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 activity.
"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 inhalable vaccine).
All rights reserved