As scorching temperatures envelop the UK this week, many are experiencing more than just the physical discomfort of the heat. The intense warmth can significantly impair our mental performance, leaving individuals feeling sluggish and unfocused.
To understand this phenomenon, we spoke with cognitive rehabilitation therapist Natalie Mackenzie, known as The Cognitive Strategist, who shed light on the reasons behind this heat-induced "brain fog" and offered practical strategies to mitigate its effects.
Brain fog, while not a formal medical diagnosis, is commonly described as "muddy thinking, an inability to make decisions, poor attention or just not really feeling ‘on it’ – and it can show up differently to different people," Mackenzie explains. She notes that this state is frequently associated with menopause, perimenopause, tiredness, and, crucially, high temperatures.
During a heatwave, the brain’s hypothalamus, which acts as the body’s thermostat, redirects energy and blood flow towards the skin to facilitate cooling. "Our hypothalamus... constantly monitors body temperature and makes sure that when our temperature goes up, that our body cools down through sweating," Mackenzie clarifies.
This physiological response, coupled with an increased heart rate, diverts substantial energy and blood flow away from the brain. Consequently, cognitive functions such as attention and concentration, which form the base of the cognitive pyramid, are often the first to be affected.
This initial impact can trigger a cascade of issues, affecting other cognitive abilities, including memory. "This creates problems with filtering, distraction, and focus, which then impacts working memory, which is in the next layer of the pyramid," Mackenzie states.
She elaborates that if individuals struggle to focus and attend, they cannot retain or manipulate information effectively for working memory, hindering its transfer to longer-term memory. Higher-level cognitive functions, such as decision-making and executive function, also suffer. "People can’t weigh up information as much, processing speed slows and people often experience a cascading effect that goes down the different cognitive domains," she adds.
Beyond cognitive impairment, heat can also significantly impact mood. Mackenzie observes that impaired decision-making or the body’s stress response can heighten emotional reactions. "In the heat our blood flow and body is focused on our survival instincts of cooling down, which can make us go into a more emotional state," she explains. This can manifest as increased irritability, making people "more snappy, and potentially more reactive and impulsive, in the heat because they are not utilising those executive functions as well as they usually do."
Sleep quality also plays a critical role.
High temperatures disrupt the body’s ability to achieve the necessary dip in core temperature for restorative deep sleep. "Less time in this deep-sleep state impacts our sleep architecture, which then impacts memory consolidation and can impact the glymphatic waste clearance process," Mackenzie warns, referring to the brain’s waste removal system. The following day, this poor sleep compounds the cognitive challenges already posed by the heat.
Furthermore, even minor dehydration can have a profound effect. "Even a small fluctuation in hydration, just tipping into slight dehydration, significantly impacts cognitive function, such as decision-making and focus," Mackenzie highlights.
To combat these heat-related mental challenges, Mackenzie offers several key recommendations:
Stay hydrated: It is crucial to increase fluid intake beyond normal levels during a heatwave to replace water lost through increased sweating.
Adjust your schedule: Where possible, consider shifting demanding activities to cooler parts of the day. "For example, start work earlier in the day when it’s a bit cooler," she suggests.
Change your environment: Seek out cooler spaces. "Try to stay away from hot offices if possible and stick to cooler environments," Mackenzie advises.
Align demanding tasks with cooler times: Plan your day to tackle cognitively intensive tasks, such as making important decisions, during the morning or early evening when temperatures are lower.
Have a slightly cooler shower: A slightly cool shower, rather than an icy one, can help lower body temperature. Cooling wrists and the neck can also help reduce the hypothalamic response.
Create a cool sleeping environment: To protect sleep quality, ensure your bedroom is as cool as possible. "Things like fans, no sheets and light cotton can all help protect that sleep, and help you get more deep sleep," Mackenzie concludes.
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