Asthma prevalence may be in decline

The rise in prevalence of asthma symptoms in English-speaking countries such as the United Kingdom and New Zealand has peaked and may even be in decline, researchers have found.

Professor Neil Pearce of the Centre for Public Health Research is the lead author of a paper from phase three of the International Study of Asthma and Allergies in Childhood (ISAAC) published in the international medical journal Thorax this month. Key findings include that in most high asthma prevalence countries, particularly English-speaking countries, fewer people are reporting asthma symptoms. Countries in other parts of the world are showing a marked increase in reporting of asthma symptoms, including Latin American countries such as Costa Rica, Panama, Chile, Mexico and Argentina.

The phase one findings, published in 1998 showed that the highest prevalence of symptoms in a 12-month period were reported in English-speaking countries such as Britain, Australia, the United States, Canada, New Zealand and Ireland. By phase three, the prevalence of asthma symptoms in 13-14 year old children in these countries had dropped by from 30 per cent to 25 per cent.

Phase one found relatively low prevalence in Africa and Asia, with the exception of affluent countries such as Japan and Singapore. "The phase three findings indicate that the striking increases for Latin American countries may lead to a future where asthma is described as a Spanish and Portuguese speaking disease, rather than as an English-speaking disease as it has been known in the past," says Professor Pearce.

"The modest increases for some Asian countries are of potentially major significance given the size of Asia's population and rapid economic growth. Thus, although asthma symptom prevalence is no longer increasing in English language and Western European countries, its global burden may continue to rise."

The ISAAC study is the most extensive international survey of asthma symptom prevalence ever performed. It is led by Professor Innes Asher, at Auckland University's Department of Paediatrics, and Professor Pearce is a member of the five-person executive committee. Professors Asher, Pearce and others founded the study in 1990. More than two million children in 100 countries have been studied. Phase one research was undertaken in the early 1990s, with the phase three surveys taking place five to 10 years later.

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