P3-088: 30 months prospective study on plasma amyloid beta protein 42, medial temporal lobe atrophy and change of cognition in the VITA cohort

Abstract

The comparison of plasma amyloid beta (Aβ42) with morphological and neuropsychological measurements might improve our understanding of transition from cognitive health to mild cognitive impairment (MCI) and Alzheimer's disease (AD). To compare plasma Aβ42, medial temporal atrophy (MTA) and cognitive performance in groups of persons remaining cognitively healthy, or developing MCI, or AD. Longitudinal, 30 months follow up, community–based study of 606 individuals aged 75 years at entry participating in the Vienna Transdanube Aging study (VITA). Plasma Aβ42 measured at baseline did not predict which persons remain cognitively healthy and which develop MCI or AD after 30 months. In contrast, higher scores on the MTA–scale at baseline distinguished significantly between the latter groups. By using plasma Aβ42 change over time, we corroborate previous studies showing that also the group of persons remaining cognitively healthy increased their Aβ42 plasma level. The increase of Aβ42 significantly distinguished between persons remaining cognitively healthy and those who developed MCI and AD out of cognitive health. The increases of Aβ42 levels in AD–converters out of cognitive health tended to be similar to that of MCI–converters out of cognitive health but not similar to the AD–converters out of MCI at baseline. Compared to all cognitive subgroups, the latter group showed the smallest increase of Aβ42 levels. In multiple testing, plasma Aβ42, but not MTA in MCI–converters and MTA, but not Aβ42 in AD–converters out of cognitive health were significantly increased. The increase of plasma Aβ42 correctly allocated MCI– and AD–converters out of cognitive health with low (63%) specificity (for both) and low (60%) sensitivity (54% for AD group). Regardless of cognition, the increase of Aβ42 significantly distinguished between persons remaining normal and those who developed a low degree of MTA. Our data indicate that plasma Aβ42 on its own is not suitable as a diagnostic marker for early detection of AD. However, we suggest that for the development of MCI, the increase of Aβ42 is a better distinguishing parameter than MTA and reciprocally for the development of AD out of cognitive health, the increase of MTA and less Aβ42.