A study showing more than one quarter of asthmatics have symptoms of dysfunctional breathing might explain the anecdotal success of the Buteyko method in treating asthma, researchers say.

The UK study found many people diagnosed with asthma might benefit from breathing retraining.

Researchers asked 219 patients with asthma to complete a questionnaire assessing 16 symptoms associated with abnormal breathing, such as fast or deep breathing, shortness of breath, tingling in fingers and hands, and anxiety.

One-third of women and one-fifth of men had a complex of abnormal breathing symptoms suggestive of hyperventilation syndrome or dysfunctional breathing, according to the findings in the BMJ (5 May).

"There may be an important unrecognised diagnostic overlap between asthma and dysfunctional breathing," the researchers wrote.

The study found many patients might be experiencing avoidable morbidity because of inappropriate diagnosis and ineffective treatment. And it suggested the findings might explain the reported success of the Buteyko method, which claims to treat asthma by retraining the breathing pattern to correct hyperventilation.

Associate Professor John Wilson, director of the Australian National Asthma Campaign, said it was difficult to screen patients for dysfunctional breathing and it may be misdiagnosed as asthma. Professor Wilson, from the department of respiratory medicine at Alfred Hospital in Melbourne, said asthma should not be diagnosed by history and physical examination alone.

The best diagnostic tools were objective assessments of airflow, such as spirometry or peak expiratory flow rate, where there was a change of at least 15% in PEFR before and after exercise.

However, there was likely to be significant crossover between asthma and dysfunctional breathing.

Breathing training, which was available through pulmonary rehabilitation clinics, could often help patients understand and cope better with the symptoms of both conditions, he said.