Table 2.

Mean differences in intelligence, attention and executive function between children aged 5 years born at term (reference group) and children born preterm (Denmark 2003–2008 (n=1776))*

	Born at term ≥37 weeks (n=1728)	Late preterm birth 34 to <37 weeks (n=40)		Moderately or very preterm birth <34 weeks (n=8)
	Mean (SD)	Mean difference	95% CI	Mean difference	95% CI
Intelligence (WPPSI-R)
Full-scale IQ
Unadjusted	105.64 (12.86)	−2.09	−6.91 to 2.74	−9.22	−20.25 to 1.81
Adjusted†		−0.05	−4.62 to 4.53	−10.56	-19.37, to 1.75
Verbal IQ
Unadjusted	104.81 (10.80)	−1.73	−5.23 to 1.76	−7.11	−15.64 to 1.41
Adjusted		−0.40	−4.84 to 4.05	−7.41	−13.37, to 1.45
Performance IQ
Unadjusted	105.14 (16.22)	−2.00	−9.02 to 5.03	−9.51	−20.46 to 1.45
Adjusted		0.38	−5.39 to 6.15	−11.71	−21.89 to 1.52
Attention (TEACh-5)
Overall attention
Unadjusted	0.01 (1.00)	−0.21	−0.70 to 0.28	−0.10	−0.72 to 0.52
Adjusted		−0.16	−0.59 to 0.26	−0.25	−1.00 to 0.50
Sustained attention
Unadjusted	0.01 (1.00)	−0.39	−0.76, to 0.01	−0.09	−0.62 to 0.44
Adjusted		−0.23	−0.64 to 0.19	−0.16	−0.83 to 0.52
Selective attention
Unadjusted	0.00 (1.00)	0.09	−0.46 to 0.63	0.02	−0.41 to 0.45
Adjusted		0.06	−0.42 to 0.53	−0.19	−0.65 to 0.27
Executive function (BRIEF)‡
Parent version
Global Executive Composite
Unadjusted	49.97 (9.98)	1.44	−4.03 to 6.90	−0.39	−16.52 to 15.74
Adjusted		2.26	−2.01 to 6.53	−0.20	−14.27 to 13.87
Behavioural Regulation Index
Unadjusted	50.01 (9.98)	−0.35	−5.50 to 4.79	−1.18	−16.17 to 13.81
Adjusted		0.40	−3.97 to 4.76	−1.95	−14.87 to 10.97
Metacognition Index
Unadjusted	49.95 (9.98)	2.41	−3.10 to 7.92	0.13	−15.24 to 15.51
Adjusted		3.19	−1.11 to 7.49	0.90	−12.60 to 14.41
Teacher version
Global Executive Composite
Unadjusted	49.94 (10.03)	4.47	−0.77 to 9.70	5.47	2.57 to 8.36
Adjusted		3.99	−0.82 to 8.81	5.33	2.39 to 8.27
Behavioural Regulation Index
Unadjusted	49.95 (10.01)	4.42	−0.38 to 9.21	5.29	2.08 to 8.50
Adjusted		3.79	−0.89 to 8.48	4.24	−0.56 to 9.03
Metacognition Index
Unadjusted	49.95 (10.03)	4.09	−1.55 to 9.73	5.07	0.61 to 9.54
Adjusted		3.77	−1.32 to 8.85	5.46	1.97 to 8.95

*Overall number of participants. Due to complete-case analyses, for the adjusted analyses, the actual number of participants for each outcome was: full-scale IQ (n=1748 (missing data for one late preterm birth)), verbal IQ (n=1749 (missing data for one late preterm birth)), performance IQ (n=1749 (missing data for one late preterm birth)), overall attention (n=1493 (missing data for seven late preterm births)), sustained attention (n=1586 (missing data for four late preterm births)), selective attention (n=1612 (missing data for four late preterm births)), Global Executive Composite (parents, n=1748 (missing data for one late preterm birth); teachers, n=1525 (missing data for seven late preterm births and one very to moderate preterm birth)), Behavioural Regulation Index (parents, n=1748 (missing data for one late preterm birth); teachers, n=1530 (missing data for seven late preterm births and one very to moderate preterm birth)), Metacognition Index (parents, n=1748 (missing data for one late preterm birth); teachers, n=1525 (missing data for seven late preterm births and one very to moderate preterm birth)).

†All adjusted analyses adjusted for maternal age, maternal IQ, average alcohol consumption in pregnancy, smoking in pregnancy, parity, maternal marital status, parental educational level, child sex, testing psychologist and age at testing.

‡A higher BRIEF score indicates more executive function difficulties (opposite than the other outcome measures).

BRIEF, Behaviour Rating Inventory of Executive Function; CI, confidence interval; IQ, intelligence quotient; N, number; SD, standard deviation; TEACh-5, Test of Everyday Attention for Children at Five; WPPSI-R, Wechsler Preschool and Primary Scales of Intelligence-Revised.