Neuropsychological abilities underpinning academic attainment in children born extremely preterm

Figures & data

Table 1. Sample characteristics

		Total extremely preterm sample (n = 200)	Extremely preterm sample with complete data (n = 152) ^b	Term-born controls with complete data (n = 120)	Extremely preterm vs. controls with complete data; p value ^c
Males, n (%)		100 (50.0)	71 (46.7)	54 (45.0)	Non-significant
Age in years, mean (SD)		11.83 (0.55)	11.96 (0.50)	11.84 (0.58)	Non-significant
Index of Multiple Deprivation decile, mean (SD)		5.21 (2.79)	5.08 (2.83)	5.27 (2.88)	Non-significant
Mental Processing Index score (IQ)		85.3 (18.9)	89.5 (14.7)	102.98 (11.9)	<.001
Severe neurodevelopmental disability^a		36 (18.0)	12 (7.9)	0
Gestational age (weeks), median (inter-quartile range), n (%)		25.71 (25.14, 26.43)	25.71 (25.14–26.73)	-
	23 weeks	15 (7.5)	10 (6.6)	-	-
	24 weeks	28 (14.0)	21 (13.8)
	25 weeks	69 (34.5)	56 (36.8)
	26 weeks	88 (44.0)	65 (42.8)
Moderate/severe Bronchopulmonary dysplasia^d		127 (63.5)	88 (57.9)
Treated Retinopathy of Prematurity		36 (18.0)	26 (17.1)
Surgery for necrotizing enterocolitis		17 (8.5)	11 (7.2)
Significant preterm brain injury^e		37 (18.6)	24 (15.8)

^adefined as: one or more of MPI score more than 3 SD below the mean of term-born controls (<67); Gross Motor Function Classification System/Manual Ability Classification System score ≥3; no useful hearing with aids; sees gross light/movement only or no useful vision.

^bOne child included with substituted reading composite score due to severe cognitive impairment, but otherwise complete neuropsychological data.

^cChi-squared for sex and T-tests for other variables.

^dReceiving supplemental oxygen at 36 weeks post menstrual age.

^eOne or more of hydrocephalus (ventricular index >4 mm above 97^th centile), unilateral or bilateral hemorrhagic parenchymal infarction, porencephalic cyst, cystic periventricular leukomalacia.

Table 2. Academic attainment and neuropsychological abilities in extremely preterm children and term-born controls

	N	Term-born controls Mean (SD)	N	Extremely preterm Mean (SD)	Difference in means (95% CI)	Z score Difference in means (95% CI)	Adjusted Z score Difference in means (95% CI)^a	P value
Academic attainment
WIAT-II Reading Composite	140	103.4 (10.6)	195	91.8 (20.6)	−11.7 (−15.1, −8.3)	−1.1 (−1.4, −0.8)	−1.1 (−1.4, −0.7)	<.001
Word Reading	143	104.8 (9.5)	186	97.9 (15.4)	−6.9 (−9.6, −4.2)	−0.7 (−1.0, −0.4)	−0.7 (−1.0, −0.4)	<.001
Reading Comprehension	141	104.4 (11.7)	180	97.1 (17.1)	− 7.3 (−10.4, −4.1)	0.6 (−0.9, −0.4)	−0.6 (−0.9, −0.3)	<.001
Pseudoword Decoding	141	103.1 (9.5)	185	96.4 (13.0)	−6.8 (−9.2, −4.3)	−0.7 (−1.0, −0.5)	0.7 (−0.9, −0.4)	<.001
WIAT-II Mathematics Composite	139	109.4 (15.7)	197	86.6 (26.5)	−22.8 (−27.3, −18.3)	−1.5 (−1.7, −1.2)	−1.4 (−1.8, −1.1)	<.001
Mathematics Reasoning	139	102.9 (12.3)	187	86.3 (20.4)	−16.7 (−20.3, −13.1)	−1.4 (−1.7, −1.1)	−1.3 (−1.7, −1.0)	<.001
Numerical Operations	143	113.9 (16.3)	189	93.3 (25.9)	−20.7 (−25.2, −16.1)	−1.3 (−1.6, −1.0)	−1.2 (−1.5, −0.9)	<.001
Working memory
WISC-V Working Memory Index	125	100.7 (13.4)	161	91.2 (18.0)	−9.5 (−13.2, −5.9)	−0.7 (−1.0, −0.4)	−0.7 (−0.9, −0.4)	<.001
Digit span backwards scaled score (verbal working memory)	138	9.5 (2.4)	168	8.2 (3.1)	−1.4 (−2.0, −0.8)	−0.6 (−0.8, −0.3)	−0.5 (−0.7, −0.2)	<.001
Picture span overall scaled score (visuospatial working memory)	125	11.0 (2.6)	164	9.2 (3.8)	−1.8 (−2.6, −1.1)	−0.7 (−1.0, −0.4)	−0.7 (−1.0, −0.4)	<.001
Visuospatial processing
NEPSY-II Arrows (visuospatial processing)	143	9.9 (3.0)	191	6.8 (4.0)	−3.2 (−3.9, −2.4)	−1.1 (−1.3, −0.8)	−1.1 (−1.4, −0.8)	<.001
Attention
NEPSY-II Response Set (attention)	143	10.0 (2.7)	180	8.3 (3.7)	− 1.7 (−2.5, −1.0)	−0.6 (−0.9, −0.4)	−0.6 (−0.9, −0.4)	<.001
Verbal processing speed
NEPSY-II Speeded Naming (processing speed)	143	10.4 (2.6)	189	8.7 (3.7)	−1.7 (−2.4, −1.0)	−0.6 (−0.9, −0.4)	−0.6 (−0.9, −0.3)	<.001

^aDifferences in means adjusted for sex and IMD. Due to missing IMD data the N for each group is slightly smaller than that reported for the means

All comparisons remained significant Bonferroni correction (p < .004).

Table 3. Proportion of extremely preterm children and term-born controls with low attainment in reading and mathematics

	Term-born controls	Extremely preterm	OR (95% CI) Extremely preterm compared to controls	Adjusted OR (95% CI) extremely preterm compared to controls^c
Reading, n	140	195
Average/low average attainment n (%)^a	138 (98.6)	163 (83.6)
Low attainment n (%)^b	2 (1.4)	32 (16.4)	13.6 (3.2 to 57.5)	13.3 (3.1, 56.6)
Mathematics, n	139	197
Average/low average attainment n (%)^a	138 (99.3)	138 (70.1)
Low attainment n (%)^b	1 (0.7)	59 (29.9)	59.0 (8.1 to 431.9)	57.9 (7.9, 424.7)

^aDefined as less than 2 SD below the control group mean (reading composite score >80, mathematics composite score >76).

^bDefined as greater than 2 SD below the control group mean (reading composite score ≤80, mathematics composite score ≤76).

^cOR adjusted for sex and Index of Multiple Deprivation.

Table 4. Mediation analysis

	Predictor	Partially standardized point estimate	Standard Error ^a	p	95% Confidence Interval of partially standardized point estimate ^a	R^2
Attainment in mathematics (N = 272), whole sample mean = 99.73, SD 21.64
Total effect (c) (X to Y)	Prematurity status	−0.79	0.11	<.001	(−1.00, −0.57)	.20
Direct effect (c’) (X to Y controlling for M^1, M^2, M^3, M^4, M^5)	Prematurity status	−0.37	0.08	.001	(−0.55, −0.18)	.52
Indirect effects
Total indirect effects		−0.42	0.07	Significant	(−0.56, −0.28)
Verbal working memory (a1b1)		−0.10	0.04	Significant	(−0.18, −0.04)
Visuospatial working memory (a2b2)		−0.06	0.03	Significant	(−0.13, −0.02)
Visuospatial processing (a3b3)		−0.15	0.04	Significant	(−0.24, −0.08)
Selective and sustained attention (a4b4)		−0.04	0.02	Significant	(−0.09, <-0.01)
Verbal processing speed (a5b5)		−0.06	0.03	Significant	(−0.12, −0.02)
Attainment in reading (N = 271)^b, whole sample mean = 99.57, SD 13.09
Total effect (c) (X to Y)	Prematurity status	−0.44	0.12	<.001	(−0.67, −0.20)	.09
Direct effect (c’) (X to Y controlling for M^1, M^2, M^3, M^4, M^5)	Prematurity status	−0.01	0.10	.94	(−0.21, −0.19)	.44
Indirect effects
Total indirect effects		−0.43	0.09	Significant	(−0.62, −0.27)
Verbal working memory (a1b1)		−0.10	0.04	Significant	(−0.18, −0.04)
Visuospatial working memory (a2b2)		−0.08	0.03	Significant	(−0.15, −0.02)
Visuospatial processing (a3b3)		−0.20	0.05	Significant	(−0.31, −0.11)
Selective and sustained attention (a4b4)		0.02	0.02	Non-significant	(−0.02, 0.07)
Verbal processing speed (a5b5)		−0.07	0.03	Significant	(−0.15, −0.02)

^aBootstrapped for indirect effects.

^bOne child excluded due to substituted reading composite score.

Figure 1. Regression coefficients between EP birth, neuropsychological skills and mathematics scores.

Figure 2. Regression coefficients between EP birth, neuropsychological skills and reading scores.

Data availability statement

Data are available subject to the EPICure Data Sharing Policy (www.epicure.ac.uk) and will be available as part of the RECAP preterm Cohort Platform (https://recap-preterm.eu).