Study shows hotter days may worsen the ability to perform mental tasks in some people with MS

Apr 12, 2012

People with multiple sclerosis often report worse symptoms when the weather is hot. A recent study concludes that hot weather may also worsen the ability to perform mental tasks in some people with MS. The research, which needs further exploration, may help people plan activities and may improve the design of future clinical trials. Victoria Leavitt, PhD, John DeLuca, PhD (Kessler Foundation Research Center, West Orange, NJ) and colleagues conducted the study with funding by the National MS Society and National Institutes of Health. The report was published early online March 7, 2012 in Neurology.

Background: Warmer weather tends to worsen many people’s neurological symptoms of MS. Recent research also suggests that relapses are more likely to occur in warmer months, and some people may have more MRI-detected active MS brain lesions during these months. This study examined a possible link between outside temperature and the ability of people with MS to perform various mental tasks.

The study: Researchers compared 40 people with MS and 40 people without MS or any other condition that might have affected the results. Each participant was tested for their ability to process a mental task and for learning and memory. The average outside temperature on the testing day was recorded. The results showed that people with MS tended to perform worse when the weather was hotter than when it was cooler. People without MS performed equally as well regardless of the outside temperature.

The investigators also examined the performance of a separate group of 45 people with MS on these same mental tasks, measured at two time points that were six months apart. The outside temperature was recorded on each testing day. Again, the researchers noted poorer performance when the outside temperature was higher on the day of testing.

Comment: This study has several implications. For one, awareness of heat-related problems with mental tasks may impact lifestyle decisions; for example, whether to take a mentally challenging college course in the summer or winter. The results also suggest that clinical trials involving people with MS should take temperature into consideration both when designing the study and interpreting the results, especially when cognitive testing is used as a treatment outcome measure.

Read more about cognitive problems related to MS

Read more about heat sensitivity in MS and ways to cope