Brain Health Compromised by Climate Change

Climate change will continue to affect brain health, researchers predicted.

“The scale of potential effects of climate change on neurological diseases is likely to be substantial,” wrote epilepsy researcher Sanjay Sisodiya, PhD, of University College London, and co-authors in a Lancet Neurology essay.

In a review of 332 articles that spanned several decades, Sisodiya and colleagues found that the incidence, prevalence, and severity of many neurologic conditions were affected by climate change.

In some countries, including the U.S. and South Korea, rising temperatures and humidity extremes were associated with higher ischemic stroke incidence, they reported. In other countries, cold periods upped the risk of intracerebral hemorrhage.

Multiple sclerosis patients reported worse symptoms when temperatures were higher than the long-term average, they added. Migraine admissions to the emergency department rose when days were hotter. Regional climate-related conditions have been associated with tick-borne encephalitis and mosquito-borne infections, and in several countries, Alzheimer’s- and dementia-related hospital admissions increased when temperatures climbed.

Climate shifts that affected neurologic disorders included both low and high temperature extremes and large temperature fluctuations within a day, the researchers reported.

The impetus for the review came from “listening to the experiences of people with severe epilepsies and their families and carers during heatwaves, combined with existing concerns about the environment,” Sisodiya told MedPage Today. “I started asking questions and realized that the changing climate could have serious negative implications for people with neurological conditions.”

The research team studied the neurologic conditions most burdensome across the world, starting with stroke, to see how ambient temperature may have affected the nervous system.

“Climate change has pervasive, systemic consequences,” Sisodiya and co-authors wrote. Rising temperatures challenge the capacity to maintain body temperature, they pointed out. Heat can also have direct effects on molecular function, particularly ion channels, they added.

“Neurological diseases, and their treatments, can undermine all aspects of thermoregulation: for example, they can compromise adaptation to long-term rising temperatures and acute temperature elevations (e.g., in heatwaves),” the researchers wrote. “Conversely, disease pathophysiology can itself be aggravated by normal thermoregulatory responses.”

Importantly, high temperatures at night can affect sleep, and compromised sleep can aggravate underlying neurologic conditions like epilepsy, Sisodiya said.

Relatively few robust investigations about the neuro-specific effects of climate change have been conducted, noted Larry Junck, MD, of the University of Michigan in Ann Arbor, and co-authors in an accompanying editorial.

“Perhaps because some physicians erroneously regard the issue as political, the medical profession has grossly overlooked the need to teach physicians and medical scientists about the health harms of climate change, and medical researchers and funding sources have not been adequately motivated to research this topic,” Junck and colleagues wrote.

A scoping review published in Neurology in 2023 evaluated extreme weather events and temperature fluctuations, emerging neuroinfectious diseases, and the effects of pollution on neurologic disorders, the editorialists said.

“We believe that air pollution should be considered together with climate change because the dominant cause of both is the burning of fossil fuels,” Junck and co-authors wrote. “Few neurologists are aware of the importance of exposure to PM 2.5 (particulate matter with a diameter of less than 2.5 μm) from fossil fuels as a major risk factor for stroke, accounting for about 20% of stroke incidence, mortality, and morbidity.”

Many neurologists are unaware that air pollution has been linked with dementia and Parkinson’s disease, they added.

Overall, the studies showed broad and complex adverse effects on the nervous system, especially at temperature extremes to which people are unaccustomed, Sisodiya noted. Few projected the future effects of climate change on brain health, which could hinder policy development, he added.

“We need to be thinking about and researching the possible effects of climate change on people with neurological diseases, and putting in place appropriate, effective adaptation measures,” Sisodiya said. “We need more data, but there’s enough to raise serious concerns and to act now.”

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