Climate Change Is Bad for Our Brains

Climate change is intensifying the symptoms of some brain conditions, according to our new review. Stroke, migraines, meningitis, epilepsy, multiple sclerosis, schizophrenia, Alzheimer's disease and Parkinson's are among the conditions that may deteriorate as temperatures and humidity increase.

Our brains manage the environmental pressures we encounter, including greater heat and humidity. They do this, for instance, by initiating sweating and prompting us to leave direct sunlight for the shade.

The billions of neurons in the brain each resemble a computer that learns and adapts, containing numerous electrically active elements. Many of these elements operate at varying speeds according to the surrounding temperature, and are built to function together only within a limited temperature range.

Our bodies and all their systems perform effectively within these boundaries, to which humans have adapted over thousands of years.

Humans originated in Africa and tend to be comfortable at temperatures from 20°C to 26°C and humidity levels of 20% to 80%. Indeed, many parts of the brain already function near the upper end of their temperature limits. Even modest rises in temperature or humidity can therefore prevent them from working together as effectively.

When environmental conditions quickly shift beyond familiar ranges, as they are doing through climate change-related extremes of heat and humidity, the brain finds it harder to control body temperature and starts to function less well.

How climate change affects the brain

Certain diseases can already interfere with sweating, which is vital for staying cool, or with recognising that we are overheating. Some medicines prescribed for neurological and psychiatric conditions add to the difficulty by impairing the body's response: they may reduce sweating or disrupt the temperature-regulating mechanisms in the brain.

Heatwaves aggravate these effects. They can, for example, interrupt sleep, while poor sleep worsens conditions including epilepsy.

Heat can also make defective brain wiring function even less effectively, explaining why people with multiple sclerosis may experience more severe symptoms in hot weather. Meanwhile, dehydration during heatwaves can thicken the blood and make clotting more likely, resulting in strokes.

Climate change will therefore affect many people with neurological diseases, frequently through several pathways at once. As temperatures climb, hospital admissions for dementia become more frequent.

In epilepsy, seizure control may decline; multiple sclerosis symptoms can worsen; and stroke rates increase, alongside more deaths linked to stroke. Many widespread and serious psychiatric conditions, including schizophrenia, also deteriorate, with higher rates of hospital admission.

During the European heatwave of 2003, people with neurological conditions accounted for approximately 20% of the excess deaths.

Temperature extremes that are unusual for a location, greater-than-normal changes in temperature during the day, and damaging weather events such as heatwaves, storms and floods can all exacerbate neurological conditions.

Heatwaves, cities and neurological diseases

Specific circumstances add further complexity. For instance, the warming effect of urban areas and a shortage of green spaces can heighten the damage that heatwaves cause to neurological and psychiatric diseases.

The number of people globally with neurological and psychiatric conditions that may be harmed by climate change is vast. Around 60 million people worldwide have epilepsy. About 55 million people globally live with dementia, and more than 60% of them are in low- and middle-income countries.

As the global population grows older, this figure is expected to rise to more than 150 million by 2050. Stroke is the world's second-leading cause of death and one of the leading causes of disability.

Offering help

The wider necessity of addressing climate change is unmistakable. Governments must introduce mitigation measures now, coordinated internationally.

However, meaningful results from serious action will take years to emerge. Until then, people with neurological diseases can be supported with information tailored to the dangers posed by severe weather events and temperature extremes.

Doctors and public health specialists can advise people on lowering these risks. Local weather-health warning systems can be adapted for neurological diseases. It is also possible to work with affected people, their families and carers so that weather-health alerts and responses are appropriate for their communities and practical to put into effect.

If climate change is not addressed within neurological care, the gains from current scientific advances could be lost. Above all, neurological diseases reveal what may happen when a healthy brain is pushed past the limits shaped by evolution and beyond its capacity to adapt behaviourally.

This prospect becomes more probable as we continue to fall short in tackling climate change. To keep living as we wish, we need to pay closer attention to the feeling that it is becoming too hot and take action on climate change. We rely on our brains, and climate change harms them.

Sanjay Sisodiya, Professor of Neurology, UCL and Mark Maslin, Professor of Natural Sciences, UCL

This article is republished from The Conversation under a Creative Commons licence. Read the original article.