CLIMATEWIRE | A broad range of brain conditions, from migraines to strokes, are made worse by extreme heat, new research shows.
The most direct impact of high temperatures is that they can mess with the brain’s wiring. But extreme heat creates a variety of other problems, too, for those diagnosed with epilepsy, schizophrenia, Alzheimer’s, Parkinson’s and other diseases, according to a May study from 24 researchers published in The Lancet Neurology journal.
The human brain does best when outside temperatures are between 68 to 79 degrees Fahrenheit, said Sanjay Sisodiya, the lead author of the study and a neurologist at University College London. It’s where “we feel thermally comfortable without having to do additional things.”
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But if the “temperature's taken out of that range,” he added, then the way the body’s components interact “can be disrupted.”
A scientist not affiliated with The Lancet Neurology study made a similar observation.
While the brain’s temperature “is really well regulated,” excessive outside temperatures distort some of the brain’s support network — especially for those of advanced age, said George Perry, a biology professor at the University of Texas at San Antonio.
“At high temperatures you have less oxygen being transported and [altering] metabolic processes to end up stressing a lot of different systems that keep the brain functioning normally," he said.
Perry was one of the first scientists to speculate about the link between climate change and neurological disorders back in the early 2010s.
The new study says impaired communication between brain cells can result from heat-induced “dehydration, electrolyte losses, and psychological intolerance of heat.”
As part of their research, Sisodiya and his co-authors surveyed 332 academic papers. They found extreme heat had “broad and complex adverse effects” on a variety of brain conditions — sometimes for very different reasons.
For example, Sisodiya said that heat waves themselves can contribute to strokes, but extreme heat also is associated with increased pollution that compounds the probability of having a stroke. High temperatures also can interrupt sleep and disrupt supply chains for medication.
The study found that climate change can influence factors such as “admissions to hospital for psychiatric disorders, or vector range extension and sociopolitical upheaval” that might indirectly aggravate mental disease systems.
One indirect example Sisodiya cited was epilepsy.
“When the temperature at night is elevated,” he said, “many people find they can't sleep properly. If you can't sleep properly, then, for some people with epilepsy, that can increase the number of seizures they have.”
A 2023 paper published in Health Science Reports that was not reviewed by Sisodiya’s team found those minor disruptions can impact almost everyone’s mental health: “High temperatures can increase discomfort, interfere with sleep, and alter daily routines, potentially leading to an escalation in stress, anxiety, and even cognitive impairment if unattended.”
But while some consequences won’t outlast a given heat wave, others “can prove lethal for many people,” Sisodiya said.
He cited one of the studies the team surveyed, published in 2006 by the International Archives of Occupational and Environmental Health, when saying: “In the 2003 European heat wave, around 20 percent of the excess deaths were of people with neurological conditions.” In comparison, only 10 percent of the population had a neurological disease.
Sisodiya added that the 2022 heat waves also resulted in a high proportion of heat-related deaths in the U.K. “due to neurological conditions.”
The British Office for National Statistics reported that “dementia and Alzheimer's disease was the leading cause of excess deaths in England and Wales during 2022 heat-periods.” Their figures showed the two illnesses could have represented 27 percent of excess heat-related deaths.
The mounting data has put health authorities on alert. Agencies now warn that people with dementia face additional risks in the heat.
“Dementia is a risk factor for hospitalization and death during heat waves,” the CDC said on its website. “Hot weather poses a risk for patients with severe mental illness like schizophrenia, as medications may affect temperature regulation.”
Perry cautions that climate change may go beyond agitating existing brain disease symptoms: It is likely to create more patients — at least with Alzheimer’s. “The main part of the pathology is stress responses of the brain,” Perry said.
“Heat stress,” he said, “is going to push people to convert from normal aging to Alzheimer’s disease with greater frequency.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2024. E&E News provides essential news for energy and environment professionals.