Table 14.
Parameter estimates from the linear mixed-effects models for gray and white ROI volumetric measures adjusted for total brain volumea
| Frontal |
Prefrontal |
Cingulate |
Temporal limbic |
|||||
|---|---|---|---|---|---|---|---|---|
| Model term | Estimate (SE) | p | Estimate (SE) | p | Estimate (SE) | p | Estimate (SE) | p |
| GM volume | ||||||||
| Intercept | 7518.4 (95.9) | <0.001 | 7131.8 (101.5) | <0.001 | 2297.9 (26.6) | <0.001 | 2445.6 (28.0) | <0.001 |
| Difference (mm3) MIA vs Control | −403.3 (140.9)b | 0.01b | −387.6 (154.6)b | 0.02b | 0.9 (41.1) | 0.98 | 82.2 (44.7) | 0.08 |
| Difference (mm3) Time 2 vs Time 1 | −91.5 (31.9) | 0.007 | −257.5 (23.4) | <0.001 | −59.5 (10.8) | <0.001 | 200.7 (16.1) | <0.001 |
| Difference (mm3) Time 3 vs Time 1 | −163.6 (57.2) | 0.006 | −645.5 (51.6) | <0.001 | −193.2 (19.1) | <0.001 | 367.5 (25.9) | <0.001 |
| Difference (mm3) Time 4 vs Time 1 | −299.8 (58.9) | <0.001 | −941.0 (64.7) | <0.001 | −282.2 (22.1) | <0.001 | 350.8 (33.5) | <0.001 |
| Difference (mm3) Time 5 vs Time 1 | −410.9 (78.3) | <0.001 | −1161.8 (74.3) | <0.001 | −337.6 (27.3) | <0.001 | 329.3 (34.2) | <0.001 |
| Brain volume (cm3) | 93.3 (6.0) | <0.001 | 90.7 (5.6) | <0.001 | 26.7 (2.1) | <0.001 | 24.5 (2.4) | <0.001 |
| WM volume | ||||||||
| Intercept | 2775.1 (42.7) | <0.001 | 1656.1 (33.7) | <0.001 | 361.5 (8.3) | <0.001 | 441.6 (7.9) | <0.001 |
| Difference (mm3) MIA vs Control (at Time 1) | −50.1 (63.4) | 0.44 | 49.3 (44.1) | 0.28 | −4.4 (11.2) | 0.70 | 9.2 (11.3) | 0.42 |
| Difference (mm3) Time 2 vs Time 1 (in Control) | 303.4 (18.0) | <0.001 | 246.5 (12.0) | <0.001 | 24.7 (2.8) | <0.001 | 26.6 (3.0) | <0.001 |
| Difference (mm3) Time 3 vs Time 1 (in Control) | 676.6 (39.7) | <0.001 | 511.4 (24.9) | <0.001 | 68.8 (5.7) | <0.001 | 79.9 (5.3) | <0.001 |
| Difference (mm3) Time 4 vs Time 1 (in Control) | 1000.3 (46.3) | <0.001 | 678.4 (30.8) | <0.001 | 102.4 (6.8) | <0.001 | 104.3 (6.6) | <0.001 |
| Difference (mm3) Time 5 vs Time 1 (in Control) | 1207.2 (55.9) | <0.001 | 758.9 (37.0) | <0.001 | 116.2 (8.1) | <0.001 | 119.2 (7.4) | <0.001 |
| Difference between groups in Time 2 vs Time 1 differences | −52.8 (23.1) | 0.03 | — | — | — | — | — | — |
| Difference between groups in Time 3 vs Time 1 differences | −88.9 (44.1) | 0.06 | — | — | — | — | — | — |
| Difference between groups in Time 4 vs Time 1 differences | −136.8 (52.3) | 0.02 | — | — | — | — | — | — |
| Difference between groups in Time 5 vs Time 1 differences | −214.0 (61.7) | 0.002 | — | — | — | — | — | — |
| Brain volume (cm3) | 28.6 (3.2) | <0.001 | 18.7 (2.1) | <0.001 | 3.4 (0.6) | <0.001 | 4.6 (0.5) | <0.001 |
aTime 1 = 6 months; Time 2 = 12 months; Time 3 = 24 months; Time 4 = 36 months; Time 5 = 45 months. Mixed-effects linear regression models were fitted to 13 MIA (1 missing at 45 months) and 14 control animals and included fixed effects for group, time, and their interaction, brain volume, with unstructured covariance within animal. Interactions were not retained in the reported models if the overall test for time × group was nonsignificant. If the interaction is not included, the estimated difference between MIA versus Control is the same across time points, and the estimated difference between time points is the same within MIA and Control. If the interaction is included, difference between MIA versus Control is the estimated difference at Time 1 and the estimated differences between time points are for the Control group. Brain volume was lefted at 86,200; thus, the intercept can be interpreted as the predicted volume (in mm3) at Time 1 for a Control animal with a brain of 86,200 mm3. The estimate for brain volume can be interpreted as the average increase in ROI volume (in mm3) for a 1 cm3 increase in brain volume.
bStatistically significant MIA versus Control group difference (p < 0.05).