The Relationship between Pollen Count Levels and Prevalence of Japanese Cedar Pollinosis in Northeast Japan

Background: The prevalence of Japanese cedar (JC) pollinosis in Japanese children is increasing. However, few studies have reported the relationship between pollen count levels and the prevalence of pollinosis. To evaluate the relationship between JC pollen count levels and the prevalence of pollinosis in children, we investigated the sensitization and development of symptoms for JC pollen in two areas of Akita in northeast Japan with contrasting levels of exposure to JC pollen. Methods: The study population consisted of 339 elementary school students (10–11 years of age) from the coastal and mountainous areas of Akita in 2005–2006. A questionnaire about symptoms of allergic rhinitis was filled out by the students’ parents. A blood sample was taken to determine specific IgE antibodies against five common aeroallergens. Results: The mean pollen count in the mountainous areas was two times higher than that in the coastal areas in 1996–2006. The prevalence rates of nasal allergy symptoms and sensitization for mites were almost the same in both areas. On the other hand, the rates of nasal allergy symptoms and sensitization for JC pollen were significantly higher in the mountainous areas than in the coastal areas. The rate of the development of symptoms among children sensitized for JC pollen was almost the same in both areas. Conclusions: These results suggest that pollen count levels may correlate with the rate of sensitization for JC pollinosis, but may not affect the rate of onset among sensitized children in northeast Japan.