Table 3.
Neuropsychological and Magnetic Resonance Imaging Summary Statistics
| Total Sample | Normal Cognition | MCI | Dementia | P* | |
|---|---|---|---|---|---|
| Functional Severity | |||||
| CDR Sum of Boxes, mean (SD) | 1.58 (2.39) | .09 (.33) | 1.35 (1.11) | 4.73 (2.60) | <.001 |
| Neuropsychological test raw scores, mean (SD)** | |||||
| Mini-Mental State Examination | 27.08 (3.53) | 28.97 (1.34) | 27.25 (2.31) | 23.18 (4.24) | <.001 |
| Trail Making Test Part A | 43.12 (25.60) | 33.97 (14.66) | 43.23 (21.23) | 61.11 (35.11) | <.001 |
| Trail Making Test Part B | 131.68 (83.59) | 89.67 (48.72) | 138.37 (75.98) | 208.27 (88.71) | <.001 |
| Digit Span Forward | 8.07 (2.13) | 8.60 (2.00) | 7.90 (2.04) | 7.18 (2.16) | <.001 |
| Digit Span Backward | 6.09 (2.27) | 6.84 (2.21) | 5.84 (2.03) | 4.83 (1.96) | <.001 |
| WAIS-R Digit Symbol | 35.70 (21.84) | 41.07 (22.65) | 33.35 (19.52) | 27.32 (19.10) | <.001 |
| Logical Memory Immediate Recall | 10.42 (5.27) | 13.58 (3.83) | 9.31 (4.21) | 5.24 (3.93) | <.001 |
| Logical Memory Delayed Recall | 8.70 (5.79) | 12.38 (4.14) | 7.16 (4.70) | 2.92 (3.78) | <.001 |
| Animal Fluency | 17.24 (6.42) | 20.50 (5.61) | 16.15 (4.95) | 11.86 (5.05) | <.001 |
| Vegetable Fluency | 12.07 (5.00) | 14.75 (4.26) | 11.09 (3.83) | 7.69 (3.76) | <.001 |
| Boston Naming Test | 25.15 (5.34) | 27.32 (3.02) | 24.93 (4.58) | 21.07 (6.94) | <.001 |
| MRI-derived indices, mean (SD)*** | |||||
| Total brain volume, cm3 | 1015.11 (111.21) | 1026.50 (113.18) | 1004.78 (104.78) | 989.48 (109.85) | <.001 |
| Hippocampal volume, cm3 | 6.09 (0.90) | 6.39 (0.75) | 5.78 (0.88) | 5.48 (1.01) | <.001 |
| Log-transformed white matter hyperintensities, cm3 | 0.49 (0.71) | 0.29 (0.73) | 0.75 (0.56) | 0.82 (0.56) | <.001 |
Analysis of variance compared the diagnostic groups on the neuropsychological test scores, CDR Sum of Boxes, and the MRI-derived structural indices. There were statistically significant differences between each of the diagnostic groups across all variables (i.e., normal cognition > MCI > dementia), with the exception of no statistically significant difference between MCI and dementia for total brain volume and log-transformed white matter hyperintensities.
Of the 19,309 participants, 7,740 were administered Uniform Data Set (UDS) version 1.0., 9,013 were administered version 2.0, and 2,556 were administered version 3.0. For UDS version 3.0, a new neuropsychological test battery was adopted and a subset of instruments were replaced with similar but non-proprietary tests. Equipercentile equating methods were used to convert scores on UDS version 3.0 tests to comparable scores on the respective UDS version 2.0 test that was replaced. To maximize the sample size and available data, the conversion scores for the MMSE, Logical Memory, Digit Span Forward and Backward, and Boston Naming Test were used for those participants who were administered the UDS version 3.0 battery. Refer to the Methods section under Neuropsychological Measures for further details. Sample size for MRI indices was 1,196.
Abbreviations: MCI = mild cognitive impairment; WAIS-R = Wechsler Adult Intelligence Scale, Revised Version; CDR = CDR Dementia Staging Instrument; MRI = magnetic resonance imaging; SD = standard deviation