MAPT and Alzheimer disease: We also found that the abundance of tau prions had a modest linear correlation with the abundance of Aβ prions (R2 = 0.2474; P = 0.0071) in people with DS (Fig. 1C), which was consistent with the AD neuropathology scores (SI Appendix, Fig. S2C) and biochemical measurements (SI Appendix, Fig. S2F).