2.4. Trends in the occurrence of atopic disorders

There is a world-wide variation in the prevalence of atopic disorders. High prevalence rates seem to be present in Australia and Western Europe and low rates in Asia and Eastern Europe (Remes 1998, Harju 1999, Dunder et al. 2001). Further, evidence has been accumulating to indicate that the prevalence of atopic disorders has been increasing in recent decades in Western countries, including Finland (Harju et al. 1998, Konsensuslausuma 1998, Remes 1998, Galil 2000, Pekkanen et al. 2001a, Savolainen 2001, Vartiainen et al. 2002). Earlier, because only few of the studies investigating the presence of atopic disorders used objective measurements in repeated surveys, there was a critical debate about whether the observed increased rates were true or biased due to many possible confounders (Magnus & Jaakkola 1997, Remes 1998). At present, there is a consensus about the upward trend in the occurrence of atopic disorders (Konsensuslausuma 1998, Pekkanen et al. 2001a, Savolainen 2001, Hannuksela 2002). In Finland, it has been suggested that 15%–20%, 2%–6% and 2%–5% of adult people are nowadays suffering from allergic rhinitis, asthma and atopic dermatitis, respectively. The corresponding figures for children are 20%–25%, 5%–7% and 15%–19%, respectively (Haahtela et al. 1999b). Thus, it has been estimated that nowadays about one million Finnish people are suffering from asthma, allergic rhinitis or atopic dermatitis (Savolainen 2001).