Heat waves and rising global temperatures are amplifying health risks beyond ecosystems, biodiversity, and water resources. They are contributing to a higher incidence of illnesses that affect people worldwide. A comprehensive review from the Cleveland Clinic in Ohio examined 364 studies dating from 1990 onward, linking increasing temperatures and extreme weather events to greater risks of stroke, dementia, and multiple sclerosis. The findings also highlight that even milder ailments such as headaches are more common in warmer conditions.
Previous scientific work has shown that longer summers and higher heat stress the human body. The body must work harder to cool itself and to circulate blood to vital organs. Inhaled pollution and heat together can stress the body, potentially elevating the risk of brain disorders and other neurological conditions.
Lead author Dr. Andrew Dhawan of the Cleveland Clinic noted that climate change presents many challenges that warrant deeper study. As the effects of a warming planet on human health become clearer, neurologists are urged to anticipate how neurological diseases may evolve and respond to these changes.
The brain shrinks when dehydrated
Warmer climates drive the body to lose more water through sweat, increasing the risk of dehydration. Even mild dehydration can trigger headaches and migraines. When the brain lacks adequate hydration, it can contract slightly and pull away from the skull, placing pressure on nerves and causing pain, according to the Cleveland Clinic.
One study found that a higher average temperature on the day prior to hospital admission was associated with a 7.5 percent rise in headaches. A broad review of 364 studies on adults published between 1990 and 2022 looked at how health problems relate to temperature changes, extreme weather, and air pollution.
Extreme weather and temperature shifts have been linked to more frequent and severe strokes, increased migraine activity, dementia hospitalizations, and worsening multiple sclerosis symptoms. Climate change has created more favorable conditions for diseases affecting the nervous system such as meningitis, encephalitis, and polio, which can bring new populations into contact with these illnesses. Vector-borne risks from animals and insects, including West Nile virus, meningococcal meningitis, and tick-borne encephalitis, have grown as temperatures rise. Tick and mosquito-borne infections have also increased with warmer weather.
The study did not specify why dementia or multiple sclerosis might worsen with climate change, but age appears to be a factor. Older adults are generally more susceptible to heat-related illness, and many live alone or may not stay adequately hydrated.
Heat worsens multiple sclerosis
Outdoor temperature fluctuations place extra strain on the brain, potentially accelerating processes linked to dementia and other neurological conditions. In multiple sclerosis, heat can slow nerve signals and temporarily worsen symptoms. If global temperatures continue to rise, these effects may persist or intensify.
Research involving more than three million Medicare patients showed that a 1.5°C temperature rise was associated with a 12 percent increase in dementia-related hospitalizations. In another study, a five-degree rise correlated with a higher risk of all headache types, especially nonmigraine headaches, among more than 22,000 emergency room visits for headache symptoms.
The reasons behind these changes remain unclear, though researchers have proposed several possibilities. They point to temperature shifts, ecosystem strain, greater air pollution exposure, and food insecurity as potential contributors. The body registers heat as stress, and pollutants can enter the bloodstream, aggravating respiratory and brain health alike.
Further research is needed on ecosystem stability and food security, as well as how climate-related pollution may age brain arteries. A warming climate can lead to stagnant air and higher pollutant levels that harm lung and nerve health. Some fine particles in the air can affect skin and contribute to aging signs such as brown spots and wrinkles, underscoring broader health effects from air quality. In Africa, the meningitis belt has shown that dust particles carried by Harmattan winds can heighten transmission, and floods in Europe have been linked to spikes in encephalitis and tick-borne illnesses. These associations underscore the diverse channels through which climate change can influence brain and nervous system health.
One limitation of the review is that most studies were conducted in affluent nations, so applying the results to lower-income regions should be done with caution. Recent analyses indicate that extreme weather events are increasing, with a large portion of U.S. states experiencing damaging air-related events in the last decade. These observations emphasize the need for ongoing surveillance and research across varied settings.
Reference work: Neurology Journal, early online release from 2022. The exact article details can be found in the cited journal issue for readers seeking fuller context and data.
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Note: The environment department will not publish contact information here. All content reflects the summarized findings from the cited clinical literature and is presented for informational purposes only.