But in CTE traumatic events occur repeatedly (e.g., during boxing, football, hockey matches, or any other contact events), and after each event the baseline of the resumed accumulation of AβPP-derived iAβ is elevated further until, eventually and inevitably, the T1 threshold is crossed, the self-sustainable AβPP-independent C99/iAβ generation pathway is activated, and AD commences. This evidence concerns the gene APP and Alzheimer disease.