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A study conducted in London found that babies born in May have significantly lower levels of vitamin D and a potentially greater risk for developing MS than babies born in November. Multiple sclerosis is a disabling neurological condition that can lead to problems with vision, muscle control, hearing and memory.
The study involved cord blood samples taken from 50 babies born in November and 50 more samples taken from babies born in May between 2009 and 2010. The samples were collected in London, where the "month of birth" effect is particularly evident. Previous studies suggested the risk of MS is highest for people born in May and drops for those born in November, the study authors noted.
The blood samples were analyzed to assess levels of vitamin D and white blood cells involved in the body's immune response. White blood cells are capable of attacking the body's own cells, as they do in MS, the researchers said.
The study found that May babies had vitamin D levels roughly 20 percent lower than babies with November birthdays. The May babies also had roughly double the level of potentially harmful autoreactive T-cells than the November babies.
"By showing that month of birth has a measurable impact on in utero immune system development, this study provides a potential biological explanation for the widely observed 'month of birth' effect in MS," study co-author Dr. Sreeram Ramagopalan, a lecturer in neuroscience at Barts and The London School of Medicine and Dentistry at the Queen Mary University of London, said in a university news release.
"Higher levels of autoreactive T-cells, which have the ability to turn [against] the body, could explain why babies born in May are at a higher risk of developing MS," he added.
Because vitamin D is formed when skin is exposed to sunlight, the birth-month effect is viewed as evidence that vitamin D levels during pregnancy play a role in MS risk, the study authors said in the news release.
"The correlation with vitamin D suggests this could be the driver of this effect," said Ramagopalan. "There is a need for long-term studies to assess the effect of vitamin D supplementation in pregnant women and the subsequent impact on immune system development and risk of MS and other autoimmune diseases."
The study uncovered an association linking birth month to vitamin D levels and MS risk. It did not prove cause-and-effect.
-- Mary Elizabeth Dallas
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