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Higher MS Activity Associated With Warmer Seasons

Multiple sclerosis prevalence and severity appear to increase during summer and spring

TUESDAY, Aug. 31 (HealthDay News) -- Multiple sclerosis (MS) activity -- both incidence and severity -- appears to be higher in the spring and summer, according to research published in the Aug. 31 issue of Neurology.

Dominik S. Meier, Ph.D., of Brigham and Women's Hospital in Boston, and colleagues assessed disease activity, in the form of new lesions detected by serial T2-weighted magnetic resonance imaging (MRI), in 939 brain MRI scans taken from 44 untreated MS patients from 1991 to 1993. The researchers looked at weather activity during the same time period.

The researchers found that T2 activity -- as opposed to attacks or contrast enhancement -- showed a two to three times higher likelihood of new lesions forming during March through August than the rest of the year. Disease intensity, too, was higher during summer. Solar radiation in particular was found to be related to disease activity. For progressive MS, the elevated risk season appeared to lessen and to happen about two months earlier.

"This study documents evidence of a strong seasonal pattern in subclinical MS activity based on non-contrast brain MRI. The observed seasonality in MS disease activity has implications for trial design and therapy assessment. The observed activity pattern is suggestive of a modulating role of seasonally changing environmental factors or season-dependent metabolic activity," the authors write.

Three authors disclosed financial relationships with pharmaceutical and/or medical device companies.

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