While most people don’t look forward to the gray chill of wintertime, those with multiple sclerosis (MS) can take heart. A new study reveals something many people with the condition already know: MS brains work better in colder weather.

Using functional magnetic resonance imaging (fMRI), Kessler Foundation researchers measured blood flow to the brain and found that people with MS had a more difficult time performing tasks that required thinking during warmer months.

That heat has a dramatic effect on those with MS is nothing new. Wilhelm Uhthoff first observed impaired vision in MS patients after hot baths and exercise in 1890, and the “hot bath” test became a diagnostic tool for MS for much of the next century.

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“What’s missing from [research addressing heat and cognition in MS] until now,” explains Dr. Victoria Leavitt, a research scientist in neuropsychology and neuroscience at the Kessler Foundation and lead investigator on the study, “is what’s happening to people with MS on a day to day basis in the real world, outside of experimental manipulation." 

Hot and Bothered

In an earlier study, Leavitt and her team set out to demonstrate a link between temperature and impaired brain function. They used test results culled from their database of previous MS studies and cross-matched the dates they were conducted with the records of outdoor temperatures on those days.

Intrigued by their results, Leavitt and her team wanted to learn why the change in temperature affects people with MS but not those who are healthy. Using fMRI, they were able to watch the MS brain in real-time as people performed cognitive tasks.

Twenty-eight MS patients were given an fMRI scan, and researchers measured outdoor temperature on the days they were scanned. While undergoing the fMRI, patients were shown a series of letters and asked to press a button when they saw the target letter they were looking for. This simple task proved more challenging for the volunteers during warmer months.

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An important way to use this research, said Leavitt, “[is to look] at the effects of medication on cognition.” There are no current drugs available to address cognitive problems in MS, but that is changing as cognitive impairment is recognized as a significant symptom in people with MS.

In testing a drug to improve cognition, for example, a test given in summertime may show skewed results purely because of the outdoor temperature. “You might be obscuring the effects of the drug that are actually there,” cautions Leavitt.

Move North?

Moving farther away from the equator seems like a no-brainer, but a chillier climate comes with drawbacks of its own. Some patients report increased spasticity, and there is a documented risk of seasonal affective disorder (SAD), a type of depression.

Even if one climate might be more MS-friendly than another, pulling up roots is not the answer. Instead, experts say there are many ways to manage the seasonal MS symptoms that affect you most.

If you make your home in a hot climate, stay indoors in the AC during the hottest part of the day and avoid raising your core temperature with hot showers or baths.

If you live where it’s cold, don’t crank up the central heat. Instead, keep the room cool, layering your clothing so you can adjust your core temperature quickly.

Cool showers and cold drinks, or even a cooling vest, can help, especially before tasks that require extra cognitive efforts. Avoiding a heat-induced brain fog is especially important for those who drive often or have dangerous jobs, who especially need to keep a cool head.