Climate change exacerbates neurological diseases and mental health disorders as world heats up: Study

Climate change’s impact on health has been well studied, particularly when it comes to infectious and respiratory diseases. But it also takes a toll on neurological health, with the body’s temperature regulation process appearing to be a key driver in the uptick of conditions triggered by extreme heat.

“In order to work properly, the brain has to be maintained within a relatively narrow temperature range,” said Sanjay Sisodiya, a professor at the UCL Queen Square Institute of Neurology who led the research. “If the brain has a disease, then the brain’s ability to thermoregulate is compromised. Take someone with a neurological disease and put them in an extraordinary heat wave, you can see how that could well make their neurological disease worse.”

More investigation is needed into the exact mechanism linking neurological disorders with higher temperatures, Sisodiya added. As extreme weather worsens and becomes more common, it’s increasingly vital to untangle the exact relationship, particularly for the youngest, oldest and most vulnerable populations.

For the new study, the researchers reviewed 332 reports looking at environmental impacts on 19 neurological conditions with the highest disease burdens, including Alzheimer’s and other forms of dementia, migraine, stroke, multiple sclerosis and meningitis. They also gathered research on depression, anxiety and schizophrenia as psychiatric disorders have frequent comorbidity with neurological diseases. The findings show weather impacts each disease in distinct ways, but most conditions are broadly associated with higher prevalence and worsened symptoms.

Among their findings are that people with Alzheimer’s and other dementias struggle to make adaptive choices in extreme heat such as seeking assistance, wearing lighter clothing and drinking more water. Hotter weather is also likely to lead to more fatal or disabling strokes and can impact epilepsy, which is made worse by sleep deprivation. High nighttime temperatures are a hallmark of climate change and can impact sleep patterns. (The research also found that extreme cold can take a toll on health as well.)

Incidence mental health disorders along with hospitalization and risk of death were associated most strongly with increased ambient temperature. One report surveyed in the new study showed that US health insurance claims on mental health-related emergency room visits between 2010 and 2019 increased on days with extreme heat. Extreme weather events such as storms and wildfires can trigger acute cases of anxiety, post-traumatic stress, depression and suicidal ideation.

The brain’s response to a warming climate causes damage that can go undetected until far after medical intervention would be effective, said Burcin Ikiz, a neuroscientist who studies the impact of environmental patterns on the brain. When heat rises, she said “our brains go into a stress response” that can translate into inflammation and other forms of degeneration that impact cognitive health.

“What scares me most about this scenario is that by 2050, not only will we see an explosion of people with neurological disorders, but it will happen in our 40s and 50s instead of 70s and 80s because our brains are bombarded by different stresses like heat, pollution and microplastics,” added Ikiz, the founder and chair of the International Neuro Climate Working Group, an initiative to promote more research and advocacy around climate change’s threat to the brain.

Sisodiya and Ikiz called for more research and policy intervention to mitigate the economic toll climate change will take on individuals and public health systems, particularly in poorer countries. As the world faces another round of record-breaking summer heat, though, individuals can also take steps to guard against extreme heat.

“We need to stop burning fossil fuels, stop putting emissions into the air,” Sisodiya said. “But beyond that, we can make sure that the weather alerts are appropriate, are informative, that people can act on them and know to take simple measures like staying out of the sun during the peak hours of exposure, keeping windows or shutters closed, using things to keep cool and hydrated, [and having] an adequate supply of medication.”