Risk of severe asthma episodes predicted from fluctuation analysis of airway function

A startling new study published in the science journal Nature this week (Nature Vol 438, issue 7068, pp 667-670) reveals that inhalers used by asthmatics for symptomatic relief of their condition might actually increase the likelihood of an acute attack.

The study by an international team of researchers, including Professor Mike Silverman of the University of Leicester, uses mathematical modelling techniques to try and 'predict' when an asthma attack might occur in an individual.

Professor Silverman, Professor of Child Health in the Department of Infection, Immunity & Inflammation at the University of Leicester, said:

"Asthma is a very common and often disabling condition. About 1 in 10 children and 1 in 20 adults suffer from the disease. Although it is a chronic illness, variability in both the severity and interval between attacks, is one of its most characteristic features. Attacks appear to be "random", as a result of a whole range of external agents, such as common colds, fluctuations in the weather, and exposure to allergic triggers.

"Our new study applies mathematical models which are commonly used in engineering, but not in medicine to study the occurrence of asthma attacks. The mathematical models are based on processes which are commonly known as "chaos". Strangely, chaos as applied to complex systems, such as the human body, engineering systems, and of course the weather, is not random but dependent on the interaction of many individual components. It is just unpredictable.

"We have analysed lung function measurements, taken daily for six months in a large group of asthma sufferers, during a clinical trial which had been carried out in New Zealand. The apparently random nature of these lung function measurements conceals a hidden order, referred to as "long-term correlation".

"We showed that the degree of ordering improves as the clinical condition improves. It is possible to analyse the data for individual subjects, and to predict the likelihood of an acute attack occurring over the next month. Alarmingly, the results show that an inhaler which is commonly used by asthmatics for relief, if used regularly, can increase the instability of lung function, and increase the likelihood of an acute attack ."

Professor Silverman said that the implications of this analysis are considerable:

"It may be possible to determine the risk of a severe attack of asthma in individual subjects, and to use the information to modify their treatment. It may also be possible to carry out clinical trials of new anti-asthma treatments in a much more efficient way than has been done in the past. "

He said previously, in order to determine the impact of a new asthma treatment on severe attacks, long periods of observation were necessary, in order to accumulate sufficient attacks of asthma to be certain that the new drug was better than previous forms of therapy.

"Using the mathematical modelling techniques described in the Nature paper, it will be possible to obtain information about the instability of asthma from a short period of observation, without waiting for an acute attack to develop. This will save both time and money, and allow new drugs to be introduced into clinical practice sooner than hitherto."