According to researchers asthma rates among four-to five-year-olds fell by almost a quarter for every 343 extra trees per square kilometre in an urban area.
Asthma has increased by around 160 per cent globally in the last two decades, although scientists are not sure what is causing this rise. Some have suggested that excessive cleanliness in the home is the cause, while another theory blames the increasing use of antibiotics.
The new analysis by researchers who studied data on asthma rates across New York suggests that a leafy suburban lifestyle goes some way to protecting children against the disease.
''Street trees were associated with a lower prevalence of early childhood asthmas,'' the team wrote in the Journal of Epidemiology and Community Health.
Professor Irwin McLean, who studies asthma at the University of Dundee, said it was a ''very interesting study'' but he urged caution in interpreting the results. ''It shows that there is some correlation between suburban living and [a reduction in asthma].
That doesn't mean you should go out and plant a load of trees around your house if you want to stop your kids from getting asthma,'' he said.
McLean added: "It is very difficult in environmental studies to dissect out one single triggering factor. There won't be a motorway running through a tree-lined suburb, for example, with all the pollution associated with that. The obvious thing people are going to think is, if I plant a load of trees around me that will protect me from asthma.
''That may not be the case. If you were living by the side of a motorway and you planted a forest around you, you are still going to get asthma-if the motorway is the cause of the asthma,'' he said.
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