[repr0bate]

Study links birth date to MS

Babies born in May have an increased chance of developing multiple sclerosis, according to new research.

Scientists at Oxford University believe they have discovered the time of year when birth can pose the most risk of babies being struck down by MS later in life.

As a result they claim parents should plan their families carefully to avoid risk of the illness, a neurological condition which affects people in different ways.

In a paper published by the British Medical Journal, clinical neurologist Professor George Ebers, of Oxford's department of clinical neurology, said infants born in November have statistically the lowest chance of going on to develop MS.

Those born six months later had the highest chance of getting the illness.

He said explanations for the link were unclear, but past studies suggested exposure to the sun or seasonal variations in the mother's vitamin D level during pregnancy may have an impact on brain development.

Although Prof Ebers warned mothers should not start taking vitamin D supplements during pregnancy to combat MS in their child's later life, he did agree that couples planning a family may want to ensure their children were not born in May.

He said: "In cases where MS is in your family it might be a reasonable strategy to take."

Prof Ebers' study involved more than 11,500 patients in Britain and 17,800 in Canada, and looked at detailed information about each.

It found that in Canada significantly fewer people with MS were born in November compared with a control group. The same trend was found in Britain, where significantly more MS sufferers were born in May.

By widening the research to cover more than 42,000 people, using data from Sweden and Denmark, the study found a 13 per cent increase in the risk of MS for those born in May compared with November.

I saw this in my local news...sounds a little crazy to me. Can anyone with scientific knowledge verify?

[bradley]

hmmmm - presumably if it's in the BMJ, the epidemiology (statistical calculations not only measuring trends but seeing if they are statistically significant) is sound; in which case it's hard to disagree. I've never heard of this, though.

It seems strange that the first 6 months of your development could have as significant an impact as this on the risk of developing a disease much, much later in life; people are usually either genetically predisposed for high risk of degenerative diseases (does MS count as a degenerative disease? i'm assuming it does) or predisposed by lifestyle factors; what half of the year you are born in is a lifestyle factor, but that factor is only going to be relevant over 6 months; not a lifetime.... so you wouldn't expect lifestyle factors such as this having an impact.

[Iain]

Assuming the research is good, the absolute risk measure is missing. It says that the risk is increased by 13%. If the average is ten people in every 10,000 (one in a thousand) get MS, this suggests that in the danger months about 11 in 10,000 would end up with MS and in other months about 9 in 10,000. Look at it like that and it's not such a big deal.

Where the absolute risk of something happening is small, even big relative percentage increases in risk don't mean anything much at all.

(In fact, about 1 in 1500 people get MS in the USA and worldwide the figure is considerably lower than this; so 13% makes even less difference to one person's chances of getting MS than my figures above suggest).

[bradley]

it's an extra 11,200-odd MS sufferers each time spring comes around, though. That's not negligible.

more importantly, though, this study should be another clue for researchers looking to find an effective cure to MS. Let's hope it's not a red herring and can point at least one of them in the right direction.

[Iain]

Bradley,

You're right; but the thing about these studies is people always worry about whether it will happen to them (naturally enough). If you say its a 13% increase in risk, people get worried and might take lots of extra supplements or do something damaging.

If you say that the risk increases by 2 in 10,000, say, it gives a much better understanding of what the real risk is and people can make an informed decision. 13% on its own just doesn't convey enough information to make that judgement which is why I commented on it.