Table 1.
Descriptive Statistics
| Subset with Processing Speed Composite (N = 207) | Subset with Memory Composite (N = 178) | Subset with Executive Composite (N = 178) | Subset with Brain Structural Volumes (N = 134) | |
|---|---|---|---|---|
| Age (years) | 74.3 (6.8) | 75.5 (6.0) | 75.5 (6.0) | 75.1 (5.6) |
| Sex (% female) | 57% | 51% | 51% | 54% |
| Race (% White) | 92%a | 94%b | 94%b | 93%c |
| Education (years) | 17.5 (2.0) | 17.5 (2.1) | 17.5 (2.1) | 17.7 (2.0) |
| APOE (% ε4 carrier) | 22%d | 22% | 22% | 22% |
| SRT 30-Minute | 18.5 (1.4) | 18.4 (1.5) | 18.4 (1.5) | 18.6 (1.4) |
| SRT 1-Week | 12.8 (4.4) | 12.9 (4.4) | 12.9 (4.4) | 12.7 (4.4) |
| SRT Learning Trials | 5.1 (0.5) | 5.1 (0.5) | 5.1 (0.5) | 5.0 (0.2) |
| # participants with 2 visits | n = 207 | n = 178 | n = 178 | n = 134 |
| # participants with 3 visits | n = 89 | n = 77 | n = 85 | n = 32 |
| # participants with 4 visits | n = 10 | n = 29 | n = 35 | n = 2 |
| # participants with 5 visits | n = 3 | n = 11 | n = 13 | -- |
| # participants with 6 visits | n = 1 | n = 3 | n = 2 | -- |
| # participants with 7 visits | -- | n = 1 | n = 1 | -- |
Note. Descriptive statistics at baseline are presented as mean (standard deviation) or frequency (i.e., percentage or n) for subsets of the cohort with data available for each cognitive and brain structural outcome of interest. As shown, participants had varying numbers of study visits (2–7 visits) because the Hillblom Aging Network is an active longitudinal study with ongoing recruitment and enrollment efforts; accordingly, some participants were enrolled more recently than others and therefore had not accrued as many follow-up visits. APOE = apolipoprotein E (percentage of participants who were carriers of at least one copy of the ε4 allele). SRT = Story Recall Test. SRT 30-Minute and 1-Week = average number of story units recalled (out of 20) at the different delay periods. SRT Learning Trials = average number of learning trials required to reach the 90% mastery criterion.
N = 201;
N = 174;
N = 131;
N = 185.