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Month of Birth Influences MS Risk

Those born in May face highest risk, while those born in November face lowest, study says

TUESDAY, Dec. 7, 2004 (HealthDayNews) -- Your month of birth may influence your risk of multiple sclerosis, says a study published online in the British Medical Journal.

The study concluded that people in the northern hemisphere who are born in May have an increased risk of developing MS later in life, while those born in November have the lowest risk. Complex interactions between genes and an infant's environment before and shortly after birth may account for this association, the study authors suggest.

Researchers analyzed data on 17,874 Canadian and 11,502 British patients with MS. The study found that far fewer Canadians with MS were born in November. The same was true in the United Kingdom, where the number of MS patients born in December was also much lower. Significantly more of the British MS patients were born in May.

The researchers then added data about Danes and Swedes with MS to the Canadian and British data. The overall results showed a 13 percent increased risk of MS for people born in May compared with November, and a 19 percent decreased risk for people born in November compared with May.

The authors said their findings show the association between the month of birth and the risk of MS in northern countries. They contend that the study lends support to theories that environmental factors before and immediately after birth affect the development of an infant's nervous or immune system, thereby influencing the risk of MS in adulthood.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about multiple sclerosis.

SOURCE: British Medical Journal, news release, Dec. 7, 2004
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