Table 1.

Data Availability and Sample Characteristics.

	Whole Sample		Low Risk	High Risk
	N (London/ Washington)	Mean (SD; range)	Mean (SD; range)	Mean (SD; range)
12 month visit	182 (100/82)
Age at visit		13.03 (1.43; 11−18)	13.08 (1.41; 11−17)	12.98 (1.45; 11−18)
MSEL non-verbal AE		15.47 (1.98; 8.5−23)	16.03 (1.79; 16−24.5)	14.96 (2.01; 8.5−23)
MSEL verbal AE		12.51 (2.61; 7.5−22)	12.97 (2.33; 9−22)	12.08 (2.80; 7.5−22)
Peak alpha frequency (Hz)		7.45 (0.44; 6.35−8.88)	7.44 (0.47; 6.35−8.88)	7.46 (0.43; 6.61−8.87)
18 month visit	78 (0/78)
Age at visit		18.10 (0.52; 17−20)	18.10 (0.60; 17−20)	18.10 (0.45; 17−20)
MSEL non-verbal AE		19.53 (1.88; 15.5−24.5)	19.82 (1.75; 16−24.5)	19.23 (1.98; 15.5−24)
MSEL verbal AE		17.89 (3.78; 7.5−27)	18.14 (3.22; 10−24)	17.64 (4.28; 7.5−27)
24 month visit	138 (95/43)
Age at visit		24.04 (1.00; 21−28)	23.88 (0.66; 23−26)	24.13 (1.14; 21−28)
MSEL non-verbal AE		25.69 (3.45; 17.5−36.5)	26.80 (3.61; 18.5−36.5)	25.12 (3.23; 17.5−34)
MSEL verbal AE		25.86 (5.32; 11.5−39.5)	28.09 (4.20; 17−39.5)	24.70 (5.49; 11.5−34.5)
36 month visit	100 (100/0)
Age at visit		37.93 (3.02; 32−53)	38.23 (3.05; 25−51)	37.66 (2.99; 32−53)
MSEL non-verbal AE		41.07 (6.65; 21−59.5)	42.80 (5.06; 27.5−55.5)	39.46 (7.54; 21−59.5)
MSEL verbal AE		41.44 (8.39; 8.5−58.5)	44.11 (6.68; 31.5−58.5)	39.02 (9.08; 8.5−56.5)

AE = age equivalent, MSEL = Mullen Scales of Early Learning, SD = standard deviation.