MS more active in spring and summer: study

The neurological disease multiple sclerosis can be more active in the spring and summer, according to a new study that detected brain lesions two to three times more frequently in warmer months.

"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," said study author Dominik Meier of Brigham and Women's Hospital in Boston.

Researchers compared brain scans of 44 patients with untreated MS which were taken from 1991 to 1993 to weather data from the same period.

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.

Some 310 new lesions were found in 31 of the patients over the course of a year while 13 patients did not develop new lesions during the study.

The weather data included daily temperature, solar radiation and precipitation measurements for the Boston area.

"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," Meier said in a statement.

There was no link found between precipitation and lesions.

MS is a chronic and often disabling disease which attacks myelin, the fatty substances that surround and protect the nerve fibers in the central nervous system.

When the myelin is damaged, it forms scar tissues -- or sclerosis. This damage distorts and interrupts nerve impulses traveling to and from the brain and spinal cord.

Some symptoms will come and go, while others will be chronic and often include fatigue, numbness, balance and coordination problems, spasticity, pain, dizziness, and emotional changes.

The cause of MS is still not known, but researchers believe it is an autoimmune disease which can be affected by genetic and environmental factors, according to the US-based National Multiple Sclerosis Society.

MS is known to occur more frequently in areas that are farther from the equator and some scientists think it could have something to do with a lack of vitamin D, which the body produces naturally when the skin is exposed to sunlight.

MS affects about 2.5 million people worldwide, including about 400,000 in the United States.

The study was published Monday in the journal Neurology.

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