MONDAY, Aug. 30 (HealthDay News) -- Multiple sclerosis may be more active in the spring and summer months, new research shows.
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 area.
After one year, 310 new brain lesions were found in 31 peo
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