[Epidemiology of @entity1576 in XXXX ].

@entity1 @entity3617 @entity2023 @entity1353 @entity565 @entity402 @entity5924 @entity1576
Epidemiology of paediatric @entity1576 allows the approach to causal and preventive risk factors by studying groups or sub groups of @entity1 in different locations and under different conditions. This is, however, complicated by the lack of consensus on disease definitions, which renders comparisons between studies difficult. Atopy is usually defined by the presence of positive skin tests (wheal size of at least a mean diameter > or = 3 mm), by the presence of specific IgE, or by the presence of increased total IgE (> or = 100 UI/mL). @entity565 is not well defined, complicated by the high prevalence of @entity5924 ; one thus questions between wheezing or wheezy @entity3617 . Prevalence is high: among early wheezers, two populations will be defined by the medium term evolution: transient wheezers and persistent wheezers. Risk factors for these two conditions are different. @entity565 may be defined by the diagnosis of @entity565 (specific but fairly non-sensitive), by asthmatic symptoms (wheezing, waking by an attack of @entity1353 ) (sensitive but not very specific), or by the combination of symptoms and airway hyperresponsiveness. The ISAAC study has standardised a questionnaire to assess the prevalence of @entity565 . The preliminary results show that there are wide variations across the world. The prevalence is low in Africa and Asia, intermediate in Europe, and high in Anglo-Saxon countries. The prevalence of @entity565 has gradually increased over the past 20 years in developed countries. @entity565 and @entity402 are closely associated in @entity1 . Risk factors are genetic, associated with sex and environmental factors. Among these, allergic sensitisation is associated with the degree of exposure to allergens. Westernization of way of life is associated with increased prevalence of @entity402 , @entity2023 and @entity565 . Atopy seems inversely correlated to certain infections. Passive smoking is clearly associated with early wheezing. This and atmospheric pollution aggravate childhood @entity565 . However, the inducing role of pollution on @entity565 is still controversial.
