Table 1.
Mean differences (95% confidence intervals) in standardised cognitive score by birthweight group compared with middle birthweight group (3.01-3.50 kg) for all cognitive tests and results of statistical tests for heterogeneity across categories of birth weight
| Test age (years) | Birth weight (kg)
|
P value (and for normal birth weight) | ||||
|---|---|---|---|---|---|---|
| Low (0-2.50) | Normal
|
|||||
| 2.51-3.00 | 3.51-4.00 | 4.01-5.00 | ||||
| 8 (n=3773) | −0.27 (−0.42 to −0.11) | −0.06 (−0.16 to 0.03) | 0.13 (0.05 to 0.21) | 0.03 (−0.08 to 0.14) | <0.001 (<0.001) | |
| 11 (n=3618) | −0.23 (−0.39 to −0.06) | −0.09 (−0.18 to 0.01) | 0.08 (0.00 to 0.15) | −0.08 (−0.19 to 0.03) | <0.001 (0.003) | |
| 15 (n=3553) | −0.29 (−0.46 to −0.13) | −0.11 (−0.20 to −0.01) | 0.06 (−0.02 to 0.14) | −0.05 (−0.16 to 0.06) | <0.001 (0.008) | |
| 26 (n=3115) | −0.33 (−0.51 to −0.16) | −0.08 (−0.19 to 0.02) | 0.03 (−0.06 to 0.11) | −0.08 (−0.20 to 0.05) | 0.001 (0.124) | |
| 43: | ||||||
| Verbal memory (n=2522) | −0.17 (−0.37 to 0.02) | −0.08 (−0.20 to 0.03) | −0.07 (−0.17 to 0.02) | −0.17 (−0.31 to −0.04) | 0.079 (0.076) | |
| Search accuracy (n=2575) | −0.10 (−0.29 to 0.09) | −0.03 (−0.15 to 0.08) | −0.01 (−0.09 to 0.09) | 0.02 (−0.11 to 0.16) | 0.799 (0.901) | |
| Search speed (n=2574) | −0.03 (−0.22 to 0.16) | −0.05 (−0.17 to 0.06) | −0.05 (−0.14 to 0.04) | −0.07 (−0.21 to 0.07) | 0.776 (0.620) | |