Etiology of persistent mathematics difficulties from childhood to adolescence following very preterm birth

Figures & data

Table 1. Participant characteristics

		Term-born adolescents N = 95	Very preterm adolescents N = 127	p
Gestational age, weeks	Mean (SD)	-	28.74 (1.91)	-
<28 weeks	N (%)	-	31 (24%)	-
28–31 weeks	N (%)	-	96 (76%)	-
Birthweight, grams	Mean (SD)	-	1219 (330)	-
<1000 g	N (%)	-	39 (31%)	-
1000–1499	N (%)	-	57 (45%)	-
≥1500 g	N (%)	-	31 (24%)	-
Male sex	N (%)	48 (51%)	71 (56%)	0.427
IMD score^a	Mean (SD)	17.66 (16.09)	19.81 (15.87)	0.323
Low deprivation	N (%)	49 (52%)	57 (45%)	0.326
Mid deprivation	N (%)	26 (27%)	32 (25%)	-
High deprivation	N (%)	20 (21%)	38 (30%)	-
Age at assessment	Mean (SD)	13.70 (0.74)	13.87 (0.68)	0.076
School year at assessment		-	-	0.525
Year 7	N (%)	6 (6%)	4 (3%)	-
Year 8	N (%)	34 (36%)	41 (32%)	-
Year 9	N (%)	43 (45%)	60 (48%)	-
Year 10	N (%)	12 (13%)	22 (17%)	-

^aIMD: Index of Multiple Deprivation (Smith et al., 2015)

Table 2. Adolescents’ performance on achievement tests, domain general cognitive tests and specific mathematics tests

	Term-born adolescents		Very preterm adolescents
Measure	N	Mean (SD)	N	Mean (SD)	Difference in means (95% CI)	p	Cohen’s d
Mathematics achievement
WIAT-II Mathematics Composite^ST	95	107.46 (17.10)	127	96.51 (21.19)	−10.95 (−16.18 to −5.73)	<0.001*	0.56
General cognitive skills
Non-verbal IQ^ST	95	98.26 (18.10)	127	94.13 (17.84)	−4.13 (−8.93 to 0.67)	0.091	0.23
Working memory^Raw	92	16.36 (4.18)	125	14.60 (4.04)	−1.76 (−2.87 to −0.65)	0.002*	0.44
Speed of processing^cRT	95	23.68 (4.65)	125	25.24 (7.75)	1.56 (−0.21 to 3.33)	0.083	0.24
Visuospatial skills^SC	95	10.21 (3.00)	127	9.05 (3.24)	−1.16 (−2.00 to −0.32)	0.007*	0.37
Inhibition^SC	95	8.87 (3.42)	127	8.00 (3.70)	−0.87 (−1.83 to 0.08)	0.073	0.24
Specific mathematics skills
Non-symbolic magnitude comparison^%A	95	82.97 (7.99)	127	83.67 (7.01)	1.01 (−1.29 to 2.69)	0.491	0.09
Symbolic magnitude comparison^mRT	95	0.76 (0.18)	127	0.78 (0.21)	0.02 (−0.04 to 0.07)	0.578	0.00
Cross notation comparison^%A	95	74.99 (9.25)	127	72.94 (9.94)	−2.04 (−4.62 to 0.54)	0.120	0.21
Number line estimation^%A	95	96.08 (1.94)	127	94.98 (3.72)	−1.10 (−1.93 to −0.28)	0.009	0.36
Reading large numbers^%A	95	96.78 (7.57)	127	92.77 (10.87)	−4.01 (−6.58 to −1.45)	0.002*	0.42
Writing large numbers^%A	95	91.38 (10.83)	127	83.12 (17.75)	−8.26 (−12.32 to −4.20)	<0.001*	0.54
Counting skills^%A	95	81.84 (17.84)	127	71.56 (23.13)	−10.29 (−15.91 to −4.66)	<0.001*	0.49
Number fact knowledge^%A	95	77.43 (20.97)	127	67.52 (24.60)	−9.91 (−16.09 to −3.73)	0.002*	0.43
Mental arithmetic^mRT	95	7.49 (3.27)	124	8.93 (3.87)	1.45 (0.47 to 2.42)	0.004	0.39
Written arithmetic^%A	95	76.78 (18.77)	127	66.68 (23.91)	−10.09 (−15.94 to −4.25)	0.001*	0.46
Understanding of arithmetic concepts^%A	95	92.24 (10.33)	127	84.65 (16.52)	−7.59 (−11.39 to 3.79)	<0.001*	0.53
Algebra^%A	95	66.11 (19.39)	127	53.96 (25.45)	−12.14 (−18.31 to −5.98)	<0.001*	0.53
Geometry^%A	95	48.98 (15.00)	127	45.25 (14.37)	−3.73 (−7.65 to 0.18)	0.061	0.25

Note: ^ST Standard scores (Mean 100, SD 15). ^SC Scaled scores (Mean 10, SD 3). ^%A Percent accuracy score. ^Raw Raw composite score for verbal and visuospatial working memory (range 5.7–25.0). ^cRT Composite reaction time (seconds). ^mRT Median reaction time (seconds). 3 participants do not have a composite working memory score due to experimenter error in task administration. *Significant after correction for multiple comparisons: Mathematics achievement p < 0.05; general cognitive skills p < 0.01; specific mathematics skills p < 0.004.

Table 3. Multivariate analyses of covariance results for group differences in mathematics achievement and specific mathematics skills between 122 very preterm adolescents and 92 term-born adolescents controlling for working memory and visuospatial skills

Measure	df	F	p	Partial η2
Mathematics achievement	1, 210	5.70	0.018	0.026
Number line estimation	1, 210	0.86	0.354	0.004
Reading large numbers	1, 210	1.82	0.178	0.009
Writing large numbers	1, 210	5.67	0.018	0.026
Counting skills	1, 210	2.56	0.111	0.012
Number fact knowledge	1, 210	1.32	0.253	0.006
Mental arithmetic	1, 210	3.18	0.076	0.015
Written arithmetic	1, 210	3.25	0.073	0.015
Understanding of arithmetic concepts	1, 210	5.39	0.021	0.025
Algebra	1, 210	3.78	0.053	0.018

Table 4. Descriptive statistics for test results among 83 very preterm adolescents and 49 term-born adolescents assessed at both primary (age 8–10 years) and secondary (age 11–15 years) school

	Term-born adolescents						Very preterm adolescents
	Primary (8–10 years)			Secondary (12–14 years)			Primary (8–10 years)			Secondary (12–14 years)
	N	Mean	SD	N	Mean	SD	N	Mean	SD	N	Mean	SD
Mathematics achievement	49	107.86	18.34	49	110.51	18.60	83	93.07	19.86	83	95.47	21.33
Nonverbal IQ	49	109.90	14.70	49	100.41	17.23	83	100.35	17.24	83	93.80	17.87
Working memory	46	14.54	3.69	46	17.51	4.58	81	11.88	3.18	81	14.72	4.28
Processing speed	49	29.26	5.62	49	23.32	4.47	80	33.64	10.03	80	24.95	5.91
Visuospatial skills	49	10.94	2.72	49	10.78	3.07	82	8.91	3.53	82	8.98	3.43
Inhibition	49	10.04	3.18	49	9.39	3.26	83	8.54	3.54	83	7.90	3.76

Table 5. Differences in mathematics achievement and general cognitive skills between groups (very preterm [n = 83] vs. term-born [n = 49]) and age at assessment (primary vs. secondary school), and group by time interactions

	Group				Age at assessment				Group x age interaction
	df	F	p	Partial η2	df	F	p	Partial η2	df	F	p	Partial η2
Mathematics achievement	(1,130)	18.81	<0.001	0.126	(1,130)	6.65	0.011	0.049	(1,130)	0.02	0.896	<0.001
Nonverbal IQ	(1,130)	8.82	0.004	0.064	(1,130)	32.48	<0.001	0.200	(1,130)	1.09	0.299	0.008
Working memory	(1,125)	17.21	<0.001	0.121	(1,125)	92.43	<0.001	0.425	(1,125)	0.05	0.828	<0.001
Processing speed	(1,127)	6.53	0.012	0.049	(1,127)	164.19	<0.001	0.564	(1,127)	5.85	0.017	0.044
Visuospatial skills	(1,129)	14.31	<0.001	0.100	(1,129)	0.03	0.868	<0.001	(1,129)	0.133	0.716	0.001
Inhibition	(1,130)	7.70	0.006	0.056	(1,130)	3.84	0.052	0.029	(1,130)	<0.001	0.982	<0.001

Figure 1. Non-verbal IQ and mathematics achievement at primary (age 8–10 years) and secondary school (age 11–15 years) in very preterm (n = 83) and term-born adolescents (n = 49). Error bars represent standard error. IQ at primary school was assessed using Raven’s Colored Progressive Matrices, and at secondary school using Raven’s Standard Progressive Matrices. Mathematics achievement was assessed using the Wechsler Individual Achievement Test 2^nd Edition at both time points

Smith, T., Noble, M., Noble, S., Wright, G., McLennan, D., & Plunkett, E. (2015). The English Indices of Deprivation 2015. Research report. Department for Communities and Local Government.

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