MS symptoms may vary with the season

From the Los Angeles Times:

Multiple sclerosis, a disease in which a person’s own immune system attacks the brain and spinal cord, is a lifelong problem -- but its effects can be highly seasonal, researchers say.

Between March and August, patients suffering from multiple sclerosis were two to three times more likely to develop brain lesions than during the rest of the year, according to the paper published in the Aug. 31 issue of the journal Neurology.

The scientists looked for new T2 lesions in 939 MRI exams of 44 patients, taken between 1991 and 1993. The study found that the disease’s intensity also rose in the summer months, and appeared to be linked to solar radiation (which includes sunlight), as well as temperature.

The research was unique and unlikely to be repeated, Anne Cross, a neurologist at Washington University School of Medicine in St. Louis, wrote in an editorial on the study. Because certain drugs currently taken by multiple sclerosis patients weren't readily available in the early 1990s, this data would not be complicated by the presence of those now-common medications.

Scientists trying to set up studies examining multiple sclerosis will now have to consider seasonal variability, Cross wrote.

Case in point: Say researchers conduct a study on a drug that could potentially help multiple sclerosis patients. If that study lasts just six months, from summer into winter, any positive effects may simply be due to cooling weather and less sunlight, not to the drug's effectiveness.

Cross added that the research could ultimately lead to “important clues regarding the mechanisms of disease progression in MS.”