IDH1 and oligoastrocytoma: IDH1 SNV mutation frequency was negatively associated with age in astrocytoma (Wilcox p = 1.3 × 10−8) and oligoastrocytoma (Wilcox p = 0.041), but not oligodendroglioma (Wilcox p = 0.19), and we found significant age-IDH1 interactions in mRNA abundance analysis for oligodendroglioma (interaction p = 0.038) and oligoastrocytoma (interaction p = 6.2 × 10−3).