluid losses adequately means additional strain is placed on the cardiovascular system as it tries to supply the skin and organs – including the brain – with blood.
Like many other organs, the brain is over 70% water. Even modest dehydration can result in impairment to attention, reaction times and short-term memory.
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This is because dehydration can affect the brain in several ways. It can reduce cerebral blood flow, alter the way that neurons function and even affect the delicate balance of electrolytes needed for normal activity – all of which impact how well our brain works.
Another important consideration is not just how brain and body respond to heat in the moment, but also in the aftermath when they rest and recuperate – namely, through sleep. In hotter weather, it can become increasingly difficult to sleep. And, if you do manage to doze off, the time spent in deeper, restorative sleep may also be short-lived.
In disrupting sleep, hot weather adds another contribution to brain fog: inadequate sleep impairs attention, memory and thinking – furthering the effects of heat on cognitive performance.
Keeping cool
The degree to which the heat affects our thinking will probably vary between people. Some may cope well, whereas others may find difficulty in doing complex cognitive tasks or simple, everyday activities. This will be due in part to individual differences in physiology and heat tolerance.
Perception matters, too. Even a relatively small dip in attention or processing speed can feel much more dramatic when we notice ourselves struggling with something that would usually come easily.
Try not to be hard on yourself if this happens. Take a moment to chill, rehydrate and reclaim your thoughts.
You can fend off some of this summer brain fog by keeping yourself cool as best as you can. Simple measures such as cool clothing, bedding and taking regular breaks from heat exposure do work wonders. Good fluid intake is also paramount to making sure both body and brain stay hydrated.
While it’s frustrating when our brains just don’t feel like they’re firing on all cylinders on hot days, just remember that it’s only a temporary blip. And one that should start to ease off as we cool down.
Dan Baumgardt does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
