High temperatures are typically accompanied by still air which allows pollutants to stagnate. Hot weather can impact air quality, making it harder to breathe. Also, if a body gets too hot, blood flow to the skin and sweating can both stop: in this case, body temperature soars and brain cells suffer irreversible damage. A body that is dehydrated can no longer cool itself by sweating. An active person can sweat up to 10 litres of water a day, and if this is not replaced, it can lead to dehydration. Sweat is secreted on to the surface of the skin, where its evaporation has a cooling effect – because it takes heat energy from the body to turn the liquid into vapour.īut sweating isn’t a perfect system. If the air outside the body is hotter than inside, the body’s sweat glands – all 1.6 to 5 million of them – get to work. This increases the amount of blood at the surface of the skin allowing it to lose heat – as long as the air is cooler than the body. When the brain senses that the body is warming, the hypothalamus sends messages to blood vessels near the skin, telling to them to dilate. It senses temperature changes, inside the body and out, and makes adjustments to keep it within one or two degrees of 37C. The hypothalamus is the body’s thermostat. Another study linked rising temperatures to higher suicide rates. A recent study in New York found that, on hot days, there were more emergency hospital visits due to substance abuse, mood and anxiety disorders, schizophrenia and dementia. Many people report feeling irritable on hot days, and evidence suggests that extreme heat negatively affects mental health. Proteins and ions accumulate in the brain, causing inflammation. At extremely high temperatures, the blood-brain barrier begins to break down. Hot weather has been linked to reduced cognitive function, judgment errors and higher risk of occupational injury. Studies have shown that extreme heat can affect mental performance. It can be hard to think clearly when you’re too hot.
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