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Could Warmer Weather Hamper Brain Function in People With MS?

THURSDAY Nov. 7, 2013 -- Warmer temperatures might reduce the ability of people with multiple sclerosis to complete mental tasks and process information, new research suggests.

Although heat has long been linked to a worsening of symptoms among people with the inflammatory disease, it wasn't clear exactly how the process worked. The new study used brain-imaging technology to focus on the areas of the brain affected by rising temperatures, the researchers said.

"We found there is a correlation between outdoor temperature and levels of brain activity," said study principle investigator Victoria Leavitt, a research scientist at the Kessler Foundation in West Orange, N.J. "The amount of activity in people's brains increases when the temperature is warm, and lowers when temperatures are lower."

The researchers suggested that their findings could lead to the development of treatment strategies that may help people with multiple sclerosis (MS) cope with the effects of warmer weather on their quality of life.

The study involved 28 people with MS (26 women and 2 men) who had worse mental function on warmer days.

Using functional MRI, the researchers found that higher temperatures increased activity in certain parts of the brain -- the frontal cortex, dorsolateral prefrontal cortex and parietal cortex -- during simple mental tasks. This increase in brain activity was not seen in a comparison group of people who did not have MS.

"These areas of the brain that we've highlighted are referred to very generally as task-related areas of the brain," Leavitt said. "They are involved in our ability to multitask, or process a lot of information and apply ourselves to the most important task at any given moment." Leavitt said people with MS frequently report having trouble doing just that.

The findings were published online recently in the journal Brain Imaging and Behavior,

Another expert called the new findings "a classic example of good news and bad news."

"The study shows us the ways in which brain function is different in MS. In a way, it's nature's way of compensating for the deficits of MS," said Nicholas LaRocca, vice president of health care delivery and policy research at the National Multiple Sclerosis Society, which helped fund the study.

The good news, LaRocca said, is that when people with MS have to do thinking tasks in the presence of heat, their brain is recruiting more areas of the brain to accomplish what it needs to do. The bad news, he said, is that the brain is working in a different way than someone who doesn't have MS, so it's functioning abnormally.

Although why this happens remains unclear, LaRocca said the fact that MS compromises the central nervous system could play a role. "Physically, the ability of the nervous system to transmit impulses from one part to another has been compromised because of damage to the nerve fibers," he said.

In order to transmit electrical impulses, the body has a complex system of chemical interactions, LaRocca said. Over the course of evolution, these interactions developed in such a way that they work best within a narrow temperature range, he said. Even slight temperature changes can interfere with that natural process.

"For those with MS, the transmission of nerve impulses is already compromised, so in a sense it may not take as much to push it over the line into dysfunction," LaRocca said.

So exactly how high do temperatures need to rise before it affects brain function in people with MS? Study author Leavitt said that's another question that remains unanswered.

"Although everyone is interested in a critical cutoff point when it becomes too hot, this cross-sectional study doesn't look at how rising temperatures affect individuals, or when hot becomes too hot," she said.

Since MS is a complicated disorder that varies from person to person, there is likely no simple answer, LaRocca said. "Some people are heat sensitive, while others can tolerate it better," he said.

For people with MS who experience a worsening of symptoms when temperatures rise, LaRocca recommended some cooling strategies:

  • Wear cooling hats or garments, such as vests with gel packs inserted into them.
  • Cool the body before exercise.
  • Use air conditioning.

Although it has not been proven, LaRocca said high humidity also could be a factor since it makes it harder for the body to compensate for high temperatures.

"The bottom line is that for people with MS ... day-to-day functioning may be improved if they are able to maintain a comfortable body temperature and avoid excess heating," LaRocca said.

Going forward, Leavitt said her team will examine if the resting body temperature of people with MS is higher than normal.

More information

The U.S. Institute of Neurological Disorders and Stroke has more about multiple sclerosis.

Posted: November 2013

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