Table 6. Association between childhood acute leukaemia and factors implicated in Greaves' hypothesis, according to age at diagnosis and ALL subtype.

	Age				ALL subtypea
	2–6 years		6–15 years		Common B-cell ALL		Other ALL
	ORb	95% CI	ORb	95% CI	ORb	95% CI	ORb	95% CI
⩾4 infections in the 1st year of life
Any infection	0.7	(0.5–1.0)	1.0	(0.6–1.6)	0.8	(0.6–1.1)	0.7	(0.4–1.1)
ENT	0.7	(0.5–1.0)	1.0	(0.6–1.6)	0.8	(0.6–1.1)	0.7	(0.4–1.2)
Digestive	0		0.5	(0.1–2.8)	0.1	(0.01–0.7)	0.3	(0.04–2.5)
Day-care
Yes vs no	0.8	(0.5–1.2)	0.7	(0.5–1.1)	0.8	(0.6–1.0)	0.5	(0.3–0.9)
Age at start of day-care (any type)
<3 months	0.6	(0.4–1.0)	0.7	(0.4–1.2)	0.6	(0.4–0.9)	0.4	(0.2–0.8)
3–6 months	0.9	(0.5–1.6)	0.8	(0.4–1.3)	0.8	(0.6–1.3)	0.5	(0.2–1.1)
>6 months	1.3	(0.7–2.4)	0.7	(0.4–1.6)	1.1	(0.7–1.8)	1.0	(0.5–2.1)
Never	1.0	Ref	1.0	Ref	1.0	Ref	1.0	Ref
Birth order
1	1.0	Ref	1.0	Ref	1.0	Ref	1.0	Ref
2	0.8	(0.6–1.3)	0.7	(0.4–1.1)	0.9	(0.6–1.2)	1.1	(0.6–1.8)
3	1.4	(0.8–2.4)	0.7	(0.4–1.3)	1.2	(0.8–1.9)	0.8	(0.4–1.7)
⩾4	1.5	(0.7–3.3)	2.4	(0.9–6.3)	2.0	(1.1–3.8)	2.3	(0.9–6.1)
Breast-feeding
Yes vs no	1.0	(0.7–1.5)	1.4	(0.9–2.0)	1.2	(0.9–1.5)	1.1	(0.7–1.8)
Breast-feeding duration
Never	1.0	Ref	1.0	Ref	1.0	Ref	1.0	Ref
<3 months	0.8	(0.5–1.3)	1.7	(1.0–2.9)	1.2	(0.8–1.7)	1.1	(0.6–1.9)
⩾3 months	1.4	(0.8–2.2)	1.0	(0.6–1.6)	1.2	(0.8–1.7)	1.3	(0.7–2.2)

^aAnalysis restricted to children older than 1 year.

^bORs adjusted for stratification variables: gender, age at diagnosis, region of residence at diagnosis.