Table 3. Association of magnetic field exposure and outcome: Cox proportional hazards regression analyses.

	Event-free survival						Survival
Variable	No. of cases	No. faileda	HR	95% HR CIb		P c	No. of cases	No. failed	HR	95% HR CI		Pc
Univariate analysis	386	73				0.4	386	30				0.2
<0.1 μT	251	42	1.00				251	17	1.00
0.1–0.19 μT	95	22	1.47	0.88	2.46		95	8	1.27	0.55	2.93
0.2–0.29 μT	21	4	1.15	0.41	3.20		21	1	0.68	0.09	5.13
⩾0.3 μT	19	5	1.66	0.66	4.18		19	4	3.39	1.14	10.06
Multivariate analysis
B-precursord	361	70				0.5	361	28				0.06
NCI risk group			1.76	1.01	2.88				2.78	1.29	5.96
SES			0.98	0.52	1.83				1.61	0.68	3.82
<0.1 μT	235	41	1.00				235	16	1.00
0.1–0.19 μT	89	20	1.25	0.72	2.19		89	7	1.16	0.47	2.84
0.2–0.29 μT	19	4	1.32	0.47	3.71		19	1	0.85	0.11	6.40
⩾0.3 μT	18	5	1.92	0.75	4.90		18	4	4.53	1.49	13.76

^aFailure events defined as failure to attain complete response during induction therapy, leukaemia relapse, secondary cancer, or death.

^bHR=hazard ratio; CI=confidence interval.

^cTest of trend for time-weighted average magnetic field exposure level.

^dAdjusted for National Cancer Institute (NCI) risk group and socioeconomic status (SES).