Allergies and asthma are a continuing health problem in most developed countries, but just how do these ailments develop over the course of a childhood? In a population-based study designed to help answer this question, researchers at the Norwegian University of Science and Technology (NTNU) found that 40 per cent -- or two of five -- of nearly 5,000 two-year-olds had at least one reported allergy-related disorder.
The most common symptom was wheezing, which was reported in 26 per cent of all children in the study, says Ingeborg Smidesang, a PhD candidate in the university's Faculty of Medicine, and the primary author of the study.
Researchers are careful to point out that there is no guarantee that children who wheeze at two years old will grow up with asthma. "One of the challenges here is that we don't know which wheezers will develop asthma," Smidesang says.
The findings are among the first to illustrate the scope of allergy-related problems in such a young group of children, and the challenges that these problems pose for both families and for public health systems overall. "If you think about something like moderate atopic eczema, which can involve quite a few doctor's visits, and a lot of work on the part of parents, it is quite a big deal," she says. "This can be quite a burden."
The study has been published in an online version of Pediatric Allergy and Immunology, a peer-reviewed academic journal. Among the findings reported is that fully 21 per cent of the 5000 children in the study, or about 1000 children, had been tested for allergies. Roughly 60 per cent of these 1000 children were reported by their parents to have had a positive allergy test. However, when researchers randomly selected 390 children for allergy testing, only eight per cent had a positive test. The allergy-related disorders that were studied were eczema, asthma, asthma-like symptoms and hay fever. Researchers found that boys were more likely than girls to have an allergy-related disorder, Smidesang said.
Allergy-related disorders vary widely within countries and between countries. For example, children in northern Norway are more likely than children in southern Norway to have atopic dermatitis, Smidesang said, probably because the winters are longer in the north than in the south. Another comparison between Sweden and the UK in 2002-2003 showed that asthma symptoms in children were roughly 10 per cent in Sweden compared to 21 per cent in the UK. Researchers can make conjectures about what causes these variations, but the bottom line is that medical researchers really don't understand what causes children to develop allergies and what can be done to prevent them.
Smidesang's study is a part of a larger effort called PACT (Prevention of Allergy among Children in Trondheim), which began in 2000 to try to better understand how allergy-related symptoms develop in children and to investigate the effectiveness of risk-factor intervention, including increasing omega-3 fatty acid intake, reducing parental smoking and indoor dampness. A control group of 14 000 children, from which the current study is drawn, was established to track fluctuations in risk factor levels and to provide comparison data. A second group of roughly 3000 children was recruited for a proactive intervention effort. The programme started during pregnancy and continued until the children reached the age of 2. The 390 children who were randomly selected for skin prick allergy testing will be followed up when they are 6 years old.
The above story is based on materials provided by The Norwegian University of Science and Technology (NTNU). Note: Materials may be edited for content and length.
- Ingeborg Smidesang, Marit Saunes, Ola Storrø, Torbjørn Øien, Turid Lingaas Holmen, Roar Johnsen and Anne Hildur Henriksen. Allergy related disorders among 2-yrs olds in a general population. The PACT Study Allergy related disorders in 2-yrs olds. Pediatric Allergy and Immunology, 2009; DOI: 10.1111/j.1399-3038.2009.00954.x
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