MAPT and Alzheimer disease: Although no significant relationship between any two AD biomarkers was detected in the middle-aged groups, e.g., the 3rd and 4th decades of life, positive correlations between Aβ42 and t-Tau were detected from the 6th to 9th decades; negative correlations were detected between Aβ40 and Aβ42 in age groups from the 4th, 6th, and 7th decades and between Aβ40 and t-Tau during the 5th to 8th decades.