Table 1.
Study sample characteristics.
| All Participants | Leptin, pg/mL** [Median (Minimum-Maximum)] |
P-value† | ||||
|---|---|---|---|---|---|---|
| Quartile 1 [Females: 4365 (793–6873) Males: 1633 (322–2445)] |
Quartile 2 [Females: 9420 (6898–12,443) Males: 3365 (2445–4358)] |
Quartile 3 [Females: 16,746 (12,445–23,620) Males: 5551 (4369–7735)] |
Quartile 4 [Females: 36,175 (23,654–101,539) Males: 11,407 (7771–64,214)] |
|||
| N=2223 | N=555 | N=556 | N=557 | N=555 | ||
| Female sex | 1169 (52.6) | 292 (52.6) | 292 (52.5) | 293 (52.6) | 292 (52.6) | 0.99 |
| Age at clinic exam, years | 40.4 (8.6) | 38.7 (8.0) | 39.7 (8.7) | 40.8 (8.8) | 42.3 (8.4) | <0.0001 |
| Age at NP/MRI, years | 48.2 (8.7) | 46.4 (8.4) | 47.5 (8.8) | 48.6 (8.9) | 50.1 (8.6) | <0.0001 |
| Years between clinic exam and NP/MRI | 7.8 (1.1) | 7.8 (1.0) | 7.7 (1.0) | 7.8 (1.1) | 7.8 (1.1) | 0.73 |
| Education level | ||||||
| High school degree or less | 324 (14.6) | 73 (13.2) | 80 (14.4) | 70 (12.6) | 101 (18.2) | 0.0004 |
| Some college | 531 (23.9) | 111 (20.0) | 124 (22.3) | 139 (25.0) | 157 (28.3) | |
| College degree or more | 1368 (61.5) | 371 (66.9) | 352 (63.3) | 348 (62.5) | 297 (53.5) | |
| APOE4, n (%) | 471 (22.2) | 113 (21.7) | 117 (21.7) | 113 (21.3) | 128 (24.3) | 0.63 |
| Systolic blood pressure, mm Hg | 117 (14) | 112 (12) | 115 (13) | 118 (13) | 123 (15) | <0.0001 |
| Hypertension treatment | 174 (7.9) | 13 (2.3) | 30 (5.4) | 44(7.9) | 87 (15.8) | <0.0001 |
| Current smoker | 297 (13.4) | 87 (15.7) | 75 (13.5) | 57 (10.2) | 78 (14.1) | 0.06 |
| Body mass index, kg/m2 | 27.0 (5.3) | 22.9 (2.5) | 24.9 (3.1) | 27.2 (3.3) | 32.9 (5.6) | <0.0001 |
| BMI category, n (%) | ||||||
| 18.5–24.9 | 891 (40.1) | 433 (78.0) | 299 (53.8) | 140 (25.1) | 19 (3.4) | <0.0001 |
| 25.0–29.9 | 832 (37.4) | 122 (22.0) | 229 (41.2) | 314 (56.4) | 167 (30.1) | |
| ≥30.0 | 500 (22.5) | 0 (0.0) | 28 (5.0) | 103 (18.5) | 369 (66.5) | |
| Diabetes | 54 (2.4) | 5 (0.90) | 11 (2.0) | 9 (1.6) | 29 (5.2) | <0.0001 |
| Waist circumference, in | 36.3 (32.5, 40.0) | 32.0 (29.8, 34.8) | 34.5 (31.5, 37.3) | 37.3 (34.8, 39.8) | 42.3 (38.8, 45.8) | <0.0001 |
| Fasting blood glucose, mg/dL | 92 (87, 98) | 90 (85, 94) | 91 (87, 97) | 94 (89, 99) | 96 (91, 103) | <0.0001 |
| Insulin, pM/L | 23.9 (17.0, 35.6) | 16.4 (12.2, 21.9) | 21.5 (16.3, 28.4) | 26.9 (20.2, 36.7) | 38.3 (26.8, 53.2) | <0.0001 |
| Leptin, pg/mL | 7498 (3760, 15,123) | 2343 (1590, 4472) | 7031 (3420, 9480) | 12,966 (5588, 17,028) | 25,074 (11,564, 38,570) | --- |
| Neuropsychological test score | ||||||
| Logical Memory - Delayed | 11.5 (3.7) | 11.4 (3.8) | 11.6 (3.8) | 12.0 (3.7) | 11.1(3.6) | 0.0008 |
| Visual Reproductions - Delayed | 8.9 (2.6) | 9.2 (2.5) | 9.0 (2.6) | 8.8 (2.7) | 8.5 (2.7) | 0.0002 |
| Hooper’s Visual Organization Test | 27.0 (25.5, 28.0) | 26.5 (25.5, 28.0) | 27.0 (25.5, 28.0) | 27.0 (25.5, 28.0) | 27.0 (25.5, 28.0) | 0.65 |
| Digit Span Forwards | 6.9 (1.3) | 6.9 (1.2) | 7.0 (1.3) | 6.9 (1.3) | 6.7 (1.3) | 0.03 |
| Digit Span Backwards | 5.1 (1.3) | 5.3 (1.3) | 5.1 (1.3) | 5.1 (1.3) | 5.1 (1.3) | 0.01 |
| Trails B – Trails A | 0.53 (0.38. 0.73) | 0.53 (0.38, 0.73) | 0.52 (0.38, 0.70) | 0.53 (0.38, 0.73) | 0.56 (0.41, 0.73) | 0.16 |
| Similarities | 17.3 (3.1) | 17.4 (3.0) | 17.5 (3.0) | 17.2 (3.1) | 17.1 (3.2) | 0.08 |
| Boston Naming Test (30 item) | 28.0 (27.0, 29.0) | 28.0 (27.0, 29.0) | 28.0 (26.0, 29.0) | 28.0 (27.0, 29.0) | 28.0 (27.0, 29.0) | 0.81 |
| MRI Brain Volume Measures | N=2011 | N=523 | N=505 | N=504 | N=497 | |
| Total cerebral brain volume*, % | 79.0 (1.9) | 79.2 (1.8) | 79.1 (1.7) | 79.0 (2.0) | 78.8 (2.1) | 0.003 |
| Total gray matter volume*, % | 49.9 (2.0) | 50.1 (2.1) | 50.1 (2.1) | 50.0 (1.9) | 49.6 (2.1) | 0.002 |
| Total white matter volume*, % | 40.9 (2.1) | 41.0 (2.1) | 40.9 (2.1) | 40.9 (2.2) | 40.8 (2.2) | 0.83 |
| Hippocampal volume*, % | 0.54 (0.045) | 0.54 (0.044) | 0.54 (0.045) | 0.54 (0.045) | 0.55 (0.045) | 0.36 |
| White matter hyperintensities, cm3 | 0.41 (0.21, 0.86) | 0.36 (0.18, 0.74) | 0.38 (0.20, 0.79) | 0.43 (0.23, 0.86) | 0.48 (0.24, 1.03) | 0.0001 |
Note: The numbers in the table represent mean (SD) for continuous, normally distributed variables, median (25th, 75th percentile) for continuous non-normally distributed variables, and n (%) for categorical variables.
*
Expressed as a percentage of total cranial volume.
**
Sex-specific quartiles of natural log-transformed leptin.
†
Calculated using a Chi-square test (categorical variables), ANOVA (continuous, normally distributed variables), or Kruskall-Wallis test (continuous, non-normally distributed variables)