A descriptive study of neuritic plaques and neurofibrillary tangles in an autopsy population.

From July 1, 1980 to December 2, 1982, all individuals at autopsy at the University of Michigan Medical Center greater than or equal to 65 years of age and selected individuals less than 65 years of age were examined for neuritic plaques and neurofibrillary tangles. Sections of the hippocampal, parahippocampal temporal gyrus, and fusiform gyrus were examined. In a total population of 199, each individual was classified as having none, few, or many of each lesion. The frequency of the joint presence of many plaques and tangles increased monotonically after age 71 years. There was no significant difference in the joint distribution of these lesions with sex or race. There was a strong correlation between the presence of one lesion and the other; the correlation for the two lesions was similar for males and females, but for blacks, it was significantly higher than for non-blacks. The distribution of these lesions in autopsy populations may be useful in identifying other related hypothetical risk factors for dementia of Alzheimer's type.