To the Editor.
—We were intrigued by the findings of Dr Snowdon and colleagues1 in the prospective study of elderly nuns that fewer neuropathologic lesions of Alzheimer disease (AD), especially neurofibrillary tangles (NFTs), apparently resulted in dementia in individuals with concomitant lacunar infarcts than in individuals with pure AD. These observations prompted us to examine the frequency of neocortical NFTs in AD cases with and without concomitant infarcts. We reviewed data on 201 autopsy cases derived from dementia subjects clinically diagnosed as having AD enrolled in the longitudinal multicenter study, CERAD (Consortium to Establish a Registry for Alzheimer's Disease). The cases, contributed by 20 participating medical centers, were assessed using standard clinical and neuropathologic batteries. Neuropathologic assessment included semiquantitative ratings of senile plaques and NFTs in multiple regions of neocortex; levels of certainty of the neuropathologic diagnosis of AD were determined using an algorithm based on age-related neocortical plaque