New study links gender to childhood condition

When boys hit puberty, new research suggests they are much more likely to grow out of childhood asthma then girls.

According to Dr Kelan Tantisira, who led the study at Harvard Medical School, this is the first time that the gender differences in asthma have been investigated in this way.

Over 1,000 asthmatic children were given standard 'methacholine challenge' tests over a period of nearly nine years. Methacholine is used by doctors to diagnose bronchial hyperreactivity by causing airway narrowing, and the substance was administered under clinical conditions with researchers noting the dosage required to provoke the reaction.

Over time, girls mostly required the same dosage but the amount needed to provoke the same reaction in boys increased.

When the study began, the children were aged between five and 12. By the time they reached 18, only 14% of girls did not react to the methacholine, compared with 27% of boys.

In the UK, one child in 10 has childhood asthma but doesn't go on to be an adult asthmatic. The reasons behind this are not understood but it looks likely that sex hormones might play a role.

Dr Tantisira said 'Especially intriguing is that the differences in gender begin at the time of transition into early puberty.'

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