Table 4. Cox regression analysis of paternal social class and survival from childhood leukaemia, adjusted for sex, age group, calendar time period and white blood cell count.

Social class	Hazard ratio (95% CI)	P-value
All leukaemias		<0.0001
I/II	1.00
IIIN/M	1.66 (1.20–2.29)
IV/V	1.96 (1.35–2.86)
Acute lymphoblastic leukaemia		<0.0001
I/II	1.00
IIIN/M	1.68 (1.20–2.36)
IV/V	1.86 (1.24–2.77)

Abbreviation: CI=confidence interval.