Table 2. Lymphocytic leukaemias: age at first infection (see list in the text), by number of siblings.

Age at first infection (y)	ca/co	OR (CI)
Siblings 0 or 1
<4	8/94	1.0 (ref.)
4–8	28/223	1.5 (0.6–3.4)
>8	24/145	1.8 (0.7–4.4)
Siblings 2 or more
<4	15/94	1.0 (ref.)
4–8	47/473	0.6 (0.3–1.2)
>8	68/360	1.0 (0.6–1.9)

Ca/co=cases/controls. Odds ratios(ORs) are age- and gender-adjusted; 95% CI=confidence interval.