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Summer Heat may Worsen MS Symptoms

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Multiple Sclerosis  related image Andres Rodriquez/PhotoSpin

‘Do what we can, summer will have its flies.’ ~ Ralph Waldo Emerson

Summer is traditionally a time to let your hair down, kick off your shoes and smell the flowers, but for people with multiple sclerosis (MS), the season’s higher temperatures can cause symptoms to flare.

Warmer weather, especially when it’s humid, tends to temporarily worsen MS neurological symptoms but does not cause the disease to progress, according to the National Multiple Sclerosis Foundation.

For example, some people’s vision becomes blurred when they get overheated — a phenomenon known as Uhthoff's sign. These temporary changes can result from even a very slight elevation in core body temperature (.25 to .5 of a degree) because an elevated temperature further impairs the ability of a demyelinated nerve to conduct electrical impulses, according to the MS Society.

Some people with MS may also experience more difficultly in performing mental tasks — such as following instructions, learning new information or recalling information from memory — when the weather is hot.

Scientists at the Kessler Foundation Research Center in West Orange, N.J., examined a possible link between outside temperature and the ability of people with MS to perform various mental tasks.

The researchers tested the cognitive skills of 40 people with MS and compared them with 40 people without the disease. The researchers also recorded the average outside temperature on the testing days.

The results, published early online in the March 7, 2012 edition of the journal Neurology, showed people with MS tended to perform worse when the weather was hotter. People without MS performed equally as well regardless of the outside temperature.

Although the results need further exploration, the researchers say the results are important clues for designing future clinical trials and interpreting the results. This study also confirmed previous studies suggesting people with MS should take temperature into consideration when making lifestyle decisions, such as taking a mentally-challenging college course during summer.

Previous recent research suggested that MS relapses are more likely to occur in warmer months, and some people may have more MRI-detected active MS brain lesions when temperatures climb.

The National MS Society recommends these tips for easing the effects of the summer heat:

  • Stay in an air-conditioned environment during periods of extreme heat and humidity. (If an air conditioner is needed to help minimize the symptoms of MS, the cost of this equipment may be tax deductible if the physician has written a prescription for it.)
  • Keep cooling products available such as vests, neck wraps, bandanas, etc. when exercising or participating in outdoor activity. These products should be used to cool before and after physical activity.
  • Wear lightweight, loose, breatheable clothing.
  • Icy drinks such as “slurpees” or popsicles can provide cooling temporary relief.
  • When exercising indoors, use an oscillating fan to keep from becoming overheated.
  • Opt to exercise in a cool pool where the temperature is less than 85 degrees Fahrenheit.

Lynette Summerill is an award-winning writer and Scuba enthusiast living in San Diego, CA with her husband and two beach loving dogs. In addition to writing for EmpowHER, her work has been seen in newspapers and magazines around the world.

Sources and patient information:

Heat and Temperature Sensitivity. National Multiple Sclerosis Society. Online at:

Uththoff’s sign-decreased vision with exercise. Vision Update. Dr. Jay Stockman.

Warmer outdoor temperature is associated with worse cognitive status in multiple sclerosis. Neurology March 27, 2012 78:964-968; published ahead of print March 7, 2012, Victoria M. Leavitt, James F. Sumowski, Nancy Chiaravalloti, and John DeLuca. Online at: http://www.neurology.org/content/early/2012/03/06/WNL.0b013e31824d5834.abstract?sid=4e19e5ef-6cb5-42b1-8210-ec4ca1080b80

Reviewed April 25, 2012
by Michele Blacksberg RN
Edited by Jody Smith

Add a Comment1 Comments


I can definitely see this anecdotally amongst friends and patients who have MS. They seem to labor more in the heat of summer and symptoms seem to be more pronounced. But we get real heat out here. Although humidity is fairly low.


May 29, 2012 - 1:28pm
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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.

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