28 August 2006

Allergies increase globally

The number of children with allergies and asthma is increasing worldwide, especially among the youngest, researchers report.

The number of children with allergies and asthma is increasing worldwide, especially among the youngest, researchers report.

In 1991, the International Study of Asthma and Allergies in Childhood looked at the global prevalence of asthma, hay fever and eczema. Between 2002 and 2003, Dr Innes Asher of the University of Auckland, New Zealand, and colleagues repeated the survey to see if there were any changes.

In its study, Asher's team questioned the parents of more than 193 000 children aged six to seven years from 37 countries. They asked about the presence of symptoms of asthma and allergies, such as wheezing, in their child. The researchers also surveyed some 304 680 children, aged 13 to 14 years from 56 countries, asking the same questions. Countries included Brazil, Canada, Great Britain, Iran, New Zealand, South Africa and Sweden.

The researchers found that increases in allergies were more common than decreases and occurred more often in the younger age group. The greatest increases were for eczema in the younger group and for hay fever in both age groups.

'Data has direct relevance'
However, among the older children, in whom cases of asthma had previously been high, there was a decrease in symptoms. Only in Asia-Pacific nations and India did increases in the prevalence of all three disorders happen more often in both age groups.

"The data has direct relevance for health service delivery in the countries included in the study as well as providing a basis for understanding these disorders," the authors wrote." In almost all centers, there was a change in prevalence of one or more disorders over time. Although changes in mean annual prevalence to the order of 0.5% might sound small, such changes could have substantial public health implications, especially since the increases took place most commonly in heavily populated countries," they concluded.

The study findings were published in the August 26 issue of The Lancet. One expert thinks the increase in allergies needs to be studied to find the causes and cures.

"Allergies are an important cause of seasonal miseries for millions of people," said Dr David L. Katz, an associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine. "And they can be the precipitant of serious and even life-threatening conditions, from asthma to anaphylaxis."

'Why is this happening?'
"The obvious question is: Why is this happening?" Katz added. "The possibilities encompass environmental contaminants and pollution; changes in the food supply; changes in exposures to infectious disease; and other influences that might alter immune system function."

Another study in the same journal issue found that children who develop wheezing from allergens, such as cat hair, during the first three years of life are likely to go on to develop asthma.

In the study, Dr. Sabina Illi, of the University Children's Hospital, Munich, Germany, and colleagues studied the prevalence of allergen exposure in more than 1 300 children. Among these children, 500 had risk factors for allergen sensitivity at birth.

The researchers found that 90% of the children who experienced wheezing but weren't at risk for allergies lost their symptoms at school age and had normal lung function at puberty.

But, the children who had repeated wheezing and sensitivity to allergens in the first three years of life were more likely to develop a loss of lung function and asthma. High levels of exposure to allergens also contributed to development of asthma, the researchers added.

The term 'asthma' outdated
"Given the good prognosis for non-atopic [non-allergy susceptible] wheezing children, the need for these individuals to continue to take inhaled corticosteroids on a regular basis should be re-assessed," the researchers said. In addition, an editorial in the journal calls for abolishing the term asthma.

"Asthma is unlikely to be a single disease, so we should abolish the term altogether," the editorial stated. Asthma includes different symptoms, such as wheezing, coughing, and difficulty breathing. It is caused by inflammation of the airways. But what triggers this inflammation and why some people develop asthma and others do not isn't known, according to the editorial.

The editorial also concluded that asthma sufferers can have different triggers, symptoms, and responses to treatment. There is an emerging consensus that asthma is not a single disease.

Dr Jonathan Field is director of the allergy and asthma clinic at NYU Medical Center/Bellevue, in New York City. He said there are "many theories" to explain the rise in pediatric allergies.

"In part, this is a byproduct of improving quality of life," he said. "Better vaccines, sanitation and public health are a blessing, but the downside is the impact they have on the immune system. For example, before the unification of Germany, East Germany had lower asthma rates. Now, the former East Germany has caught up. This is a global phenomenon, and it will be one of the largest health-care issues facing us in the future."

Read more:
Visit our Asthma Centre
Allergies - it's war


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