How Europe's Heatwaves Affect Migraine, MS, Epilepsy and Stroke

Extreme heat can trigger migraine, temporarily worsen old symptoms in people with MS or a previous stroke, and disrupt the routines that protect people with epilepsy. As Europe becomes warmer, neurological care must also begin to adapt.

I live on Mallorca, where the sea is usually one of the ways we escape the heat….

You walk into the water, expecting that first moment of relief, you know, that small physical shock as the body meets something cooler than itself.

But this summer, the Mediterranean feels different. The water around the island has been exceptionally warm. At times, entering the sea has felt less like cooling down and more like stepping into another version of the air. The water is so warm, that you can’t help sensing a lingering sensation that something is off….

At the same time, a wildfire is burning on the Spanish mainland, close to where my sister in law lives.

Somewhere between the warm sea here and the fire near someone I love, climate change has stopped feeling like a future we are discussing. It feels like a present we are already living inside.

Europe is warming more than twice as fast as the global average. But what does that mean for a brain already living with neurological disease?

Can heat trigger migraine?

Heat can contribute to migraine attacks in some people, although temperature is rarely the only factor.

A heatwave also brings glare, dehydration, altered meals and nights during which sleep becomes shallow and fragmented. Wildfire smoke may add another burden. Research on weather and migraine is not entirely consistent, but many patients recognise that their threshold changes during hot weather.

Perhaps the useful question is not simply whether heat causes migraine.

It is what happens during the heat that makes one particular brain more vulnerable.

For one person, it is the light reflected from the sea. For another, it is the loss of sleep. For someone else, it is the afternoon in the sun followed by a delayed meal and the realisation that they have barely had anything to drink.

The answer may suggest what can be protected. Regular fluids. Meals and sleep. Time outdoors during cooler hours. Sunglasses when glare is a problem. Acute medication kept available.

The aim is not to avoid summer. It is to prevent migraine from gradually taking possession of it.

Can heat cause an MS pseudoskov?

Heat can temporarily worsen previous symptoms in people with multiple sclerosis. This is known as Uhthoffs phenomenon and is sometimes called a pseudoskov.

A relatively small rise in body temperature can make conduction through previously demyelinated nerve fibres less efficient. Vision may blur. A leg may feel heavier. Fatigue, altered sensation, weakness or cognitive difficulties may return.

For someone who remembers these symptoms from a previous relapse, this can be frightening.

But Uhthoffs phenomenon does not in itself mean that new inflammatory damage is occurring. The symptoms usually improve as the body cools.

Usually is an important word.

New symptoms, symptoms that are clearly different, or symptoms that do not improve after cooling should not automatically be attributed to heat.

Cooling strategies can help, but advice to "stay cool" also exposes an uncomfortable inequality. It is easy to recommend air conditioning. It is more difficult if someone cannot afford it, cannot adapt their workplace or lives in a home that remains hot throughout the night.

Can old stroke symptoms return during a heatwave?

People who have previously had a stroke can experience a temporary return or worsening of their old neurological symptoms. This is known as post stroke recrudescence.

It may occur when the brain and body are placed under physiological stress. Recognised triggers include infection, fever, low blood pressure, disturbed sodium levels, poor sleep and emotional stress. During a heatwave, dehydration and exhaustion may contribute to several of these at once.

A hand that had recovered may feel clumsy again. Speech may become less clear. An old weakness may briefly return.

The symptoms can improve when the underlying trigger is corrected. But it is not safe to assume that this is what is happening.

A new stroke can resemble the old one. Sudden weakness, facial asymmetry, speech difficulty, loss of vision or severe imbalance require urgent medical assessment, even if the symptoms are familiar and even if the day is exceptionally hot.

Sometimes the most dangerous explanation is the one that seems familiar enough to dismiss.

Does heat affect epilepsy?

Ambient heat alone is not a proven seizure trigger for most people with epilepsy.

The things that heat disrupts may be more important.

Hot nights interfere with sleep. Summer routines make medication easier to forget. Sweating and inadequate fluid intake can lead to dehydration. Medication may be damaged if left in direct sunlight or in a hot car.

None of these factors guarantees that a seizure will occur. But several small disruptions may remove layers of protection at the same time.

Much of the practical advice is therefore ordinary. Take medication at the usual time. Check how it should be stored. Drink regularly. Protect sleep as far as possible.

Medicine sometimes underestimates ordinary precautions because they do not feel sophisticated. Yet they are often where prevention begins.

Can heatwaves and wildfires cause anxiety?

Extreme heat, wildfires and the continuing threat of climate change can contribute to anxiety, psychological distress and disrupted sleep.

Climate anxiety is sometimes discussed as though it were simply an irrational fear requiring reassurance.

But when the sea is exceptionally warm and a fire is burning close to someone you love, anxiety may be a proportionate response to something real.

The difficulty begins when vigilance becomes impossible to switch off. When every hot day feels like a warning. When the future becomes difficult to imagine without fear.

Stress and sleep loss can also affect migraine and epilepsy and make the symptoms of many neurological conditions harder to manage. The climate outside us can, in this way, begin to change the neurological climate within us.

Perhaps the answer is neither dismissal nor despair, but agency.

Neurological care in a warmer Europe

We need to prepare for a future with more heatwaves, hotter nights, wildfires and poor air quality.

People with neurological and other chronic diseases must be included in heat plans. Patients need advice before the temperature rises. Homes, hospitals and care facilities need access to cooling. Medication, clean air and healthcare must remain available during fires and evacuations.

But adaptation alone is not enough.

We must also reduce the greenhouse gas emissions driving global warming. Otherwise, adaptation becomes an attempt to keep moving the boundary of what we expect people to endure.

As doctors, we are trained to treat what is in front of us. A migraine attack. An MS pseudoskov. The return of old stroke symptoms. A seizure after several sleepless nights.

Prevention asks us to look further upstream.

If global warming is worsening symptoms, increasing health risks and restricting the lives of our patients, climate action is not separate from healthcare.

It is part of healthcare.

Today, for me, climate change is the unusually warm sea outside my home on Mallorca and a fire burning close to someone I love on the mainland.

For someone else, it is the leg that becomes heavier before the afternoon is over. The night of sleep that never comes. The old symptoms that suddenly return.

We need to prepare for this future because part of it has already arrived.

But how difficult that future becomes is still, at least partly, a decision we are making now.