The key facts

  • The number of strokes rises at temperatures above 30 °C; the share of heat-related strokes may grow from 1% to 5–8% over 20–30 years.
  • Tropical nights (above 20 °C) disrupt deep sleep, which over the long term increases the risk of stroke and dementia.
  • According to Kallweit, a walk in the forest one hour a week reduces the risk of stroke by 3% and dementia by 4%.

Climate as a risk factor for the brain

Climate change is becoming an increasingly serious threat to brain health: rising temperatures and other environmental factors increase the burden associated with neurological diseases. Neurologist Ulf Kallweit, co-chair of the working group on environmental influences at the European Academy of Neurology, told Euronews Health on the sidelines of the European Health Forum in Gastein. According to his estimates, neurological disorders — from migraines to dementia and Parkinson's disease — affect roughly one in three people over their lifetime, and together with mental disorders their global economic burden in 2019 amounted to about €1.5 trillion. In his words, warming may worsen the course of existing diseases and raise the risk of developing new ones, but this scenario is not predetermined: policymakers can reduce the risks by reducing exposure to heat and pollution and improving living environments.

Heat, strokes and sleep

One of the most obvious concerns is the link between high temperatures and stroke. The number of strokes rises at temperatures above 30 °C, Kallweit noted. By his estimate, heat-related strokes, which currently account for about 1% of all cases, could make up 5–8% in the next 20–30 years. Heat also affects the brain indirectly — through sleep: during 'tropical nights', when the temperature does not drop below 20 °C, the body does not have time to cool down, which disrupts deep sleep and recovery. 'Everyone who experienced the past summer knows that it is harder to sleep on such hot nights,' the neurologist said. According to him, prolonged sleep deprivation sharply increases the risk of stroke and dementia.

Infections and unequal risks

Warming is changing the geography of infections carried by ticks and mosquitoes; some of them affect the nervous system — for example, Lyme borreliosis can cause neurological complications. 'There is practically no malaria there yet, but perhaps in five to ten years it will affect us in southern Europe too,' Kallweit noted. Risks are distributed unevenly: children, pregnant women, older people and people with chronic diseases are especially vulnerable. Recent studies, according to the neurologist, have shown that people experiencing socio-economic deprivation have worse brain health indicators — smaller total brain volume and more signs of vascular damage. 'If in the heat you cannot afford an air conditioner, it is much harder to endure,' he stressed, adding that health is also affected by access to healthy nutrition, housing conditions and the environment.

Green spaces and urban policy

The urban environment plays a special role: noise, air pollution and stress worsen well-being, while access to green spaces can partially protect health. 'A walk in the forest of at least one hour a week reduces the risk of stroke by 3% and the risk of dementia by 4%,' Kallweit gave as an example. He urged people to spend more time in nature and protect their sleep by limiting exposure to light and noise, but stressed that individual measures alone are not enough: much depends on public policy that determines access to cool housing, quiet neighbourhoods and clean air. He proposed strengthening protection against pollution and toxic substances and rethinking building design: 'They are still strongly oriented to the south, from where sunlight comes. Perhaps in the future such architecture will have to change.'