Cognitive function explained
Cognitive function refers to the mental processing your brain does when you concentrate, remember, learn, and reason. A person with cognitive dysfunction might have trouble focusing their attention, remembering facts, or understanding information someone is trying to tell them. As a result, cognitive dysfunction can affect a person’s ability to make informed decisions and to act quickly on those decisions. What many people call “brain fog”—when your mind feels sluggish and you can’t think clearly—is an example of cognitive dysfunction.
Cognitive functions like learning and reasoning rely on our working memory to process information. Working memory is where we take in new information and integrate it with what we already know. But we all have a limited working memory: it can only store a few items at a time, and if it’s overwhelmed, it can’t process the information we try to take in. You can think of your working memory as a container: if it overflows with information, it can’t process properly. So your working memory could be overwhelmed if the size of that container is small or if there is too much for the container to hold at one time.
Disability and cognitive function
People with ADHD, dementia, or traumatic brain injury may have a lower working memory capacity than non-disabled people (in other words, a smaller container). Disabled people also often have more thoughts and worries taking up space in the container, leaving less room to hold information they might need to learn. For example, a person with incontinence might have to make a mental map of all of the public washrooms they might have to use if they go out. A person with episodic disabilities like someone with MS might have to worry about ableist comments or microaggressions from people who see them parking in a disabled parking spot. Intrusive thoughts, traumatic memories, and worries about access to food, housing, and health care can all take up space in working memory and affect mental processing.
Heat and cognitive function
Heat can have a negative effect on cognitive function in many overlapping ways:
Heat can cause dehydration. Brain cells are mostly water, so they need water to function, and just 2% dehydration can decrease “performance in tasks that require attention, psychomotor, and immediate memory skills.”
Heat stress, also called heat exhaustion, is, well, stressful. The stress causes your body to release fight, flight, or freeze stress hormones like adrenaline and cortisol. These stress hormones affect cognitive function because your brain becomes focused on getting you out of immediate danger and doesn’t allow you to take the time to think more deliberatively.
Hot nights can lead to insomnia or having trouble sleeping, and the lack of sleep can also impair cognitive function. Your brain needs sleep to sort out information you’ve learned, and your mind needs rest to be able to devote energy to concentrating and effortful thinking.
The heat itself causes a decrease in cognitive function, especially for relatively complex mental tasks like arithmetic, attention, complex motor coordination, executive function, recall capacity, sustained attention, tracking, and vigilance. Sometimes it really is just too hot to think. Air conditioning can help eliminate these negative effects of heat on cognitive function.
Finally, if heat stress progresses to heat stroke, the most severe and live-threatening type of heat illness, where the body cannot cool down, the cells themselves, including cells in the brain, start to die. This cell death can lead to a long-term decrease in cognitive function.
Staying hydrated and finding ways to keep your body cool, like air conditioning, ice packs, and cool showers or baths, can help reduce the negative cognitive effects of heat. Your brain also needs energy in the form of glucose to work, so although some people lose their appetite in hot weather, reminding yourself to eating or drinking foods that give you sustained energy can help.