Researchers from Vanderbilt University analysed data from 95,000 children in Tennessee born between 1995 and 2000 and followed through to 2005. They found that the winter virus peak immediately following birth predicted asthma development, independently of other factors.

Birth at that time was associated with a 30 per cent increased risk of developing asthma.

'We have shown that there is variation in the risk of developing asthma by the timing of birth in relation to the winter peak for each year studied,' the researchers say.

'This supports a causal relationship of childhood asthma with the winter virus peak after birth.'

tom.moberly@haymarket.com

• Am J Respir Crit Care Med 2008: 178; 1,123-29

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