Women who are overweight as young children more than triple their risk of developing adult on-set asthma, a new University of Melbourne study has found.

The study, published in the current edition of the European Respiratory Journal, is the first to show a link between childhood obesity and adult onset asthma in women.

Researcher John Burgess, from the School of Population Health, said the study used data from almost 1500 people who took part in the Tasmanian Asthma Study as seven-year-olds in 1968 and as 32-year-olds in 1992.

The data allowed investigators to check for a possible link between the children’s body mass index (BMI) at seven years and what happened to their lungs 25 years later.

The results showed that girls who did not have asthma at the age of seven, but were in the top 25 per cent for BMI, were over three times more likely to develop asthma as adults, when compared to similar girls in the lowest 25 per cent of BMI.

The increased risk remained the same after taking into account other factors such as childhood allergies, the degree of lung development at the age of seven and smoking later in life.

The same risk did not apply to overweight boys.

Dr Burgess said that although previous studies had shown a link between obesity and adult asthma in women, this was the first study to show how excess weight in children might affect their lung health as adults.

“This study shows that the known increased risk of asthma in obese women could have actually started when they were children,’’ Dr Burgess said.

“It adds to a growing body of evidence detailing the harmful long-term effects of excess weight in childhood.

“In particular, health messages should highlight the importance of young girls maintaining a healthy body weight to prevent asthma later in life.’’

Dr Burgess said as childhood obesity data from this study were taken in 1968, there would now be many more children at risk of developing adult on-set asthma.

“There prevalence and extent of obesity among young girls has grown significantly since 1968,’’ he said.

“This means that there are now many more young girls who are overweight and could be a high risk of developing asthma in future.’’

Dr Burgess said it was not known why only obese girls were at increased risk of adult onset asthma.

“Female hormones are known to affect the lungs and these may start acting at a younger age in obese girls, who often reach puberty earlier than normal weight girls,’’ he said. “However, our current study does not support or rule out this theory and further research will be needed to determine if this is the case.’’