Clinical and pathological correlates of apolipoprotein E ε4 in Alzheimer's disease

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Abstract
Inheritance of the apolipoprotein E (apoE) ε4 allele is associated with a high likelihood of developing Alzheimer's disease (AD). The pathophysiologic basis of this genetic influence is unknown. We reasoned that understanding the influence of apoE ε4 on the clinical course and neuropathological features of AD may provide tests of potential mechanisms. We carried out a prospective longitudinal study to compare the age of onset, duration, and rate of progression of 359 AD patients to apoE genotype. Thirty‐one of the individuals who died during the study were available for quantitative neuropathological evaluation. Statistically unbiased stereological counts of neurofibrillary tangles (NFTs) and Aβ deposits were assessed in a high‐order association cortex, the superior temporal sulcus. Analysis of clinical parameters compared with apoE genotype showed that the ε4 allele is associated with an earlier age of onset but no change in rate of progression of dementia. Quantitative neuropathological assessment revealed that NFTs were strongly associated with clinical measures of dementia duration and severity but not with apoE genotype. Aβ deposition, by contrast, was not related to clinical features but was elevated in association with apoE ε4. These results indicate that apoE ε4 is associated with selective clinical and neuropathological features of AD and support hypotheses that focus on an influence of apoE ε4 on amyloid deposition.