Up to one in five British school children suffers from asthma-like symptoms, according to a Leicester University survey.
Researchers following 1,500 children from birth found that asthma is still a major problem despite a report earlier this week from a Royal College of General Practitioners monitoring unit suggesting the number of acute asthma attacks may be on the decline.
The Leicester research reveals two sorts of asthma, one affecting pre-school children, the second manifesting itself later at school age.
Twenty per cent of the 1,422 eight to 13-year-olds questioned by researchers from the department of child health reported wheezing in the past 12 months; 11 per cent were being prescribed steroid inhalers.
Though the first figure is lower than the 30 per cent reported earlier this year in a national survey when teenagers, rather than their parents, were questioned, it contrasts with the 3 to 5 per cent of teens reporting such symptoms 20 years ago. The rise could be linked to exposure to different pollutants, such as those from traffic, or to changes in diet, or possibly indoor environment.
The cohort was first surveyed in 1990 when the children were aged up to five. Then, 12 per cent reported wheezing in the preceding year. Eight years on, just under half of those children were still wheezing. But many children who had not wheezed were now reporting asthma symptoms.
Mike Silverman, who is leading the study, said: "The mystery is why it takes several years for some children to develop asthma. What has changed by the time the child reaches ten-years-old? Why do so many more have it aged eight to 13 than 0 to five, and why are they different children?" He suggested that there may be two different diseases. "Both are asthma in the sense that both involve airway obstruction from time to time. They may look very similar - but the actual diseases may well be different."
Professor Silverman added that asthma in the under-fives does not seem to be triggered by an allergic reaction as in the school-age asthma, but rather by a virus infection such as the common cold.