Relationship Between Annual Airbornepollen Levels (1974–2014) and the Occurrence of Idiopathic Dilated Cardiomyopathy, Myasthenia Gravis, Polymyositis/ Dermatomyositis, and Vasculitis Syndrome Based on the National Registry Database of Specific Intractable Disease in Japan: A Retrospective Study

Background: In Japan, pollen counts increased between 1977 and 1987, including three peaks (1978-1980, 1982, 1984-1986) coinciding with Kawasaki disease (KD) outbreaks. KD and related diseases may be related to pollen exposure (PE). Methods and Results: To elucidate the effects of PE on outbreaks of intractable muscular diseases and vasculitis syndromes, we evaluated the annual occurrence of disorders in relation to pollen counts using data from a national database. Specifically, we evaluated the occurrence of idiopathic dilated cardiomyopathy (IDCM), myasthenia gravis (MG), polymyositis/dermatomyositis (PM/DM), Takayasu arteritis (TAK), granulomatosis with polyangiitis (GPA), and periarteritis nodosa (PAN). While we did not observe increased disease rates during the first pollen count peak (1978-1980), increased rates of all evaluated diseases were observed during the 1982 and 1984-86 peaks. Furthermore, simultaneous outbreaks coincided with 10pollen count peaks between 1988 and 2013. We observed significant correlations between the annual number of newly registered patients (nRPs) with IDCM, MG, PM/DM, and PAN and annual pollen levels (PL). Significant correlations were also observed between nRPs and the annual PL measured with a lag of 2 years for IDCM and GPA, 1–4 years for PAN, and 6 years for MG, PM/DM, TAK, GPA, and PAN. Conclusion: Data suggest that the cumulative effects of PE within 6 years prior to diagnosis might possibly trigger onset of muscular specific intractable diseases.