Table 1:

Demographics of the sample

	N	Mean (SD) or n (%)
Age at PET scan, Mean (SD)	271	54 (8)
Age>60, n (%)		62 (23%)
Male, n (%)	271	139 (51%)
APOE4, n (%)	261	62 (24%)
Global cognition (PC1), Mean (SD)	255	0.70 (0.78)
Brainstem Measures, Mean (SD)
Medulla, % of ICV	271	0.37 (0.03)
Pons, % of ICV	271	1.22 (0.12)
Midbrain, % of ICV	271	0.50 (0.04)
PET measures (PVC)
Neocortical PiB, Median [Q1, Q3]	267	1.13 [1.09 to 1.17]*
Entorhinal FTP, Mean (SD)	238	1.20 (0.19)
Inferior Temporal FTP, Mean (SD)	238	1.31 (0.14)
Fusiform FTP, Mean (SD)	238	1.26 (0.11)
Amygdala FTP, Mean (SD)	238	1.21 (0.17)

Note:

^*: given the skewed distribution of this variable, the distribution is summarized here using the median and interquartile range.

Abbreviations: PET = Positron Emission Tomography; ICV = intracranial volume; PVC = partial volume correction; Q1 / Q3 = quartile 1/3, PiB= Pittsburgh Compound; FTP = Flortaucipir