In a world first, researchers have come up with a figure on how many cases of paediatric asthma are directly attributable to obesity.

In the study published in Pediatrics, the research team from several states in the US reviewed asthma incidence rates from more than half a million children, half of whom were overweight or obese and half of whom were a healthy weight.

They discovered that regardless of the diagnostic definition used, about a quarter of new asthma cases in children with obesity were directly attributable to obesity.

And 10 percent of all cases would be avoided if children were not overweight or obese.

Currently there are few known preventable risk factors that can be used to reduce childhood asthma, the study authors noted.

“With these data, it is suggested that reducing the onset of obesity in childhood would significantly reduce the public health burden of asthma in children,” they wrote.

As previous research had shown that obesity among children with asthma increases disease severity their finding were “particularly compelling,” they added.