MAPT and early-onset autosomal dominant Alzheimer disease: In contrast, some other studies did find elevated Aβ and tau associated with TBI.49-61 However, a closer examination of these previous studies reveals that these effects were predominantly observed in individuals with cognitive impairment,49,51,54,56,57,62 with positive Aβ biomarkers,51,62 or in homozygous APOEɛ4 carriers.54 Specifically, these earlier findings suggest that TBI might accelerate Alzheimer’s disease–related processes particularly in individuals already predisposed or vulnerable to Alzheimer’s disease.