The human brain is highly sensitive to heat. According to scientists studying the impact of climate change on health, higher temperatures trigger the body’s central thermostat and activate stress responses.
Our bodies prioritize cooling over everything else in extreme heat, meaning less oxygen and blood flow reach the brain and muscles. That’s why we feel sluggish, foggy, and unmotivated during hot days.
Such changes arising from heat are more noticeable in temperate regions, with Pakistan being one of them.
It’s not that Karachi afternoons have stretched into infinity; it’s the heat and humidity that make it difficult to move, to function, to want anything other than a nap.
Researchers are increasingly examining how rising global temperatures are affecting sleep patterns and contributing to broader health complications.
“Rising temperatures induced by climate change and urbanisation pose a planetary threat to human sleep, and therefore health, performance, and wellbeing,” a 2024 review published in the journal Sleep Medicine said.
A separate study published in One Earth in 2022 found that humans lost an average of 44 hours of sleep per year during the first two decades of the 21st century compared with earlier periods, linking the trend directly to rising nighttime temperatures.
Chronic sleep deprivation disrupts the body’s ability to recover, increasing the risk of fatigue, drowsiness, and accidents at work or on the road, researchers say.
Over time, accumulated sleep loss — often referred to as “sleep debt” — can worsen metabolic function and increase the risk of obesity, diabetes, cardiovascular disease, and neurodegenerative conditions such as Alzheimer’s, according to neuroscientist Armelle Rancillac.
This heat-induced fatigue is emerging as a public health concern, particularly in regions experiencing prolonged heat waves with little overnight cooling.
Experts say the effects are not just physical but psychological, as chronic heat exposure has also been linked to increased anxiety and decreased mental well-being.
How do we adapt to it, then, in our everyday lives as citizens of a city where the heat doesn’t dissipate even in October?
Cold showers before sleeping, less chai and coffee, more seasonal fruit drinks such as Falsa and unripened mango puree mixed in cold water, drinking lassi, placing wet clothes over windows, placing a tub full of water in the corner of the room, and the list goes on.
As the weather becomes unbearable, more and more people are falling back on localized practices of staying cool.
However, this is not something that can be tackled solely on an individual basis.
With global warming showing no signs of slowing, scientists urge governments to factor in the hidden toll of heat on human behavior and capacity, from productivity drops to rising healthcare needs, as part of broader climate resilience strategies.
