Table 2.

Distribution of age, sex and socioeconomic characteristics by case/control status, children aged 1 to 14 years old, pooled analysis of 13 studies (1980–2013), Childhood Leukemia International Consortium

	ALL (n = 7847)		Controls (n = 11,667)		ORa	95% CI	P
	n	%	n	%
Histological typeb
B lineage ALL	5967	76
BCP ALL	5837	74
T lineage ALL	820	10
Mixed lineage ALL	19	0.2
Unspecified ALL	648	8
Missing	393	5
Child's age (years)							<0.0001
Mean (SD)	5.2 (3.5)		5.6 (3.6)
<2	648	8	1106	9	0.76	0.67, 0.85
2	1323	17	1660	14	1.00	Ref
3	1332	17	1699	15	0.98	0.89, 1.09
4	1030	13	1457	13	0.90	0.81, 1.01
5–6	1319	17	2011	17	0.86	0.77, 0.95
7–8	780	10	1278	11	0.81	0.72, 0.91
9–11	782	10	1266	11	0.80	0.71, 0.90
12–14	633	8	1190	10	0.69	0.61, 0.79
Child's sex							0.07
Girl	3414	44	5260	45	1.00	Ref
Boy	4433	56	6407	55	1.06	0.99, 1.12
Maternal age (years)							<0.0001
<25	2028	26	2505	22	1.20	1.11, 1.29
25–29	2638	34	4028	35	1.00	Ref
30–34	2147	27	3306	29	1.02	0.95, 1.10
≥35	1009	13	1684	14	0.98	0.89, 1.08
Missing	25		144
Maternal education (highest degree)							<0.0001
Did not complete secondary education	1873	24	2881	25	1.25	1.15, 1.36
Completed secondary education	3437	44	4725	41	1.00	Ref
Completed tertiary education	2508	32	3947	34	0.98	0.91, 1.05
Missing	29		114
Socioeconomic status							<0.0001
Low	1916	25	2340	21	1.20	1.11, 1.30
Medium	3261	42	4889	43	1.00	Ref
High	2529	33	4126	36	0.93	0.86, 1.00
No occupation or missing	141		312

ALL, acute lymphoblastic leukemia; BCP ALL, B‐cell precursor acute lymphoblastic leukemia; BRA_SAOP, State of Sao Paulo Childhood Acute Lymphoblastic Leukemia Study (Brazil); CI, confidence interval; CR_CRCLS, Costa Rican Childhood Leukemia Study (Costa Rica); OR, odds ratio.

^aOdds ratio and 95% confidence interval were estimated by unconditional logistic regression adjusted for child's age at reference date, child's sex, and study of origin.

^bData on ALL histological type were not available for BRA_SAOP (n = 152) and CR_CRCLS (n = 241).