Table 2.
Variance in cortical structure at age 6 accounted for by earlier ages.
| Singletons | Twins | ||||||
|---|---|---|---|---|---|---|---|
| r2 | CI | N | r2 | CI | N | ||
| Year 0 | WM | 0.25 | (0.05, 0.53) | 52 | 0.27 | (0.05, 0.58) | 45 |
| GM | 0.46 | (0.26, 0.66) | 52 | 0.45 | (0.22, 0.69) | 45 | |
| Year 1 | WM | 0.55 | (0.30, 0.76) | 51 | 0.61 | (0.41, 0.77) | 48 |
| GM | 0.87 | (0.78, 0.94) | 51 | 0.81 | (0.64, 0.93) | 48 | |
| SA | 0.83 | (0.72, 0.91) | 49 | 0.73 | (0.52, 0.88) | 46 | |
| CT | 0.13 | (0.00, 0.40) | 49 | 0.37 | (0.08, 0.76) | 46 | |
| Year 2 | WM | 0.60 | (0.31, 0.82) | 40 | 0.70 | (0.49, 0.87) | 40 |
| GM | 0.83 | (0.67, 0.94) | 40 | 0.83 | (0.65, 0.93) | 40 | |
| SA | 0.91 | (0.82, 0.97) | 40 | 0.78 | (0.53, 0.90) | 38 | |
| CT | 0.45 | (0.13, 0.75) | 40 | 0.59 | (0.31, 0.85) | 38 | |
| Year 4 | WM | 0.87 | (0.74, 0.96) | 55 | 0.93 | (0.85, 0.98) | 32 |
| GM | 0.90 | (0.76, 0.97) | 55 | 0.97 | (0.93, 0.99) | 32 | |
| SA | 0.66 | (0.41, 0.92) | 52 | 0.93 | (0.85, 0.98) | 30 | |
| CT | 0.00 | (0.00, 0.16) | 52 | 0.55 | (0.20, 0.86) | 30 | |
Separate models were used to generate residual cortical GM, WM, average CT, and total SA for neonate, 1, 2, and 4 year scans adjusting for motion rating, scanner and age at scan (in days). Residual cortical measures were then entered as independent variables in a linear model to estimate cortical GM and WM at age 6. Covariates in these models were birthweight, gestational age at birth, sex, mother’s education (in years), height at 6, weight at 6, scanner for the age 6 scan, age in days for the age 6 scan, and motion score for the age 6 scan. A confidence interval for the partial r-squared was determined from 1,000 bootstrap samples using the percentile method.