Table 3.

Hazard ratio (HR) estimates and 95% confidence intervals (CIs) for the association between ${\mathrm{PM}}_{2.5}$ and nonaccidental mortality, as well as for copollutants (${\mathrm{NO}}_2$, Ozone, oxidative potential), within the Canadian Health and Environment Cohorts (CanCHECs) from 1991, 1996, 2001, and pooled cohorts. Effect modification analyses by immigrant status, sex, and age, and multi-pollutant models are also provided.

Subgroup/model	Model form	1991 Cohort			1996 Cohort			2001 Cohort			Pooled resultsa
		HR	95% CI		HR	95% CI		HR	95% CI		HR	95% CI		p-Value
All subjects
—	DAGb	0.982	0.959	1.006	1.033	1.016	1.051	1.120	1.096	1.146	1.044	1.031	1.056	$<0.01$
—	Fullc	1.041	1.016	1.066	1.041	1.024	1.059	1.084	1.060	1.108	1.053	1.041	1.065	$<0.01$
Immigrant statusd
No	DAG	0.975	0.951	1.000	1.024	1.005	1.043	1.105	1.078	1.133	1.032	1.019	1.045	$<0.01$
No	Full	1.049	1.022	1.076	1.058	1.039	1.078	1.089	1.062	1.116	1.064	1.050	1.078	0.09
Yes	DAG	1.016	0.945	1.092	1.082	1.040	1.125	1.190	1.131	1.253	1.104	1.073	1.136	$<0.01$
Yes	Full	1.006	0.935	1.081	1.027	0.987	1.068	1.109	1.053	1.167	1.049	1.019	1.079	0.03
Sexd
Female	DAG	0.956	0.921	0.993	1.001	0.976	1.026	1.121	1.084	1.160	1.022	1.004	1.040	$<0.01$
Female	Full	1.009	0.972	1.048	1.008	0.983	1.034	1.093	1.056	1.130	1.031	1.013	1.050	$<0.01$
Male	DAG	0.993	0.963	1.024	1.055	1.032	1.078	1.116	1.083	1.150	1.055	1.039	1.071	$<0.01$
Male	Full	1.053	1.021	1.086	1.062	1.039	1.086	1.071	1.040	1.104	1.062	1.046	1.079	0.74
Age during follow-upd
$<65\mathrm{y}$	DAG	1.022	0.971	1.075	1.057	1.019	1.097	1.176	1.119	1.236	1.078	1.051	1.106	$<0.01$
$<65\mathrm{y}$	Full	1.079	1.026	1.136	1.095	1.056	1.136	1.165	1.108	1.225	1.109	1.081	1.137	0.07
65–74 y	DAG	0.984	0.939	1.031	1.079	1.044	1.116	1.176	1.122	1.232	1.077	1.052	1.103	$<0.01$
65–74 y	Full	1.069	1.020	1.120	1.092	1.057	1.130	1.130	1.078	1.184	1.096	1.070	1.122	0.25
$>75\mathrm{y}$	DAG	0.929	0.899	0.961	0.986	0.964	1.009	1.062	1.031	1.094	0.994	0.978	1.010	$<0.01$
$>75\mathrm{y}$	Full	0.972	0.940	1.005	0.985	0.963	1.008	1.031	1.001	1.062	0.995	0.979	1.011	0.02
Single pollutant
${\mathrm{NO}}_2$	DAG	1.009	1.004	1.015	0.997	0.993	1.001	1.003	0.998	1.008	1.002	0.999	1.004	$<0.01$
${\mathrm{NO}}_2$	Full	1.015	1.009	1.020	1.001	0.997	1.005	1.003	0.998	1.009	1.005	1.002	1.008	$<0.01$
${\mathrm{O}}_3$	DAG	1.016	1.006	1.027	1.035	1.029	1.041	1.041	1.034	1.049	1.034	1.030	1.038	$<0.01$
${\mathrm{O}}_3$	Full	1.044	1.033	1.055	1.076	1.069	1.082	1.081	1.073	1.088	1.073	1.068	1.077	$<0.01$
${\mathrm{O}}_{\mathrm{x}}$	DAG	1.030	1.018	1.043	1.037	1.029	1.044	1.049	1.040	1.058	1.040	1.035	1.045	0.03
${\mathrm{O}}_{\mathrm{x}}$	Full	1.068	1.056	1.081	1.086	1.078	1.093	1.094	1.085	1.103	1.086	1.080	1.091	$<0.01$
Two pollutant
Adjusted for ${\mathrm{NO}}_2$e
${\mathrm{PM}}_{2.5}$	DAG	0.966	0.942	0.991	1.038	1.02	1.057	1.115	1.089	1.142	1.040	1.028	1.053	$<0.01$
${\mathrm{NO}}_2$	DAG	1.010	1.004	1.015	0.997	0.993	1.001	1.003	0.998	1.009	1.002	0.999	1.005	$<0.01$
${\mathrm{PM}}_{2.5}$	Full	1.014	0.989	1.041	1.039	1.021	1.058	1.078	1.052	1.104	1.043	1.030	1.056	$<0.01$
${\mathrm{NO}}_2$	Full	1.015	1.010	1.021	1.001	0.997	1.006	1.004	0.998	1.009	1.006	1.003	1.009	$<0.01$
Adjusted for ${\mathrm{O}}_3$e
${\mathrm{PM}}_{2.5}$	DAG	0.969	0.944	0.994	0.996	0.978	1.014	1.073	1.048	1.098	1.011	0.998	1.024	$<0.01$
${\mathrm{O}}_3$	DAG	1.016	1.006	1.026	1.034	1.028	1.04	1.040	1.033	1.047	1.033	1.029	1.037	$<0.01$
${\mathrm{PM}}_{2.5}$	Full	1.003	0.978	1.029	0.963	0.946	0.981	0.996	0.973	1.020	0.982	0.970	0.994	0.01
${\mathrm{O}}_3$	Full	1.043	1.033	1.054	1.074	1.068	1.08	1.079	1.072	1.086	1.071	1.067	1.075	$<0.01$
Adjusted for ${\mathrm{O}}_{\mathrm{x}}$e
${\mathrm{PM}}_{2.5}$	DAG	0.950	0.925	0.977	0.988	0.97	1.007	1.056	1.031	1.083	0.998	0.985	1.011	$<0.01$
${\mathrm{O}}_{\mathrm{x}}$	DAG	1.028	1.017	1.039	1.034	1.027	1.04	1.045	1.037	1.053	1.037	1.032	1.041	0.03
${\mathrm{PM}}_{2.5}$	Full	0.967	0.941	0.994	0.941	0.923	0.959	0.970	0.946	0.994	0.955	0.943	0.968	0.10
${\mathrm{O}}_{\mathrm{x}}$	Full	1.062	1.051	1.074	1.078	1.071	1.085	1.086	1.077	1.094	1.078	1.073	1.083	$<0.01$

Note: —, no data; ${\mathrm{NO}}_2$, nitrogen dioxide; ${\mathrm{O}}_{\mathrm{x}}$, combined oxidant capacity of ${\mathrm{O}}_3$ and ${\mathrm{NO}}_2$; ${\mathrm{O}}_3$, ambient ozone; ${\mathrm{PM}}_{2.5}$, particulate matter with aerodynamic diameter $\le 2.5\mathrm{\mu }\mathrm{m}$.

^aTests for heterogeneity of hazard ratio among cohorts: *$p<0.05$, **$p<0.01$.

^bDirected acyclic graph (DAG) model is stratified by 5-y age groups by age at baseline, sex, and immigrant status and included the following geographic-based covariates: four Canadian Marginalization Index dimensions, urban form, CMA/CA size and airshed.

^cFull model is stratified by 5-y age groups by age at baseline, sex, and immigrant status and included the geographic based covariates: four Canadian Marginalization Index dimensions, urban form, CMA/CA size and airshed, and the subject-based covariates: marital status, education, income quintile, Indigenous status, visible minority status, employment status, and occupational class.

^dNote that the models by immigrant status are not stratified by immigrant status. The models by sex are not stratified by sex.

^e${\mathrm{PM}}_{2.5}$ always uses 10 units, copollutants use: ${\mathrm{O}}_3$, $10.20\text{\hspace{0.17em} ppb}$; ${\mathrm{NO}}_2$, $6.63\text{\hspace{0.17em} ppb}$; ${\mathrm{O}}_{\mathrm{x}}$, $8.05\text{\hspace{0.17em} ppb}$.