Extreme weather is harming our brain health, scientists say

Extreme weather can harm brain health and make several neurological conditions worse, researchers have found.

There is a concerning correlation between environmental changes and neurological health, researchers from University College London wrote in The Lancet Neurology after reviewing hundreds of studies spanning over half a century.

They analysed the impact of extreme weather on 19 nervous system conditions, including stroke, Alzheimer’s, meningitis, epilepsy and multiple sclerosis. They also looked at serious but common psychiatric disorders such as anxiety, depression and schizophrenia.

The researchers found “clear evidence for an impact of the climate on some brain conditions, especially stroke and infections of the nervous system”.

“The climatic variation that was shown to have an effect on brain diseases included extremes of temperature, both low and high, and greater temperature variation throughout the course of day, especially when these measures were seasonally unusual,” Professor Sanjay Sisodiya, director of genomics at University College London’s epilepsy society, said.

Dr Sisodiya said nighttime temperatures may be “particularly important” as hotter nights can disrupt sleep. As heatwaves become more frequent and longer, billions of people around the world are sleeping through higher than normal temperatures.

The researchers noted an increase in hospital admissions, disability or mortality from stroke in higher ambient temperatures or heatwaves.

Studying and understanding how extreme heat affects our health has become urgent as rising temperatures shatter records around the world.

In the past few weeks, Asia has been gripped by heatwaves that scientists have now attributed to the climate crisis.

This April was the hottest on record. A study found that 2023 was the hottest year ever and last summer was the hottest in 2,000 years.

Studies have shown that the body’s temperature needs to drop slightly for a person to fall asleep.

“Poor sleep is known to aggravate a number of brain conditions,” Dr Sisodiya said.

The impact extends beyond the realm of sleep.

The researchers found that people with dementia are at risk of more harm from extreme temperatures, both hot and cold, as cognitive impairment can limit their ability to adapt behaviour to environmental changes.

"Reduced awareness of risk is combined with a diminished capacity to seek help or to mitigate potential harm, such as by drinking more in hot weather or by adjusting clothing,” Dr Sisodiya said.

“This susceptibility is compounded by frailty, multimorbidity, and psychotropic medications.”

The researchers warned that greater temperature variation and heatwaves can lead to increased hospital admissions and deaths related to dementia.

They also said that the additional burden of climate anxiety can make things especially harder for people with existing anxiety and similar conditions. This can make it tricky to deal with the effects of the climate crisis and the changes we need to make to stay healthy.

As more people are exposed to extreme climate, the researchers said, many of the existing studies may be insufficient to fully understand the impact on brain health. They called for more studies taking current and future climate into account.

“This work is taking place against a worrying worsening of climatic conditions and it will need to remain agile and dynamic if it is to generate information that is of use to both individuals and organisations,” Dr Sisodia said.