Entorhinal cortex beta-amyloid load in individuals with mild cognitive impairment

The deposition of beta-amyloid within the entorhinal cortex (EC) may play a key role in the development of mild cognitive impairment (MCI) in the elde rly. To examine the relationship of beta-amyloid deposition to MCI, EC tiss ue immunostained for this protein was quantitated from a cohort of aged Cat holic religious clergy with a clinical diagnosis of MCI and compared to tho se with no cognitive impairment (NCI) and Alzheimer's disease (AD). beta-am yloid staining was seen in 12 of the 20 NCI, in 10 of 12 MCI, and in all 12 AD cases within the EC. p-amyloid immunoreactivity displayed two patterns within the EC: (1) a crescent-shaped band within layers 3-4 or (2) bilamina r staining mainly within layers 2-3 and 5-6. Ten cases failed to display an y detectable beta-amyloid imunoreactivity. Despite the heterogeneity of bet a-amyloid loads within the clinical groups, decomposing an analysis of vari ance revealed a significant difference across groups in mean beta-amyloid l oad within the EC based upon a linear trend analysis. Multiple comparisons testing revealed that NCI individuals had a significantly lower mean beta-a myloid load (1.32) than AD individuals (4.55). The MCI individuals had a me an intermediate (2.60) load be tween NCI and AD, but not statistically dist inguishable from the mean for either NCI or AD. Spearman rank correlation s howed a trend for decreasing MMSE with increasing amyloid load that failed to reach statistical significance. Since many NCI cases displayed beta-amyl oid loads equal to or greater than that seen in some MCI and some AD cases, it is mostly likely that deposition of this protein is not the sole pathog enic event underlying cognitive impairment in the elderly. (C) 1999 Academi c Press.