In 2020, we reported that rates of change in an amyloid summary index are broadly linear above the positivity threshold and increasing in a predictable manner such that both age of onset of amyloid positivity and the chronicity of the disease (defined as the time-span in years of amyloid positivity) can be feasibly estimated from a single scan.(20) We further showed in that report that preclinical cognitive decline and tau-related PET signal were more likely to be observed with longer amyloid duration. The gene discussed is MAPT; the disease is Mental deterioration.