Table 2

Standardised mortality ratios (SMRs) by period from starting employment and by year of death, study of United Kingdom electricity generation and transmission workers, 1973–97

		Brain cancer^2-151				All causes
		Obs	Exp			SMR (95% CI)	Obs	Exp	SMR (95% CI)
Period from starting employment (y):
0–9	10	14.6	68 (33 to 126)		829	1133.1	73^2-165 (68 to 78)
10–19	57	42.6	134^2-150 (101 to 173)		3326	4024.7	83^2-165 (80 to 85)
20–29	42	47.1	89 (64 to 121)		4864	5688.9	86^2-165 (83 to 88)
⩾30	49	42.1	116 (86 to 154)		5826	7071.8	82^2-165 (80 to 85)
p Value for trend^2-152	p=0.74			p=0.09
Year of death:
1973–80	28	24.7	113 (75 to 164)		1947	2467.3	79^2-165 (75 to 82)
1981–1985	31	29.8	104 (71 to 148)		2794	3301.6	85^2-165 (82 to 88)
1986–1990	35	37.2	94 (66 to 131)		3617	4312.5	84^2-165 (81 to 87)
1991–1997	64	54.7	117 (90 to 149)		6487	7837.0	83^2-165 (81 to 85)
p Value for trend^2-152	p=0.81			p=0.32
Total	158	146.4	108 (92 to 126)		14845	17918.4	83^2-165 (82 to 84)

↵2-150 p<0.05;
↵2-165 p<0.001.
↵2-151 ICD-9 codes 191–192.
↵2-152 Four categories scored 1–4.