Aging and APOE‐ε4 are determinative factors of plasma Aβ42 levels

OBJECTIVE: The aim of this study was to confirm determinative factors for plasma Aβ and its association with cognitive function. METHODS: Fasting plasma Aβ40 and Aβ42 levels were measured by ELISA in 1019 participants in the Iwaki Health Promotion Project. The relationships between plasma Aβ and health‐related items, including physical characteristics, cognitive function tests, blood chemistry, and APOE‐ε4 genotype were analyzed. RESULTS: The plasma levels of Aβ40 and Aβ42, and Aβ40/42 ratio were found to significantly increase with aging. The age‐dependent increase in Aβ42 level was significantly suppressed by APOE‐ε4. Renal function was an associated factor for the plasma Aβ40 level. The plasma Aβ42 level and Aβ40/42 ratio correlated with cognitive function. INTERPRETATION: Age and APOE‐ε4 are major determinative factors of plasma levels of Aβ42 and the Aβ40/42 ratio. These factors are critical adjustment factors for the usage of plasma Aβ as a biomarker of central nervous system amyloidosis.