Table 4

Poisson regression analyses (incidence rate ratios, IRR) with 95% CIs, likelihood ratio test (LR-test) and Pearson's correlation coefficient (Corr_Pearson) of OLD as underlying or contributing cause of death 1951–2007, by log-transformed cumulative exposure to dust fractions and employment duration, among 1162 ever-smoking Norwegian long-term silicon carbide (SiC) industry workers employed 1913–2003

	All (N=1162), 55 cases, 30 474 person-years				<15 years of employment duration (N=1115), 32 cases, 18 906 person-years				≥15 years of total employment duration (N=599), 23 cases, 11 567 person-years
	IRR^*	95% CI	LR-test^†	Corr_Pearson	IRR^*	95% CI	LR-test^†	Corr_Pearson	IRR^*	95% CI	LR-test^†	Corr_Pearson
Fibre	1.3	0.9 to 2.0	–	–	1.0	0.6 to 1.9	–	–	2.4	1.1 to 5.4	–	–
Fibre adjusted for quartz	1.0	0.6 to 1.8	p=0.2	0.80	0.7	0.3 to 1.7	p=0.3	0.76	1.6	0.5 to 4.5	p=0.2	0.83
Fibre adjusted for cristobalite	1.0	0.6 to 1.7	p=0.1	0.69	0.8	0.4 to 1.9	p=0.5	0.69	1.3	0.5 to 3.3	p=0.03	0.67
Fibre adjusted for SiC	1.0	0.6 to 1.6	p=0.05	0.66	0.9	0.4 to 1.7	p=0.03	0.54	2.3	0.9 to 5.9	p=0.9	0.75
SiC particles	1.6	1.1 to 2.5	–	–	2.0	1.0 to 3.7	–	–	1.6	0.9 to 3.2	–	–
SiC adjusted for quartz	1.5	1.0 to 2.4	p=0.3	0.55	2.0	1.0 to 3.7	p=0.4	0.44	1.3	0.6 to 2.7	p=0.03	0.64
SiC adjusted for cristobalite	1.5	0.9 to 2.3	p=0.2	0.54	2.0	1.0 to 3.9	p=0.9	0.49	1.0	0.5 to 2.2	p=0.005	0.57
SiC adjusted for fibre	1.6	1.0 to 2.7	p=0.9	0.66	2.0	1.1 to 3.8	p=0.7	0.54	1.1	0.4 to 2.7	p=0.06	0.75
Quartz	1.5	1.0 to 2.3	–	–	1.3	0.7 to 2.5	–	–	2.7	1.2 to 5.9	–	–
Quartz adjusted for cristobalite	1.2	0.6 to 2.2	p=0.2	0.71	1.3	0.6 to 2.9	p=0.9	0.68	1.4	0.5 to 4.4	p=0.04	0.72
Quartz adjusted for fibre	1.5	0.8 to 2.9	p=1.0	0.80	1.6	0.7 to 3.8	p=0.5	0.76	2.0	0.7 to 5.9	p=0.4	0.83
Quartz adjusted for SiC	1.3	0.8 to 2.1	p=0.06	0.55	1.3	0.6 to 2.8	p=0.03	0.44	2.6	1.1 to 5.9	p=0.5	0.64
Cristobalite	1.4	1.0 to 2.0	–	–	1.1	0.8 to 1.7	–	–	2.5	1.4 to 4.3	–	–
Cristobalite adjusted for quartz	1.3	0.8 to 2.0	p=0.6	0.71	1.0	0.6 to 1.7	p=0.5	0.68	2.1	1.0 to 4.4	p=0.6	0.72
Cristobalite adjusted for fibre	1.4	0.9 to 2.2	p=1.0	0.69	1.2	0.7 to 2.1	p=0.7	0.69	2.2	1.1 to 4.5	p=0.6	0.67
Cristobalite adjusted for SiC	1.2	0.9 to 1.8	p=0.1	0.54	1.0	0.6 to 1.5	p=0.04	0.49	2.4	1.3 to 4.5	p=0.9	0.57

↵* Adjusted for age (</≥75 years) and period of diagnosis (</≥ 1 January 1990).
↵† LR-test: likelihood ratio test comparing the model containing one exposure factor with a model containing two exposure factors.