Autumn babies may be more likely to get asthma as they grow older, new research suggests.
Children with autumn birthdays will be about 4 months old during their first winter. Researchers think that children of this age are more vulnerable to chest infections, which could play a part in causing asthma.
What do we know already?
Up to 1 in 10 children in the UK have asthma. Children are more at risk of getting asthma if they're from a family with a history of allergies, such as hay fever or eczema. And children whose parents smoke are also more likely to get asthma.
Some doctors think that getting chest infections may also play a part in causing asthma. But it's difficult to test this idea. It might just be that some children have weak lungs, and are vulnerable to both infections and asthma.
People tend to get coughs and chest infections more often in winter. So, researchers in the US came up with an interesting idea. They looked at when children were born in relation to winter. If infections really cause asthma, children who were at a vulnerable age during their first winter would be more likely to get chest infections, and more likely to get asthma. If there was no link, children would have the same risk of asthma no matter what time of year they were born.
What does the new study say?
Researchers looked at more than 95,000 children over several years. The peak time for chest infections fell between December and February each year. Children who were around 4 months old at this time had a slightly higher risk of getting a common chest infection called bronchiolitis, and of going on to get asthma. This suggests that chest infections could be a cause of asthma for some children.
Four months is likely to be the time that babies are most vulnerable to infections. At this age, babies have lost the immune system boost they get from their mothers, but they're not old enough to have fully built up their own immunity.
How reliable are the findings?
Although this study suggests that chest infections have some effect on a child's risk of asthma, it's not absolute proof. It could be that colder weather affects children's lungs in some way, and raises the risk of asthma for autumn babies.
Where does the study come from?
The study was done by looking at medical records for children in Tennessee. It was published in the American Journal of Respiratory and Critical Care Medicine, which is owned by the American Thoracic Society.
What does this mean for me?
According to the new study, chest infections can play a part in causing asthma. However, the researchers don't think that all children are equally at risk. Some children might be more vulnerable to asthma because of their genes, allowing an infection to trigger the disease. Other children might get chest infections without going on to get asthma. So it's hard to say what the risks are for your child.
What should I do now?
It's difficult, if not impossible, to protect a child from viral infections, including chest infections: the researchers say that about 7 in 10 children have had bronchiolitis by the age of 12 months. Bronchiolitis doesn't always need treatment, and for many children the infection will be mild. Only 2 in 10 children in the study needed medical attention for a chest infection by 12 months of age.
Trying to avoid infections could even have unintended consequences. Keeping your child at home might protect them from other children's germs, but some studies show that going to nursery makes children less likely to get asthma.
You might be able to cut your child's risk of asthma by not smoking while pregnant, and by not smoking around your children while they're young.
Even if your child does get asthma, treatments work well. And up to three-quarters of children with asthma grow out of it.
From:
Wu P, Dupont WD, Griffin MR, at al. Evidence of a causal role of winter virus infection during infancy in early childhood asthma. American Journal of Respiratory and Critical Care Medicine. 2008;178:1123-1129.
To read more, see our information about asthma in children.
