Why People with Multiple Sclerosis Don't like Warm Weather

There's little doubt that the weather outside affects how we feel. Who doesn't feel a little down when the clouds hide the sun and it's cold and gray outside? For people with multiple sclerosis, the weather even affects their ability to think and remember. People with multiple sclerosis experience more "brain fog" and cognitive issues when the temperatures climb.

Brain Fog, Multiple Sclerosis and Warm Weather

When researchers tested 40 people with multiple sclerosis to see how quickly they processed information and remembered, their performance varied with the temperature. When it was cooler outside, they performed 70% better on these tests than when temperatures were warm.

Surprised that temperature could have such an impact? Most multiple sclerosis patients wouldn't be. Many say their symptoms are worse in warm weather. When they become overheated, up to 60% of M.S. patients develop "paroxysmal" M.S. symptoms including transient numbness, tingling, weakness, dizziness, blurred vision, extreme fatigue or brain fog. These symptoms are called paroxysmal, because they're usually short-lived and aren't an indication of a relapse. They generally subside once their body temperature returns to normal.

Heat intolerance was once used to make the diagnosis of M.S. before there were MRI machines to look for plaques in the brain and spinal cord. Doctors would immerse a suspected M.S. sufferer in a tub of very warm water to see if it brought on neurological symptoms. If so, they were presumed to have multiple sclerosis.

What Causes Cognitive Issues and Brain Fog When the Temperature Rises in M.S?

People with multiple sclerosis have patchy areas on nerves in the central nervous system and spinal cord where the myelin sheath that insulates the nerve has worn away. When people with multiple sclerosis become overheated, these damaged nerve fibers can't conduct impulses as well. In people who have M.S. with heat intolerance, even modest rises in body temperature can bring on symptoms - including cognitive issues and brain fog.

Multiple Sclerosis Symptoms and Heat

What does this mean? People with multiple sclerosis who experience heat sensitivity may feel more comfortable living in a cooler environment so they won't have to deal with summer heat, heat intolerance, brain fog and cognitive issues. It's a simple lifestyle change that can make a big difference for a person with multiple sclerosis.

References:

Eurekalert.org. "Warm Weather May Hurt Thinking Skills in People with MS"

Merck Manual. Eighteenth edition. 2006.