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We read the study by Zöllner and colleagues published recently in Thorax about the levelling off of asthma and allergies among children in Germany between 1992 and 2001.1 We have published a study looking at the same issue and using a similar protocol (ISAAC)2 to assess the symptoms, diagnosis, and severity of asthma and allergies in more than 15 000 children aged 6–7 and 13–14 years between 1995 and 2000 in Münster, Germany.3 We found a tendency towards an increase in current symptoms of asthma and allergies in both age groups, but more so among girls.3
Indices of diagnosis either remained the same or increased in parallel with the increase in symptoms, arguing against a change in diagnostic behaviour as an explanation for our results. Indices of severity also showed a homogenous increase in the 5 year study period, pointing towards an increase in the overall burden of asthma and allergies within the society.3
Regrettably, these results, coming from Germany, were not considered in either the discussion of Zöllner’s report or in the affirmative title that no increase in asthma and allergies occurred in Germany in the 1990s. Even more regrettable is the fact that when our study was alluded to in the discussion and conclusion of the paper by Zöllner et al, it was cited—contrary to our results—as one of the studies showing a decrease or levelling off of asthma and allergies among children.1
Unfortunately, the paper by Maziak et al1 published in Allergy was listed as reference number 18 instead of number 21 in the reference list of our paper.2 We apologise for any misunderstanding which may have arisen from this error. A correction is published below.
In the paper by Maziak et al1 the prevalences in 1994/5 and 1999/2000 are compared. As we know from our own studies, trend analyses based on (only) two time points may be difficult and should be interpreted with caution. Indeed, in their investigation Maziak et al did not find a significant increase in the lifetime prevalence of asthma and hay fever, except in one subgroup. The effect found in 13–14 year old girls could also be due to a former underdiagnosis of asthma in girls, as discussed in their paper.
Since our results are based on six cross sectional surveys, we consider the title and the conclusion—that we did not see an increase in asthma and allergies from 1992 to 2001—to be appropriate.