Functional, global and cognitive decline correlates to accumulation of Alzheimer's pathology in MCI and AD

BACKGROUND

Cognitive, global and functional instruments have been extensively investigated for correlations with neuropathological changes such as neurofibrillary tangles (NFTs), plaques, and synapse loss in the brain.

OBJECTIVE

Our objective is to correlate the functional, global and cognitive decline assessed clinically with the neuropathological changes observed in a large prospectively characterized cohort of mild cognitive impairment (MCI) and Alzheimer's disease (AD).

METHODS

We examined 150 subjects (16 MCI and 134 AD) that were prospectively assessed and longitudinally followed to autopsy. MCI subjects clinically met Petersen criteria for single or multi-domain amnestic MCI. AD subjects clinically met NINCDS-ADRDA criteria for probable or possible AD. All subjects received the Functional Assessment Staging (FAST), the Global Deterioration Scale (GDS), and the Mini Mental State Examination (MMSE) ante-mortem. Plaque and tangle counts were gathered for hippocampus, entorhinal cortex, frontal, temporal and parietal cortices. Braak staging was performed as well.

RESULTS

The GDS, FAST and MMSE correlated with plaque counts in all regions. The GDS, FAST and MMSE correlated with tangle counts in in all regions. The three instruments also correlated with the Braak score. The MMSE and GDS correlate better than the FAST in most regions.

CONCLUSIONS

Accumulation of neuropathology appears to correlate with functional, global, and cognitive decline as people progress from MCI through AD.

Psychopathology among Asian Americans: a model minority?

The prevalence of psychopathology among Asian Americans has been a source of debate. Some investigators believe that the prevalence rate is quite low, whereas others argue that it is fairly high. A review of the literature suggests that at this time, it is not possible to determine the specific rates of psychopathology. However, evidence does suggest that their rates of mental disorders are not extraordinarily low. Thus, public portrayals of Asian Americans as a well-adjusted group do not reflect reality. Attempts to determine the exact prevalence rates have been hindered by characteristics of the Asian American population, particularly its relatively small size, heterogeneity, and rapid changes in demographics. It is suggested that aggregate research, in which different Asian American groups are combined, is important for policy considerations, broad cultural comparisons, and establishing baseline information. To advance scientific contributions and understanding, studies that examine the correlates and course of disorders within specific Asian American groups are necessary as well.

Soluble amyloid beta peptide concentration as a predictor of synaptic change in Alzheimer's disease

We have characterized amyloid beta peptide (Abeta) concentration, Abeta deposition, paired helical filament formation, cerebrovascular amyloid angiopathy, apolipoprotein E (ApoE) allotype, and synaptophysin concentration in entorhinal cortex and superior frontal gyrus of normal elderly control (ND) patients, Alzheimer's disease (AD) patients, and high pathology control (HPC) patients who meet pathological criteria for AD but show no synapse loss or overt antemortem symptoms of dementia. The measures of Abeta deposition, Abeta-immunoreactive plaques with and without cores, thioflavin histofluorescent plaques, and concentrations of insoluble Abeta, failed to distinguish HPC from AD patients and were poor correlates of synaptic change. By contrast, concentrations of soluble Abeta clearly distinguished HPC from AD patients and were a strong inverse correlate of synapse loss. Further investigation revealed that Abeta40, whether in soluble or insoluble form, was a particularly useful measure for classifying ND, HPC, and AD patients compared with Abeta42. Abeta40 is known to be elevated in cerebrovascular amyloid deposits, and Abeta40 (but not Abeta42) levels, cerebrovascular amyloid angiopathy, and ApoE4 allele frequency were all highly correlated with each other. Although paired helical filaments in the form of neurofibrillary tangles or a penumbra of neurites surrounding amyloid cores also distinguished HPC from AD patients, they were less robust predictors of synapse change compared with soluble Abeta, particularly soluble Abeta40. Previous experiments attempting to relate Abeta deposition to the neurodegeneration that underlies AD dementia may have failed because they assayed the classical, visible forms of the molecule, insoluble neuropil plaques, rather than the soluble, unseen forms of the molecule.