Asthma falls in English-speaking world, up in Latin America: report

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An asthma epidemic in English-speaking countries around the world appears to be declining but the disease is becoming much more common in Latin America, according to research reported on Saturday.

Scientists who have studied asthma in an international survey of two million children in 100 countries since 1990 are baffled by the trends, Wellington's Dominion Post reported.

"All we know at this stage is that something big is going on globally," Neil Pearce, a professor at Massey University's Centre for Public Health Research, told the paper, dubbing it a dramatic turnaround.

Pearce was a founding member of the International Study of Asthma and Allergies in Childhood and is lead author of a paper on the survey published in the international medical journal Thorax this month.

"When we started this research in the 1990s, the highest prevalence of symptoms were in English-speaking countries - Britain, Australia, the United States, Canada, New Zealand and Ireland," he said.

"By phase three, the prevalence of asthma symptoms in 13- and 14-year-old children in these countries had dropped from 30 per cent to 25 per cent."

Pearce said that meanwhile, other parts of the world were showing a marked increase in reporting asthma symptoms, including Latin American countries Brazil, Chile, Costa Rica, Panama, Chile, Mexico and Argentina.

In future, asthma could be described as "a Spanish and Portuguese-speaking disease," Pearce said.

Despite the extensive survey, researchers still had no idea what made asthma rates increase or why they have started to fall in some places, he said.

Fifteen years ago, the dominant theory blamed dust mites and other allergens for asthma symptoms, but Pearce said that was superseded by the "hygiene hypothesis," which suggested over-use of detergents altered children's immune systems, making them more susceptible to the disease.

He said that theory followed global trends to some degree but did not explain them completely, as asthma was rising in Brazil and Chile, although their infection rates were also high. dpa db cc