Neurofibrillary tangle burden is determined by microscopic examination of silver-stained slides from 5 regions: midfrontal cortex, midtemporal cortex, inferior parietal cortex, entorhinal cortex, and hippocampus. The count of each region is scaled by dividing by the corresponding standard deviation. The 5 scaled regional measures are then averaged to obtain a summary measure for neurofibrillary tangle burden.

Neurofibrillary tangle pathology counts by region:

Notes: Counts of tangles may be missing for regions (e.g., due to damage from infarct). If data are present for at least 2 of 5 regions, the summary measure for neurofibrillary tangle burden is computed.

Item level variables are available upon request.