Abstract
BackgroundThere are few studies on age and sex-specific asthma prevalence in the age range 1–6 years. The purpose of this report was to estimate age and sex specific asthma prevalence in preschool children and to analyse the influence of possible demographic and geographic determinants.MethodsAll 70 allergen avoidance day-care centres and 140 matched ordinary day-care centres across Sweden were sampled. The parents of all 8,757 children attending these day-care centres received the International Study of Asthma and Allergies in Childhood (ISAAC) written questionnaire, supplemented with questions on medical treatment, physician assessed asthma diagnosis, and other asthma related questions. The response rate was 68%.ResultsThe age specific asthma prevalence, adjusted for the underlying municipality population size, was among boys 9.7% at age 1, 11.1% at age 2, 11.4 at age 3, 10.5 at age 4, 8.7 at age 5, and 6.4 at age 6. The corresponding proportions among girls were 8.9%, 9.9%, 9.8%, 8.8%, 7.0%, and 5.0%, on average 9.6% for boys and 8.2% for girls, altogether 8.9%. In addition to age and sex the prevalence increased by municipality population density, a proxy for degree of urbanisation. Moreover, there was a remaining weak geographical gradient with increasing prevalence towards the north and the west.ConclusionThe age-specific asthma prevalence was curvilinear with a peak around age 3 and somewhat higher for boys than for girls. The asthma prevalence increased in a slowly accelerating pace by municipality population density as a proxy for degree of urbanisation.
Highlights
There are few studies on age and sex-specific asthma prevalence in the age range 1–6 years
BMC Public Health 2009, 9:303 http://www.biomedcentral.com/1471-2458/9/303 in Childhood (ISAAC), the prevalence of wheezing during the last year among 6–7 year old children in Sweden is in the middle of the international range [3,4,5]
Characteristics of the study population The proportion of children was similar in the age range 2– 5 years and lower for those 1 and 6 years old, Table 1
Summary
There are few studies on age and sex-specific asthma prevalence in the age range 1–6 years. The purpose of this report was to estimate age and sex specific asthma prevalence in preschool children and to analyse the influence of possible demographic and geographic determinants. We found only one study on possible gradients within countries showing an increasing prevalence towards the north among Swedish school children [13]. It is doubtful what geographical gradients stand for. As far as we know there are no studies on how much of the influence of geographical location on asthma prevalence that can be explained by degree of urbanisation
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