Analysis of Natural History of Japanese Cedar Pollinosis

Abstract

Background: The marked increase in the incidence of Japanese cedar (Cryptomeria japonica; JC) pollinosis is a social problem in Japan. Elucidation of its natural history is, therefore, essential. Methods: Cross-sectional and vertical-sectional studies were performed regarding the effects of aging on sensitization to Japanese cedar pollen (JCP) and development of JC pollinosis by measuring serum IgE titers to JCP and by oral examination of residents of the Maruyama Town, Chiba, Japan from 1995 to 2001. We also studied the incidence of its spontaneous remission and the background factors. Results: In a vertical-sectional study, the serum IgE titer to JCP was strongly influenced by the amounts of pollen scattered. An increase in age by 6 years did not reduce the IgE titer to JCP in subjects in their 40s. However, in subjects aged 60 or more, annual differences in the JCP count did not affect serum IgE titer to JCP, which remained low even after a season with a high pollen count. In subjects with JC pollinosis aged over 40 showing a CAP RAST score of more than 2 to JCP in 1995, spontaneous remission of JC pollinosis was observed in 16.1% over a period of 6 years. Factors affecting spontaneous remission include sex, age at the time, serum IgE titer to JCP and age at first onset of JC pollinosis. Conclusions: The CAP RAST score was strongly associated with spontaneous remission in the multivariable model.