Table 1. Characteristics of the Participantsa.
| Value | Mean (SD) | 95% CI | P Value | ||
|---|---|---|---|---|---|
| All (N = 60) | Low PiB (n = 43) | High PiB (n = 17) | |||
| Age at inclusion, t = −3, y | 73.1 (6.0) | 72.6 (6.1) | 74.4 (5.5) | −1.6 to 5.2 | .29 |
| Education, y | 15.6 (3.2) | 15.4 (3.4) | 16.1 (2.7) | (−1.2 to 2.4 | .50 |
| Female, No. (%) | 35 (58.3) | 24 (55.8) | 11 (64.7) | NA | .54 |
| ε4 Carriers, No. (%) | 20 (33.9) | 8 (19.0) | 12 (70.6) | NA | <.001 |
| Missing | 1 | 1 | 0 | NA | NA |
| Initial PiB: t = −3, SUVr | 0.66 (0.31) | 0.49 (0.09) | 1.11 (0.20) | 0.53 to 0.68 | <.001 |
| Missing | 10 | 8 | 2 | ||
| Baseline PiB: t = 0, SUVr | 0.71 (0.34) | 0.52 (0.13) | 1.20 (0.17) | 0.59 to 0.77 | <.001 |
| Final PiB: t = 2, SUVr | 0.74 (0.36) | 0.53 (0.14) | 1.27 (0.16) | 0.65 to 0.82 | <.001 |
| Annual PiB change | |||||
| Period 1: t = −3 to t = 0 | 0.01 (0.01) | 0.01 | 0.02 (0.01) | 0.01 to 0.02 | <.001 |
| 95% CIb | 0.01 to 0.02 | 0.00 to 0.01 | 0.02 to 0.03 | NA | NA |
| CoV, SUVr/y | 0.8 | 0.9 | 0.4 | NA | |
| Missing | 10 | 8 | 2 | NA | |
| Period 2: t = 0 to t = 2 | 0.01 (0.02) | 0.01 (0.02) | 0.03 (0.03) | 0.02 to 0.04 | <.001 |
| 95% CIb | 0.01 to 0.02 | 0.00 to 0.01 | 0.02 to 0.05 | NA | |
| CoV, SUVr/y | 1.6 | 2.7 | 0.7 | NA | |
| Baseline FTP: t = 0, SUVr | 1.29 (0.18) | 1.24 (0.12) | 1.43 (0.24) | 0.10 to 0.28 | <.001 |
| Final FTP: t = 2, SUVr | 1.38 (0.23) | 1.31 (0.12) | 1.55 (0.34) | 0.12 to 0.35 | <.001 |
| Annual FTP change | |||||
| Period 2: t = 0 to t = 2 | 0.04 (0.03) | 0.03 (0.03) | 0.05 (0.04) | 0.001 to 0.04 | .04 |
| 95% CIb | 0.03 to 0.05 | 0.03 to 0.04 | 0.03 to 0.08 | NA | |
| CoV, SUVr/y | 0.8 | 0.7 | 0.8 | NA | |
| Initial PACC: t = −3, z score | −0.06 (0.88) | −0.09 (0.95) | 0.00 (0.72) | −0.52 to 0.61 | .87 |
| Baseline PACC: t = 0, z score | 0.00 (1.00) | 0.10 (1.02) | −0.25 (0.93) | −0.92 to 0.22 | .23 |
| Final PACC: t = 3, z score | −0.31 (1.40) | 0.03 (1.06) | −1.18 (1.64) | −1.96 to −0.47 | .002 |
| Annual PACC change | |||||
| Period 1: t = −3 to t = 0 | 0.05 (0.07) | 0.06 (0.06) | 0.01 (0.08) | −0.09 to −0.01 | .02 |
| 95% CIb | 0.03 to 0.07 | 0.04 to 0.08 | −0.03 to 0.08 | NA | |
| CoV, SD/y | 1.5 | 1.0 | 5.9 | NA | |
| Period 2: t = 0 to t = 3 | −0.10 (0.23) | −0.05 (0.16) | −0.25 (0.31) | −0.32 to −0.08 | .002 |
| 95% CIb | −0.16 to −0.05 | −0.10 to −0.00 | −0.41 to −0.09 | NA | |
| CoV, SD/y | 2.2 | 3.2 | 1.3 | NA | |
Abbreviations: CoV, coefficients of variation; ε4, epsiolon allele; FTP, flortaucipir; NA, not applicable; PACC, Preclinical Alzheimer Cognitive Composite; PET, positron emission tomography; PiB, Pittsburgh compound B; SUVr, standardized uptake value ratios; t, time in years from baseline.
Participants with low and high PiB are compared using t tests (χ2 for ε4 genotype and sex). The 95% CIs are provided for the difference between PiB groups (last column). The 95% CI within groups are also provided for change data to assess whether they significantly differed from zero. Coefficients of variation (CoV = SD of change divided by mean change) are provided for PET and PACC changes. Change data are slopes extracted from separate linear mixed-effect models measuring PiB, FTP, and PACC over time with a random intercept and time slope per participant.
P < .05.