Obesity and excess weight in childhood may increase asthma risk, study finds

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Long-term study of 5,000 children suggests likelihood of developing condition rises 55% for every extra unit of BMI

A child being treated for asthma.
A child being treated for asthma. Public health experts say research suggesting a link between obesity and asthma reinforces the importance of developing health lifestyles from an early age. Photograph: Voisin/Phanie/Rex Features

Excess weight and obesity in children may be fuelling the asthma epidemic facing many countries, a joint study from Australian and UK researchers has found, prompting peak asthma groups to re-emphasise the importance of a healthy lifestyle in childhood.

The risk of developing the condition, which causes chronic inflammation of the airways, increases by 55% for every extra unit of body mass index (BMI), University of Bristol and University of Queensland researchers found.

The study looked at almost 5,000 children with asthma by the age of seven and a half who were enrolled in a long-term study of parents and children in the UK.

Researchers gave children a score based on 32 independent body mass-related DNA sequence variations, and associations with body mass, fat mass, lean mass, and asthma were then estimated.

Lead author of the study and allergy expert Dr Raquel Granell said many studies had explored the influence of environmental factors such as pollen and fumes on asthma in childhood.

But while the link between BMI and asthma has long been suspected, until now no causal link had been shown, she said.

“Higher BMI in mid-childhood could help explain some of the increase in asthma risk toward the end of the 20th century,” she said, “although the continued rise in obesity but with a slowing in the rise in asthma prevalence in some countries implies that other non-BMI-related factors are also likely to be important.”

More research was needed to confirm a causal link between BMI and asthma, she said.

The Australian Institute of Health and Welfare reports that Australia, the UK, New Zealand and Ireland have among the highest prevalence of asthma in children. More than two million Australians have the condition.

While the prevalence of asthma has fallen in children and young adults in Australia, it is high by international standards.

Respiratory physician and the chair of Asthma Australia’s medical and scientific committee, Dr Simon Bowler, said the new research had helped to define the relationship between asthma and childhood obesity.

“Whilst it has been widely acknowledged that levels of stored body fat impact on health and wellness of people and those with asthma in particular, this new research highlights obesity as a marker of asthma in children,” he said.

“A cure for asthma is a long way off but people with asthma can manage the disease with medications and preventative health approaches including manage their or their children’s weight.”

Up to one out of every nine children have asthma in Australia, he said, making managing a child’s weight in early childhood years important for parents.

Dr Samantha Walker, the director of research and policy at Asthma UK, said the research, published in PLOS Medicine, a peer-reviewed medical journal, was in line with other studies linking obesity with asthma. Asthma was a complex condition particularly in children, she said.

“Keeping your BMI within normal limits brings all sorts of health benefits and may help reduce the risk of children developing asthma.”