Sibling exposure reduces multiple sclerosis risk

Reported by Susan Aldridge, PhD, medical journalist

Having higher exposure to infant siblings during the first six years of life is linked to a lower risk of multiple sclerosis, according to a new study.
There has been much interest in the 'hygiene hypothesis' of disease. That is, those who are not exposed to common infections in childhood are more likely to develop allergic or autoimmune disorders like asthma.

Having brothers and sisters increases the likelihood of exposure to infection. A team at the Menzies Research Institute, Hobart, Australia, have studied a group of 136 people with multiple sclerosis (MS) - a disease thought to have a strong auto-immune component. They compared them with a group of healthy controls, with respect to their exposure to siblings in early life.

Increasing duration of contact with a younger sibling aged less than two years in the first six years of life led to decreased risk of MS. One to three years of contact reduced the risk by 43 per cent, three to five years reduced it by 60 per cent. And if the contact was more than five years, the risk was reduced 88 per cent. Tests also showed altered immune responses with exposure to infant siblings. Further work is now needed to determine how childhood exposure to infection and its effect on the immune system govern the risk of MS.

Source
Journal of the American Medical Association 26th January 2005 Volume 293 pages 463-469

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