Obese people incorrectly diagnosed with asthma

May 18 2005

Clinical tests carried out by the Woolcock Institute of Medical Research indicate obese people may be incorrectly being diagnosed and treated for asthma when in fact the reason for shortness of breath may be related to the extra weight they carry.

The recent study of nearly 300 people in NSW aged between 28 to 30 years, found that after allowing for the presence of asthma and for cigarette smoking, airways were narrower in obese subjects due to compression of the lungs from the extra weight.

In addition there was even further narrowing of airways with increasing obesity that could not be explained by lung compression alone.

Dr Greg King, Head of Imaging Group, Woolcock Institute of Medical Research, said the findings suggest there are structural or functional changes in the airways specifically associated with increasing body mass index (BMI).

"This is the first time the role of body mass index (BMI) in determining airway calibre has been reported," he said, "with our study indicating a stronger relationship present in males."

"This airway narrowing and subsequent reduction in lung volume may cause shortness of breath and wheeze in obese subjects without them having asthma."

Dr King suggests the incorrect diagnosis of asthma in obese people could lead to unnecessary treatment when the most appropriate and effective treatment would actually be weight loss.

"In addition, obese people who experience symptoms similar to asthma may be discouraged from exercise which is the last thing you want," he said.

With both obesity and asthma becoming increasing problems in western societies, it is important to understand and make correct diagnoses so the best treatment can be applied.

"The Woolcock Institute hopes to undertake further studies to fully understand the cause of this increasing airway narrowing with increasing obesity."

Dr King's paper " Effect of Bodyweight on Airway Calibre" is in the May issue of the European Respiratory Journal.

http://www.woolcock.org.au/