We assessed the prevalence of common altered brain proteins in 296 cognitively unimpaired subjects ranging from age 50 to 102 years. The incidence and the stage of hyperphosphorylated-tau (HP tau), beta-amyloid, alpha-synuclein (alpha S), and transactive response DNA (TDP) binding protein 43 (TDP43)-immunoreactivity (-IR) increased with age. HP tau-IR was observed in 98% of the subjects; the locus coeruleus was solely affected in 46%, and 79% of the subjects were in Braak stages a to II. beta-Amyloid was seen in 47% of subjects and the Thal phase correlated with the HP tau Braak stage and age. Intermediate Alzheimer disease-related pathology (ADRP) was seen in 12%; 52% of the subjects with HP tau-IR fulfilled criteria for definite primary age-related tauopathy (PART). The incidence of concomitant pathology (alpha S, TDP43) did not differ between those with PART and those with ADRP but the former were younger. TDP43-IR was observed in 36%; the most frequently affected region was the medulla; alpha S-IR was observed in 19% of subjects. In 41% of the subjects from 80 to 89 years at death, 3 altered proteins were seen in the brain. Thus, altered proteins are common in the brains of cognitively unimpaired aged subjects; this should be considered while developing diagnostic biomarkers, particularly for identifying subjects at early stages of neurodegenerative diseases.
