MONDAY, Aug. 30 (HealthDay News) -- Multiple sclerosis may be
more active in the spring and summer months, new research
In a study using MRI scans to detect brain lesions tied to MS,
researchers from Brigham and Women's Hospital in Boston found that
new lesions occurred two to three times more often in the spring
and summer compared to colder times of the year.
"We found significantly increased levels of disease activity, as defined by new T2 lesion occurrence, during the spring and summer seasons," the study authors wrote in the Aug. 31 issue of Neurology.
About 400,000 people in the United States have MS, according to
the National Multiple Sclerosis Society (NMSS), and as many as 2.1
million people may be affected by the illness worldwide.
The exact cause of MS is unknown, but it is believed to be an
autoimmune disease. That means the body's immune system mistakenly
turns on itself and damages or destroys healthy cells instead of
diseased ones. Both genetic and environmental factors are believed
to play a role in the development of the disease. Environmental
factors that have been implicated include geography and vitamin D,
a nutrient that is primarily manufactured by the skin when it comes
into contact with sunlight.
In general, more cases of MS occur the farther you get from the
equator, according to the NMSS. People with lower levels of vitamin
D may also be more at heightened risk of developing MS.
The current study included 939 brain scans from 44 people with
MS from the Boston area. At the time of the study (1991 through
1993), the volunteers weren't receiving any treatment for MS. Each
person had an average of 22 scans during the study period.
The researchers also collected information on daily
temperatures, solar radiation and precipitation for the Boston
After one year, 310 new brain lesions were found in 31 people.
The remaining 13 study volunteers didn't develop new lesions during
They found that from March to August, the occurrence of new
lesions was two to three times as high versus the fall and winter
months. They also found that warmer temperatures and solar
radiation were associated with more disease activity. Rainfall was
not associated with new lesions.
"The environment has, for many decades, been implicated in MS, especially in the development of the disease. Now, here's another piece of evidence," said Dr. Anne Cross, a professor of neurology at the Washington University School of Medicine in St. Louis, and the co-author of an accompanying editorial in the same issue of the journal.
"The big question, of course, is if spring and summer are the times these new lesions appear, what are some of the possibilities behind this?" said Nicholas LaRocca, vice president of healthcare delivery and policy research for the NMSS.
For example, he said, since heat has an effect on the symptoms
of MS, perhaps warmer temperatures might have an effect on disease
"The other intriguing issue is that while new lesions are likely to appear in the spring and summer, that doesn't mean a causal agent is operating at that time. It could be something going on prior to those seasons that takes a longer time to manifest. In the fall and winter, there is less exposure to ultraviolet light, so there's less vitamin D. Also, in the fall and winter, there is greater exposure to viral infections. Or, maybe it's dietary. People may eat different things in different seasons," LaRocca said.
He added that this study will generate new research ideas and
may provide additional clues about the cause of MS.
For people living with MS, Cross suggested making sure that your
vitamin D levels are within range throughout the year, and to get
an inactivated flu vaccine each year (that means a shot, not the
LaRocca said that during the warmer months, people with MS are
likely already taking steps to avoid the heat because warmer
temperatures can exacerbate their symptoms. It's helpful to
"develop strategies to cope with the warm weather," he said. "Make
sure you have air conditioning and try to avoid significant
activity during the warmer parts of the day."
Read more about the possible causes of multiple sclerosis from
National Multiple Sclerosis Society.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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