Changing Prevalence and Severity of Childhood Allergic Diseases in Kyoto, Japan, from 1996 to 2006

BACKGROUND: Published data regarding changes in the prevalence of childhood allergic diseases in Japan have been limited. METHODS: To observe changes in the recent trends of the childhood allergy epidemic in Japan, a population-based questionnaire survey of allergic diseases was conducted among 13,215 schoolchildren, aged 7 to 15 years, in Kyoto, Japan in 2006. The results were compared with those obtained in the 1996 survey using the same scale and methods in the same region. RESULTS: The prevalences of bronchial asthma (BA), atopic dermatitis (AD), allergic rhinitis (AR), and allergic conjunctivitis (AC) in 1996 and 2006 were 5.1% and 5.0% (p = 0.58), 4.2% and 5.6% (p < 0.0001), 20.3% and 27.4% (p < 0.0001), and 13.3% and 25.2% (p < 0.0001), respectively. Although the distribution of BA severity improved, the severity distribution of AD, AR, and AC all deteriorated. The lifetime prevalence (present prevalence and past history combined) of BA increased from 6.5% to 7.6% (p < 0.0001). The sex ratio analysis showed that the female predominance in the prevalence of AD observed in 1996 disappeared in 2006, indicating a particular rise in AD prevalence among boys. CONCLUSIONS: Overall, the results indicate that the rising trend of allergic diseases, especially in AD, AR, and AC, continues among schoolchildren living in Kyoto, Japan. Special attention should be paid to skin and nasoocular symptoms.