In a Personal View article, published in The Lancet Neurology, the team emphasise the urgent need to understand the impact of climate change on people with neurological conditions – in order to preserve their health and prevent worsening inequalities.

Following a review of 332 papers published across the world between 1968 and 2023, the team, led by Professor Sanjay Sisodiya (UCL Queen Square Institute of Neurology), said they expect the scale of the potential effects of climate change on neurological diseases to be substantial.

They considered 19 different nervous system conditions, chosen on the basis of the Global Burden of Disease 2016 study, including stroke, migraine, Alzheimer’s, meningitis, epilepsy and multiple sclerosis.

The team also analysed the impact of climate change on several serious but common psychiatric disorders, including anxiety, depression and schizophrenia.

Professor Sisodiya, who is also Director of Genomics at the Epilepsy Society and a founding member of Epilepsy Climate Change, said: “There is 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.
“Nighttime temperatures may be particularly important, as higher temperatures through the night can disrupt sleep. Poor sleep is known to aggravate a number of brain conditions.”

The researchers found that there was an increase in admissions, disability or mortality as a result of a stroke in higher ambient temperatures or heatwaves.

Meanwhile, the team state that people with dementia are susceptible to harm from extremes of temperature (e.g. heat-related illness or hypothermia) and weather events (e.g. flooding or wildfires), as cognitive impairment can limit their ability to adapt behaviour to environmental changes.

They write:

“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.
“This susceptibility is compounded by frailty, multimorbidity, and psychotropic medications. Accordingly, greater temperature variation, hotter days, and heatwaves lead to increased dementia-associated hospital admissions and mortality.”

In addition, incidence, hospital admissions, and mortality risk for many mental health disorders are associated with increased ambient temperature, daily fluctuations in temperature, or extreme hot and cold temperatures.

The researchers note that as adverse weather events increase in severity and global temperatures rise, populations are being exposed to worsening environmental factors that may not have been severe enough to affect brain conditions in some of the earlier studies they reviewed as part of the analysis.

As a result, they say it’s important to ensure that research is up to date and considers not only the present state of climate change but also the future.

Professor Sisodiya said: “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.
“Moreover, there are few studies estimating health consequences on brain diseases under future climate scenarios, making forward planning challenging.”
He added: “The whole concept of climate anxiety is an added, potentially weighty, influence: many brain conditions are associated with higher risk of psychiatric disorders, including anxiety, and such multimorbidities can further complicate impacts of climate change and the adaptations necessary to preserve health. But there are actions we can and should take now.”

The new article is published ahead of The Hot Brain 2: climate change and brain health conference, which is led by Professor Sisodiya and jointly organised by UCL and The Lancet Neurology.

The aims of the meeting are to raise awareness about the risks of climate change for the brain and neurological healthcare, to nurture global collaborative research, and to promote action against climate change and foster adaptation strategies.

The research was funded by the Epilepsy Society and the National Brain Appeal Innovation Fund.

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