Triple asthma whammy for big girls

Overweight girls have triple the risk of developing asthma as adults, and Australian specialists believe female sex hormones might be at fault.

In a world first, University of Melbourne researchers have found a link between childhood obesity and adult-onset asthma in women.

The study of 1,500 people analysed the body mass index (BMI) of girls when they were seven years old and measured it against their lung function 25 years later.

The results showed that non-asthmatic girls in the top 25 per cent for BMI were over three times more likely to develop the respiratory condition later when compared to similar girls in the lowest 25 BMI range.

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.

Previous research has linked genetics, weight, exposure to allergies and other environmental factors to asthma risk.

This study published Wednesday in the European Respiratory Journal is the first to shed more light on the obesity link.

"It shows that the known increased risk of asthma in obese women could have actually started when they were children," said researcher John Burgess, from the school of population health.

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

Dr Burgess said as childhood obesity data from this study was taken almost 40 years ago, there would now be many more children at risk of developing adult on-set asthma.

"The 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."

The same disease link was not found in boys, making the researchers suspicious that female-specific hormones could be to blame for the connection.

Estrogen is essential for normal female sexual development, but the hormone is also known to affect the immune system and the lungs.

"Heavier girls tend to reach puberty earlier than girls of normal weight," Dr Burgess said.

"It's postulated then that the effects of exposure to estrogens at a younger age possibly `programs' the lungs to develop asthma later on, but that purely a hypothesis at this stage."