Aging and APOE-ε4 are determinative factors of plasma A β 42 levels.

OBJECTIVE: The aim of this study was to confirm determinative factors for plasma A β and its association with cognitive function.

METHODS: Fasting plasma A β 40 and A β 42 levels were measured by ELISA in 1019 participants in the Iwaki Health Promotion Project. The relationships between plasma A β and health-related items, including physical characteristics, cognitive function tests, blood chemistry, and APOE-ε4 genotype were analyzed.

RESULTS: The plasma levels of A β 40 and A β 42, and A β 40/42 ratio were found to significantly increase with aging. The age-dependent increase in A β 42 level was significantly suppressed by APOE-ε4 . Renal function was an associated factor for the plasma A β 40 level. The plasma A β 42 level and A β 40/42 ratio correlated with cognitive function.

INTERPRETATION: Age and APOE-ε4 are major determinative factors of plasma levels of A β 42 and the A β 40/42 ratio. These factors are critical adjustment factors for the usage of plasma A β as a biomarker of central nervous system amyloidosis.