August 31, 2010
Multiple Sclerosis Activity Changes With Seasons
(Ivanhoe Newswire) -- Multiple sclerosis (MS) appears to be heavily impacted by environmental factors, and activity increases during spring and summer months.
One significant aspect is that clinical trials often use MRI to assess the effectiveness of a drug, and studies commonly last from 6 to 12 months. If the study ran from fall to spring, it might appear that lesions decreased due to drug effect, but the cause might just be change of season. The opposite would occur if a study began in spring and lasted through the summer.
"Our results showed that the appearance of lesions on brain scans was two to three times higher in the months of March to August, compared to other months of the year," study author Dominik Meier, PhD, of Brigham and Women's Hospital in Boston, was quoted as saying.
Researchers compared MRI brain scans of 44 people, taken from 1991 to 1993, to weather data from the same time period. Participants were between the ages of 25 and 52 with untreated MS. Each person had eight weekly scans, then eight scans every other week followed by six monthly check-ups, for an average of 22 scans per person.
Weather information included daily temperature, solar radiation and precipitation measurements for the Boston area.
After one year, 310 new lesions were found in 31 people. Thirteen people had no new lesions during the study. "Not only were more lesions found during the spring and summer seasons, our study also found that warmer temperatures and solar radiation were linked to disease activity," said Meier. There was no link found between precipitation and lesions.
"This is an important study because it analyzes records from the early 1990's, before medications for relapsing MS were approved, so medicines likely could not affect the outcome.
A study like this probably won't be able to be repeated," Anne Cross, MD, of the Washington University School of Medicine in St. Louis, was quoted as saying in an accompanying editorial.
"Future studies should further explore how and why environmental factors play a role in MS."
SOURCE: Neurology, August 31, 2010