Table 3

Acute lymphatic leukaemia and exposure risk stratification throughout the study period

		0–4 Years				5–9 Years				10–14 Years				15–16 Years				Total		SMR		RR		95% CI
		Person years	O			E	Person years			O	E			Person years	O			E	Person years	SMR		RR		O	E	Obs	Exp	Lower	Upper
	Always high risk
Male	9 060	1	0.62		5 364	1	0.22		2 135	1	0.07		230	0	0.00		3	0.91	3.30	7.65	0.84	197.54
Female	8 252	1	0.63		4 993	0	0.13		2 304	0	0.04		294	0	0.01		1	0.81	1.23	^3-150	0.13	^3-150
Total	17 312	2	1.25		10 357	1	0.35		4 439	1	0.11		524	0	0.01		4	1.72	2.33	10.07	1.31	244.14
	Always normal risk
Male	52 858	7	3.64		32 199	2	1.32		14 100	1	0.44		1601	0	0.02		10	5.42	1.85	4.28	0.75	91.58
Female	48 900	5	3.72		29 921	0	0.76		13 207	0	0.22		1464	0	0.03		5	4.73	1.06	^3-150	0.52	^3-150
Total	101 758	12	7.36		62 120	2	2.08		27 307	1	0.66		3065	0	0.05		15	10.15	1.48	6.40	1.19	132.86
	Always low risk
Male	23 012	0	1.59		13 246	1	0.54		5 644	0	0.18		613	0	0.01		1	2.32	0.43	1
Female	21 152	0	1.61		12 220	0	0.31		4 964	0	0.08		556	0	0.01		0	2.01	0.00	1
Total	44 164	0	3.20		25 466	1	0.85		10 608	0	0.26		1169	0	0.02		1	4.33	0.23	1
	Normal + High risk
Male	61 918	8	4.27		37 563	3	1.54		16 235	2	0.51		1831	0	0.02		13	6.34	2.05	4.76	0.87	99.69
Female	57 152	6	4.34		34 914	0	0.88		15 511	0	0.25		1758	0	0.04		6	5.51	1.09	^3-150	0.56	^3-150
Total	119 070	14	8.61		72 477	3	2.42		31 746	2	0.76		3589	0	0.06		19	11.85	1.60	6.94	1.33	142.25

O: observed, E: expected, RR: interval estimation of relative risk, RR: 95% CI: 95% confidence limits of RR.
↵3-150 Values were not calculated as no cases occurred among women in the low risk group.