The distribution of each IgG subclass showed significant or marginally significant differences among 5 groups by analysis of variance, therefore we studied the details to clarify the characteristics of narcolepsy patients with low total IgG levels and idiopathic hypersomnia patients with long sleep time as follows; IgG1: The mean IgG1 levels were significantly lower in narcolepsy patients with low total IgG levels than in HLA-negative controls (p<0.005), HLA-positive controls (p<0.01), narcolepsy patients with normal total IgG levels (p<0.01), and idiopathic hypersomnia patients (p<0.005) ( Table 2 , Fig. 2 ).
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