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Although concentrations of ambient air pollution continue to decline in high-income regions, epidemiological studies document adverse health effects at levels below current standards in many countries. The Health Effects Institute (HEI) recently completed a comprehensive research initiative to investigate the health effects of long-term exposure to low levels of air pollution in the United States (U.S.), Canada, and Europe. We provide an overview and synthesis of the results of this initiative along with other key research, the strengths and limitations of the research, and remaining research needs. The three studies funded through the HEI initiative estimated the effects of long-term ambient exposure to fine particulate matter (PM 2.5 ), nitrogen dioxide, ozone, and other pollutants on a broad range of health outcomes, including cause-specific mortality and cardiovascular and respiratory morbidity. To ensure high quality research and comparability across studies, HEI worked actively with the study teams and engaged independent expert panels for project oversight and review. All three studies documented positive associations between mortality and exposure to PM 2.5 below the U.S. National Ambient Air Quality Standards and current and proposed European Union limit values. Furthermore, the studies observed nonthreshold linear (U.S.), or supra-linear (Canada and Europe) exposure-response functions for PM 2.5 and mortality. Heterogeneity was found in both the magnitude and shape of this association within and across studies. Strengths of the studies included the large populations (7-69 million), state-of-the-art exposure assessment methods, and thorough statistical analyses that applied novel methods. Future work is needed to better understand potential sources of heterogeneity in the findings across studies and regions. Other areas of future work include the changing and evolving nature of PM components and sources, including wildfires, and the role of indoor environments. This research initiative provided important new evidence of the adverse effects of long-term exposures to low levels of air pollution at and below current standards, suggesting that further reductions could yield larger benefits than previously anticipated.

Objectives: Urban greenness has been shown to confer many health benefits including reduced risks of chronic disease, depression, anxiety, and, in a limited number of studies, loneliness. In this first Canadian study on this topic, we investigated associations between residential surrounding greenness and loneliness and social isolation among older adults., Methods: This cross-sectional analysis of the Canadian Longitudinal Study on Aging included 26,811 urban participants between 45 and 86 years of age. The Normalized Difference Vegetation Index (NDVI), a measure of greenness, was assigned to participants' residential addresses using a buffer distance of 500 m. We evaluated associations between the NDVI and (i) self-reported loneliness using the Center for Epidemiological Studies Depression Scale, (ii) whether participants reported "feeling lonely living in the local area", and (iii) social isolation. Logistic regression models were used to characterize associations between greenness and loneliness/social isolation while adjusting for individual socio-economic and health behaviours., Results: Overall, 10.8% of participants perceived being lonely, while 6.5% reported "feeling lonely in their local area". Furthermore, 16.2% of participants were characterized as being socially isolated. In adjusted models, we observed no statistically significant difference (odds ratio (OR) = 0.99; 95% confidence interval (CI) 0.93-1.04) in self-reported loneliness in relation to an interquartile range (IQR) increase of NDVI (0.06). However, for the same change in greenness, there was a 15% (OR = 0.85; 95% CI 0.72-0.99) reduced risk for participants who strongly agreed with "feeling lonely living in the local area". For social isolation, for an IQR increase in the NDVI, we observed a 7% (OR = 0.93; 95% CI 0.88-0.97) reduction in prevalence., Conclusion: Our findings suggest that urban greenness plays a role in reducing loneliness and social isolation among Canadian urbanites., (© 2023. The Author(s).)

Objectives: This population-based observational study explores the associations between individual-level and neighbourhood-level indices of active living with inpatient mental healthcare use among adults with an underlying chronic cardiometabolic condition., Design and Setting: Data from the 2013-2014 Canadian Community Health Survey were linked longitudinally to hospital records from the 2013/2014‒2017/2018 Discharge Abstract Database and to a geocoded measure of active living environments (ALE). Relationships between individuals' leisure-time physical activity and neighbourhood ALE with risk of hospital admission for mental health disorders were assessed using multivariable Cox regressions., Participants: A national cohort was identified from the survey data of 24 960 respondents aged 35 years and above reporting having been diagnosed with diabetes, hypertension and/or heart disease., Outcome Measure: Potentially avoidable hospitalisation for a mood, anxiety or substance use disorder over a 5-year period., Results: More than half (52%) of adults aged 35 years and above with a cardiometabolic disease were physically inactive in their daily lives, and one-third (34%) resided in the least activity-friendly neighbourhoods. The rate of being hospitalised at least once for a comorbid mental disorder averaged 8.1 (95% CI: 7.0 to 9.3) per 1000 person-years of exposure. Individuals who were at least moderately active were half as likely to be hospitalised for a comorbid mental health problem compared with those who were inactive (HR: 0.50 (95% CI: 0.38 to 0.65)). No statistically discernible associations between neighbourhood ALE and hospitalisation risks were found after controlling for individuals' behaviours and characteristics, including in separate models stratified by age group and by sex., Conclusions: The evidence base to support prioritisation of interventions focusing on the built environment favouring mental health-promoting physical activity among higher-risk adults at the population level, independently of individual-level behaviours and characteristics, remains limited., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Most socio-epidemiological studies on diabetes incidence, prevalence, or hospitalization focus on individual-level risk factors. This population-based cohort study sought to advance understanding on the associations of contextual characteristics and risk of diabetes-related avoidable hospitalization (DRAH) among at-risk Canadians., Data and Methods: A national cohort was compiled from the 2013/2014 Canadian Community Health Survey, representing 5.1 million adults aged 35 years and older, reporting having been diagnosed with diabetes, hypertension, or heart disease. Their information was linked longitudinally to hospitalization data from the 2013/14 to 2017/18 Discharge Abstract Database as well as to measures of geographic variability from the Material and Social Deprivation Index and the Index of Remoteness. Cox regression models were used to examine associations between the contextual indices and first occurrence of a DRAH., Results: Residents in the most rural and remote communities were 50% more likely (hazard ratio (HR): 1.51, 95% confidence interval (95% CI): 1.26 to 1.80) to experience a DRAH than those in the most urbanized and accessible communities, and residents in the most socially deprived areas were significantly more likely (HR: 1.44, 95% CI: 1.26 to 1.65) to be hospitalized than those in the most socially privileged areas, controlling for individuals' sociodemographic characteristics and health behaviours. Neighbourhood material deprivation did not exercise a statistically significant influence on hospitalization risk after adjusting for the other residential characteristics., Interpretation: There is a clear and significant gradient in diabetes-related hospitalization risk among Canadians with an underlying cardiometabolic condition by degree of residential remoteness and of neighbourhood social deprivation, independently of individual characteristics and despite Canada's universal healthcare system.

Introduction: Mortality is associated with long-term exposure to fine particulate matter (particulate matter ≤2.5 μm in aerodynamic diameter; PM 2.5 ), although the magnitude and form of these associations remain poorly understood at lower concentrations. Knowledge gaps include the shape of concentration-response curves and the lowest levels of exposure at which increased risks are evident and the occurrence and extent of associations with specific causes of death. Here, we applied improved estimates of exposure to ambient PM 2.5 to national population-based cohorts in Canada, including a stacked cohort of 7.1 million people who responded to census year 1991, 1996, or 2001. The characterization of the shape of the concentration-response relationship for nonaccidental mortality and several specific causes of death at low levels of exposure was the focus of the Mortality-Air Pollution Associations in Low Exposure Environments (MAPLE) Phase 1 report. In the Phase 1 report we reported that associations between outdoor PM 2.5 concentrations and nonaccidental mortality were attenuated with the addition of ozone (O 3 ) or a measure of gaseous pollutant oxidant capacity (O x ), which was estimated from O 3 and nitrogen dioxide (NO 2 ) concentrations. This was motivated by our interests in understanding both the effects air pollutant mixtures may have on mortality and also the role of O 3 as a copollutant that shares common sources and precursor emissions with those of PM 2.5 . In this Phase 2 report, we further explore the sensitivity of these associations with O 3 and O x , evaluate sensitivity to other factors, such as regional variation, and present ambient PM 2.5 concentration-response relationships for specific causes of death., Methods: PM 2.5 concentrations were estimated at 1 km 2 spatial resolution across North America using remote sensing of aerosol optical depth (AOD) combined with chemical transport model (GEOS-Chem) simulations of the AOD:surface PM 2.5 mass concentration relationship, land use information, and ground monitoring. These estimates were informed and further refined with collocated measurements of PM 2.5 and AOD, including targeted measurements in areas of low PM 2.5 concentrations collected at five locations across Canada. Ground measurements of PM 2.5 and total suspended particulate matter (TSP) mass concentrations from 1981 to 1999 were used to backcast remote-sensing-based estimates over that same time period, resulting in modeled annual surfaces from 1981 to 2016., Annual exposures to PM 2.5 were then estimated for subjects in several national population-based Canadian cohorts using residential histories derived from annual postal code entries in income tax files. These cohorts included three census-based cohorts: the 1991 Canadian Census Health and Environment Cohort (CanCHEC; 2.5 million respondents), the 1996 CanCHEC (3 million respondents), the 2001 CanCHEC (3 million respondents), and a Stacked CanCHEC where duplicate records of respondents were excluded (Stacked CanCHEC; 7.1 million respondents). The Canadian Community Health Survey (CCHS) mortality cohort (mCCHS), derived from several pooled cycles of the CCHS (540,900 respondents), included additional individual information about health behaviors. Follow-up periods were completed to the end of 2016 for all cohorts. Cox proportional hazard ratios (HRs) were estimated for nonaccidental and other major causes of death using a 10-year moving average exposure and 1-year lag. All models were stratified by age, sex, immigrant status, and where appropriate, census year or survey cycle. Models were further adjusted for income adequacy quintile, visible minority status, Indigenous identity, educational attainment, labor-force status, marital status, occupation, and ecological covariates of community size, airshed, urban form, and four dimensions of the Canadian Marginalization Index (Can-Marg; instability, deprivation, dependency, and ethnic concentration). The mCCHS analyses were also adjusted for individual-level measures of smoking, alcohol consumption, fruit and vegetable consumption, body mass index (BMI), and exercise behavior., In addition to linear models, the shape of the concentration-response function was investigated using restricted cubic splines (RCS). The number of knots were selected by minimizing the Bayesian Information Criterion (BIC). Two additional models were used to examine the association between nonaccidental mortality and PM 2.5 . The first is the standard threshold model defined by a transformation of concentration equaling zero if the concentration was less than a specific threshold value and concentration minus the threshold value for concentrations above the threshold. The second additional model was an extension of the Shape Constrained Health Impact Function (SCHIF), the eSCHIF, which converts RCS predictions into functions potentially more suitable for use in health impact assessments. Given the RCS parameter estimates and their covariance matrix, 1,000 realizations of the RCS were simulated at concentrations from the minimum to the maximum concentration, by increments of 0.1 μg/m 3 . An eSCHIF was then fit to each of these RCS realizations. Thus, 1,000 eSCHIF predictions and uncertainty intervals were determined at each concentration within the total range., Sensitivity analyses were conducted to examine associations between PM 2.5 and mortality when in the presence of, or stratified by tertile of, O 3 or O x . Additionally, associations between PM 2.5 and mortality were assessed for sensitivity to lower concentration thresholds, where person-years below a threshold value were assigned the mean exposure within that group. We also examined the sensitivity of the shape of the nonaccidental mortality-PM 2.5 association to removal of person-years at or above 12 μg/m 3 (the current U.S. National Ambient Air Quality Standard) and 10 μg/m 3 (the current Canadian and former [2005] World Health Organization [WHO] guideline, and current WHO Interim Target-4). Finally, differences in the shapes of PM 2.5 -mortality associations were assessed across broad geographic regions (airsheds) within Canada., Results: The refined PM 2.5 exposure estimates demonstrated improved performance relative to estimates applied previously and in the MAPLE Phase 1 report, with slightly reduced errors, including at lower ranges of concentrations (e.g., for PM 2.5 <10 μg/m 3 )., Positive associations between outdoor PM 2.5 concentrations and nonaccidental mortality were consistently observed in all cohorts. In the Stacked CanCHEC analyses (1.3 million deaths), each 10-μg/m 3 increase in outdoor PM 2.5 concentration corresponded to an HR of 1.084 (95% confidence interval [CI]: 1.073 to 1.096) for nonaccidental mortality. For an interquartile range (IQR) increase in PM 2.5 mass concentration of 4.16 μg/m 3 and for a mean annual nonaccidental death rate of 92.8 per 10,000 persons (over the 1991-2016 period for cohort participants ages 25-90), this HR corresponds to an additional 31.62 deaths per 100,000 people, which is equivalent to an additional 7,848 deaths per year in Canada, based on the 2016 population. In RCS models, mean HR predictions increased from the minimum concentration of 2.5 μg/m 3 to 4.5 μg/m 3 , flattened from 4.5 μg/m 3 to 8.0 μg/m 3 , then increased for concentrations above 8.0 μg/m 3 . The threshold model results reflected this pattern with -2 log-likelihood values being equal at 2.5 μg/m 3 and 8.0 μg/m 3 . However, mean threshold model predictions monotonically increased over the concentration range with the lower 95% CI equal to one from 2.5 μg/m 3 to 8.0 μg/m 3 . The RCS model was a superior predictor compared with any of the threshold models, including the linear model., In the mCCHS cohort analyses inclusion of behavioral covariates did not substantially change the results for both linear and nonlinear models. We examined the sensitivity of the shape of the nonaccidental mortality-PM 2.5 association to removal of person-years at or above the current U.S. and Canadian standards of 12 μg/m 3 and 10 μg/m 3 , respectively. In the full cohort and in both restricted cohorts, a steep increase was observed from the minimum concentration of 2.5 μg/m 3 to 5 μg/m 3 . For the full cohort and the <12 μg/m 3 cohort the relationship flattened over the 5 to 9 μg/m 3 range and then increased above 9 μg/m 3 . A similar increase was observed for the <10 μg/m 3 cohort followed by a clear decline in the magnitude of predictions over the 5 to 9 μg/m 3 range and an increase above 9 μg/m 3 . Together these results suggest that a positive association exists for concentrations >9 μg/m 3 with indications of adverse effects on mortality at concentrations as low as 2.5 μg/m 3 ., Among the other causes of death examined, PM 2.5 exposures were consistently associated with an increased hazard of mortality due to ischemic heart disease, respiratory disease, cardiovascular disease, and diabetes across all cohorts. Associations were observed in the Stacked CanCHEC but not in all other cohorts for cerebrovascular disease, pneumonia, and chronic obstructive pulmonary disease (COPD) mortality. No significant associations were observed between mortality and exposure to PM 2.5 for heart failure, lung cancer, and kidney failure., In sensitivity analyses, the addition of O 3 and O x attenuated associations between PM 2.5 and mortality. When analyses were stratified by tertiles of copollutants, associations between PM 2.5 and mortality were only observed in the highest tertile of O 3 or O x . Across broad regions of Canada, linear HR estimates and the shape of the eSCHIF varied substantially, possibly reflecting underlying differences in air pollutant mixtures not characterized by PM 2.5 mass concentrations or the included gaseous pollutants. Sensitivity analyses to assess regional variation in population characteristics and access to healthcare indicated that the observed regional differences in concentration-mortality relationships, specifically the flattening of the concentration-mortality relationship over the 5 to 9 μg/m 3 range, was not likely related to variation in the makeup of the cohort or its access to healthcare, lending support to the potential role of spatially varying air pollutant mixtures not sufficiently characterized by PM 2.5 mass concentrations., Conclusions: In several large, national Canadian cohorts, including a cohort of 7.1 million unique census respondents, associations were observed between exposure to PM 2.5 with nonaccidental mortality and several specific causes of death. Associations with nonaccidental mortality were observed using the eSCHIF methodology at concentrations as low as 2.5 μg/m 3 , and there was no clear evidence in the observed data of a lower threshold, below which PM 2.5 was not associated with nonaccidental mortality., (© 2022 Health Effects Institute. All rights reserved.)

Objectives: Some studies suggest that residential surrounding greenness is associated with improved mental health. Few of these studies have focussed on middle-aged and older adults, explored the modifying effects of social determinants of health, or accounted for the extent to which individuals interact with their neighbourhood environments., Methods: We analysed cross-sectional data collected from 26,811 urban participants of the Canadian Longitudinal Study of Aging who were between 45 and 86 years of age. Participants provided details on socioeconomic characteristics, health behaviours, and their frequency of neighbourhood interactions. The Normalized Difference Vegetation Index (NDVI), a measure of greenness, was assigned to participants' residential addresses at a buffer distance of 500 m. Four self-reported measures of mental health were considered: The Center for Epidemiologic Studies Depression Scale (CES-D-10; short scale), past diagnosis of clinical depression, perceptions of mental health, and the Satisfaction with Life Scale (SWLS). Regression models were used to describe associations between greenness and these outcomes, and spline models were fit to characterize the exposure-response function between greenness and CES-D-10 scores. Stratified analyses evaluated whether associations varied by sociodemographic status., Results: In adjusted models, we observed a 5% (Odds Ratio (OR) = 0.95; 95% CI = 0.90, 0.99) reduced odds of depressive symptoms in relation to an interquartile range increase of NDVI (0.06) within a 500 m buffer of the participant's residence. Similarly, we found an inverse association with a self-reported clinical diagnosis of depression (OR = 0.97; 95% CI = 0.92-1.01). Increases in surrounding greenness were associated with improved perceptions of mental health, and the SWLS. Our spline analyses found that beneficial effects between greenness and the CES-D-10 were strongest among those of lower income., Conclusions: These findings suggest that residential greenness has mental health benefits, and that interventions to increase urban greenness can help reduce social inequalities in mental health., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Using a nationally representative cohort of Canadian adults, we assessed associations between neighbourhood walkability and cause-specific mortality and investigated whether they differed by socioeconomic status., Methods: The study population was drawn from the 2001 Canadian Census Health and Environment Cohort, which contains individual-level data from a random sample of 20% of Canadian households mandated to complete the long-form census. We included those aged ≥ 25 years at baseline who lived in urban and suburban areas. The national death registry was used to ascertain annual vital status. Linkages to annual income tax data provided place of residence. The Canadian Active Living Environments, a national index that summarizes walkability across Canadian neighbourhoods, was assigned to individuals' residential history. The Cox proportional hazards model was used to assess associations between walkability and cause-specific mortality., Results: A total of 1.8 million participants (52.5% female) accrued 27.3 million person-years and 265 710 deaths during the 15-year follow-up. The adjusted hazard ratio (HR) for living in a highly walkable neighbourhood relative to living in the least walkable neighbourhoods was associated with a 9% (HR: 0.91 [0.88, 0.95]) and 3% (HR: 0.97 [0.94, 0.99]) reduced risk of cardiovascular and all non-accidental mortality, respectively. The strongest benefits of walkability were found among individuals within the lowest education and household income categories, and who lived in the most deprived neighbourhoods. There were no significant associations (most [class 5] versus least [class 1] walkable HR: 0.84 [0.61-1.16]) seen for accidental traffic mortality., Conclusions: Canadian adults who live in walkable neighbourhoods have lower rates of cardiovascular and non-accidental mortality, with the greatest benefits seen in those from the lowest socioeconomic groups., (Crown Copyright © 2022. Published by Elsevier Ltd. All rights reserved.)

Background: Over the last decade, several studies have reported that residential proximity to vegetation, or 'greenness', is associated with improved birth outcomes, including for term birth weight (TBW), preterm birth (PTB), and small for gestational age (SGA). However, there remain several uncertainties about these possible benefits including the role of air pollution, and the extent to they are influenced socioeconomic status., Methods: We addressed these gaps using a national population-based study of 2.2 million singleton live births in Canadian metropolitan areas between 1999 and 2008. Exposures to greenness, fine particulate matter (PM 2.5 ), and nitrogen dioxide (NO 2 ) were assigned to infants using the postal code of their mother's residence at the time of birth. The Normalized Difference Vegetation Index (NDVI) was used to characterize greenness, while estimates of ambient PM 2.5 and NO 2 were estimated using remote sensing, and a national land-use regression surface, respectively. Multivariable regression analysis was performed to describe associations between residential greenness and the birth outcomes. Stratified analyses explored whether these associations were modified by neighbourhood measures of socioeconomic status., Results: Mothers who lived in greener areas had a lower risk of low TBW, PTB, and SGA babies. These associations persisted after adjustment for ambient NO 2 and PM 2.5. Specifically, in fully adjusted models, an interquartile range (IQR = 0.16) increase in the NDVI within a residential buffer of 250 m yielded odds ratios of 0.93 (95% confidence interval (CI): 0.92, 0.94), 0.94 (95% CI: 0.92, 0.95), and 0.94 (95% CI: 0.93, 0.95) for the outcomes of PTB, low TBW, and SGA, respectively. Similarly, an IQR increase in greenness was associated with a 16.3 g (95% CI: 15.3, 17.4) increase in TBW. We found inverse associations between greenness and the occurrence of adverse birth outcomes regardless of the socioeconomic status of the neighbourhood., Interpretation: Our findings support the hypothesis that residential greenness contributes to healthier pregnancies, that these associations are independent from exposure to air pollution. , and that proximity to greenness benefits all mothers regardless of socioeconomic status., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: It has been postulated that social and economic inequalities may shape the distributions of comorbid diabetes and mental illness. This observational cohort study using linked population-based administrative and geospatial datasets aimed to describe associations between neighbourhood socioenvironments and disorder-specific mental health service use among adults with diabetes in the province of New Brunswick, Canada., Results: A baseline cohort of 66,275 persons aged 19 and over living with diabetes was identified. One-quarter (26.3%) had used healthcare services for mood and anxiety disorders at least once during the six-year follow-up period 2012/2013-2017/2018. Based on Cox proportional hazards models, the risk of mental health service contacts was significantly higher among those residing in the most materially deprived neighbourhoods [HR: 1.07 (95% CI: 1.01-1.14)] compared to those in the least so, and those in areas characterized with the highest residential instability [HR: 1.13 (95% CI: 1.05-1.22)] compared to those in areas with the lowest instability. Among adults with incident diabetes (N = 4410), age and sex but not neighbourhood factors were related to differential help-seeking behaviours for mental health problems. These findings underscored the gap between theoretical postulations and population-based observations in delineating the syndemics of neighbourhood socioenvironments and mental health outcomes in populations with high diabetes prevalence., (© 2022. The Author(s).)

Background: Residential greenness has been associated with health benefits, such as lower risk of mortality, cardiovascular disease, obesity, adverse birth outcomes and asthma and better psychological health. However, the variation in greenness across socioeconomic and demographic characteristics in urban areas of Canada has not been well documented., Data and Methods: Respondents to the 2016 Census long-form questionnaire were assigned estimates of exposure to residential greenness based on the mean Normalized Difference Vegetation Index (NDVI) (from 2012 or the most recent year available) within a 500 m buffer around their home, based on postal code. Census weights were used to determine differences in average exposure to greenness according to selected demographic and socioeconomic characteristics., Results: Mean residential greenness among the 5.3 million census respondents in urban Canada was 0.44 units of the NDVI (standard deviation = 0.18 units). Greenness was lower among immigrants (particularly recent immigrants), some groups designated as visible minorities (particularly people of Filipino ancestry), lower-income households and tenants (i.e., NDVI values ranging from 0.40 to 0.43 units). Greenness values were highest among White non-immigrants and higher-income households (i.e., NDVI values ranging from 0.46 to 0.47 units)., Discussion: Given the potentially multifaceted role that greenness plays in health outcomes, the inequalities in residential greenness described here may contribute to producing or exacerbating existing health inequalities in the Canadian population.

Background: Residential proximity to greenness in urban areas has been shown to confer a number of health benefits, including improved mental health. We investigated whether greenness was associated with self-reported stress, distress, and mental health among adult participants of multiple cycles of a national Canadian health survey, and whether these associations varied by sex, age, income, and neighbourhood characteristics., Methods: Our study population included 397,900 participants of the Canadian Community Health Survey, 18 years of age or older, who lived in census metropolitan areas between 2000 and 2015. We used the Normalized Difference Vegetation Index (NDVI) to characterize participants' exposure to greenness within 250 m, 500 m, and 1 km buffers from a representative location of their postal code. Health outcomes included: self-reported perceptions of life stress, psychological distress, and self-rated mental health. We used multiple regression models, adjusted for relevant individual and neighbourhood-level variables to estimate associations (and 95% confidence intervals) between each outcome and exposure to greenness., Findings: In models with all participants, we observed 6% lower odds of poor self-rated mental health per increase in the interquartile range (i.e., 0.12) of NDVI within a 500 m buffer. Across the three outcomes, we found substantial heterogeneity in effect size across categories of sex, age, and community-level indicators of deprivation and urban form. For example, each incremental increase in greenness exposure was associated with a reduction of 0.61 (95% CI: 0.81 to -0.51) on the K10 psychological distress score among those living in the active core of cities, and with an increase of 0.07 (95% CI: 0.03-0.12) on this score among those living in the most suburban areas., Conclusions: Our results indicate that the potential benefits of residential greenness on mental health vary across personal and neighbourhood-level characteristics and are sensitive to how the outcome is measured. Additional research is needed to understand which features of greenness are most relevant to different sub-groups of the population to maximize these health benefits., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Individual and neighbourhood-scale socioeconomic characteristics modify associations between exposure to air pollution and mortality. The role of stress, which may integrate effects of social and environmental exposures on health, is unknown. We examined whether an individual's perspective on their own well-being, as assessed using self-rated measures of stress and health, modifies the pollutant-mortality relationship., Methods: The Canadian Community Health Survey (CCHS)-mortality cohort includes respondents from surveys administered between 2001 and 2012 linked to vital statistics and postal codes from 1981 until 2016. Annual fine particulate matter (PM 2.5 ), nitrogen dioxide (NO 2 ), and ozone (O 3 ) exposure estimates were attached to a sample of cohort members aged 30-89 years (n = 398,300 respondents/3,848,400 person-years). We examined whether self-rated stress, distress, mental health, and general health modified associations between long-term exposure to each pollutant (three-year moving average with one-year lag) and non-accidental mortality using Cox survival models, adjusted for individual- (i.e. socioeconomic and behavioural) and neighbourhood-scale covariates., Results: In fully-adjusted models, the relationship between exposure to pollutants and mortality was stronger among those with poor self-rated mental health, including a significant difference for NO 2 (hazard ratio (HR) = 1.15, 95% CI 1.06-1.25 per IQR) compared to those with very good/excellent mental health (HR = 1.05, 95% CI 1.01-1.08; Cochran's Q = 4.01; p < 0.05). Poor self-rated health was similarly associated with higher pollutant-associated HRs, but only in unadjusted models. Stress and distress did not modify pollutant-mortality associations., Conclusions: Poor self-rated mental and general health were associated with increased mortality attributed to exposure to ambient pollutants., (Crown Copyright © 2020. Published by Elsevier Inc. All rights reserved.)

Depression and other mood and anxiety disorders are recognized as common complications following cardiac events. Some studies report poorer cardiac outcomes among patients in socioeconomically marginalized neighbourhoods. This study aimed to describe associations between socioeconomic and built environment characteristics of neighbourhood environments and mental health service contacts following an acute myocardial infarction (AMI or heart attack) among adults in the province of New Brunswick, Canada. This province is characterized largely by residents in small towns and rural areas. A cohort of all adults aged 45 and over surviving AMI and without a recent record of mental disorders was identified by linking provincial medical-administrative datasets. Residential histories were tracked over time to assign neighbourhood measures of marginalization, local climate zones, and physical activity friendliness (i.e., walkability). Cox models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of healthcare use for mood and anxiety disorders over the period 2003/04-2015/16 by neighbourhood characteristics. The baseline cohort included 13,330 post-AMI patients, among whom 32.5% were found to have used healthcare services for a diagnosed mood or anxiety disorder at least once during the period of observation. Among men, an increased risk of mental health service use was found among those living in areas characterized by high ethnic concentration (HR: 1.14 (95%CI: 1.03-1.25)). Among women, the risk was significantly higher among those in materially deprived neighbourhoods (HR: 1.16 (95%CI: 1.01-1.33)). We found no convincing evidence of associations between this outcome and the other neighbourhood characteristics considered here. These results suggest that selected features of neighbourhood environments may increase the burden on the healthcare system for mental health comorbidities among adults with cardiovascular disease. Further research is needed to understand the differing needs of socioeconomically marginalized populations to improve mental health outcomes following an acute cardiac event, specifically in the context of smaller and rural communities and of universal healthcare coverage.

Background: Immigrants make up 20% of the Canadian population; however, little is known about the mortality impacts of fine particulate matter (PM 2.5 ) air pollution on immigrants compared with non-immigrants, or about how impacts may change with duration in Canada., Data and Methods: This study used the 2001 Canadian Census Health and Environment Cohort, a longitudinal cohort of 3.5 million individuals, of which 764,000 were classified as immigrants (foreign-born). Postal codes from annual income tax files were used to account for mobility among respondents and to assign annual PM 2.5 concentrations from 1998 to 2016. Exposures were estimated as a three-year moving average prior to the follow-up year. Cox survival models were used to determine hazard ratios (HRs) for cause-specific mortality, comparing the Canadian and foreign-born populations, with further stratification by year of immigration grouped into 10-year cohorts., Results: Differences in urban-rural settlement patterns resulted in greater exposure to PM 2.5 for immigrants compared with non-immigrants (mean = 9.3 vs. 7.5 μg/m 3 ), with higher exposures among more recent immigrants. In fully adjusted models, immigrants had higher HRs per 10 μg/m 3 increase in PM 2.5 concentration compared with Canadian-born individuals for cardiovascular mortality (HR [95% confidence interval] = 1.22 [1.12 to 1.34] vs. 1.12 [1.07 to 1.18]) and cerebrovascular mortality (HR = 1.25 [1.03 to 1.52] vs. 1.03 [0.93 to 1.15]), respectively. However, tests for differences between the two groups were not significant when Cochran's Q test was used. No significant associations were found for respiratory outcomes, except for lung cancer in non-immigrants (HR = 1.10 [1.02 to 1.18]). When stratified by year of immigration, differences in HRs across varied by cause of death., Discussion: In Canada, PM 2.5 is an equal-opportunity risk factor, with immigrants experiencing similar if not higher mortality risks compared with non-immigrants for cardiovascular-related causes of death. Some notable differences also existed with cerebrovascular and lung cancer deaths. Continued reductions in air pollution, particularly in urban areas, will improve the health of the Canadian population as a whole.

Background: The temporal and spatial scales of exposure assessment may influence observed associations between fine particulate air pollution (PM2.5) and mortality, but few studies have systematically examined this question., Methods: We followed 2.4 million adults in the 2001 Canadian Census Health and Environment Cohort for nonaccidental and cause-specific mortality between 2001 and 2011. We assigned PM2.5 exposures to residential locations using satellite-based estimates and compared three different temporal moving averages (1, 3, and 8 years) and three spatial scales (1, 5, and 10 km) of exposure assignment. In addition, we examined different spatial scales based on age, employment status, and urban/rural location, and adjustment for O3, NO2, or their combined oxidant capacity (Ox)., Results: In general, longer moving averages resulted in stronger associations between PM2.5 and mortality. For nonaccidental mortality, we observed a hazard ratio of 1.11 (95% CI = 1.08, 1.13) for the 1-year moving average compared with 1.23 (95% CI = 1.20, 1.27) for the 8-year moving average. Respiratory and lung cancer mortality were most sensitive to the spatial scale of exposure assessment with stronger associations observed at smaller spatial scales. Adjustment for oxidant gases attenuated associations between PM2.5 and cardiovascular mortality and strengthened associations with lung cancer. Despite these variations, PM2.5 was associated with increased mortality in nearly all of the models examined., Conclusions: These findings support a relationship between outdoor PM2.5 and mortality at low concentrations and highlight the importance of longer-exposure windows, more spatially resolved exposure metrics, and adjustment for oxidant gases in characterizing this relationship.

Background: Marked disparities by socioeconomic status in the risk of potentially avoidable hospitalization for chronic illnesses have been observed in many contexts, including those with universal health coverage. Less well known is how gender mediates such differences. We conducted a population-based cohort study to describe associations between household and community-level income and rehospitalizations for types 1 and 2 diabetes mellitus among Canadian women and men., Methods: Our cohorts were drawn from respondents to the 2006 mandatory long-form census linked longitudinally to 3 years of nationally standardized hospital records. We included adults 30-69 years hospitalized with diabetes at least once during the study period. We used logistic regressions to estimate odds ratios for 12-month diabetes rehospitalization associated with indicators of household and community-level income, with separate models by gender, and controlling for a range of other sociodemographic characteristics. Since diabetes may not always be recognized as the main reason for hospitalization, we accounted for disease progression through consideration of admissions where diabetes was previously identified as a secondary diagnosis., Results: Among persons hospitalized at least once with diabetes (n = 41,290), 1.5% were readmitted within 12 months where the initial admission had diabetes as the primary diagnosis, and 1.8% were readmitted where the initial admission had diabetes as a secondary diagnosis. For men, being in the lowest household income quintile was associated with higher odds of rehospitalization in cases where the initial admission listed diabetes as either the primary diagnosis (OR = 2.21; 95% CI = 1.38-3.51) or a secondary diagnosis (OR = 1.51; 95% CI = 1.02-2.24). For women, we found no association with income and rehospitalization, but having less than university education was associated with higher odds of rehospitalization where diabetes was a secondary diagnosis of the initial admission (OR = 1.88; 95% CI = 1.21-2.92). We also found positive, but insignificant associations between community-level poverty and odds of rehospitalization., Conclusions: Universal health coverage remains insufficient to eliminate socioeconomic inequalities in preventable diabetes-related hospitalizations, as illustrated in this Canadian context. Decision-makers should tread cautiously with gender-blind poverty reduction actions aiming to enhance population health that may inadequately respond to the different needs of disadvantaged women and men with chronic illness.

Background: Approximately 2.9 million deaths are attributed to ambient fine particle air pollution around the world each year (PM 2.5 ). In general, cohort studies of mortality and outdoor PM 2.5 concentrations have limited information on individuals exposed to low levels of PM 2.5 as well as covariates such as smoking behaviours, alcohol consumption, and diet which may confound relationships with mortality. This study provides an updated and extended analysis of the Canadian Community Health Survey-Mortality cohort: a population-based cohort with detailed PM 2.5 exposure data and information on a number of important individual-level behavioural risk factors. We also used this rich dataset to provide insight into the shape of the concentration-response curve for mortality at low levels of PM 2.5 ., Methods: Respondents to the Canadian Community Health Survey from 2000 to 2012 were linked by postal code history from 1981 to 2016 to high resolution PM 2.5 exposure estimates, and mortality incidence to 2016. Cox proportional hazard models were used to estimate the relationship between non-accidental mortality and ambient PM 2.5 concentrations (measured as a three-year average with a one-year lag) adjusted for socio-economic, behavioural, and time-varying contextual covariates., Results: In total, 50,700 deaths from non-accidental causes occurred in the cohort over the follow-up period. Annual average ambient PM 2.5 concentrations were low (i.e. 5.9 μg/m 3 , s.d. 2.0) and each 10 μg/m 3 increase in exposure was associated with an increase in non-accidental mortality (HR = 1.11; 95% CI 1.04-1.18). Adjustment for behavioural covariates did not materially change this relationship. We estimated a supra-linear concentration-response curve extending to concentrations below 2 μg/m 3 using a shape constrained health impact function. Mortality risks associated with exposure to PM 2.5 were increased for males, those under age 65, and non-immigrants. Hazard ratios for PM 2.5 and mortality were attenuated when gaseous pollutants were included in models., Conclusions: Outdoor PM 2.5 concentrations were associated with non-accidental mortality and adjusting for individual-level behavioural covariates did not materially change this relationship. The concentration-response curve was supra-linear with increased mortality risks extending to low outdoor PM 2.5 concentrations.

Background: Ambient fine particulate air pollution with aerodynamic diameter ≤ 2.5   μ m ( PM 2.5 ) is an important contributor to the global burden of disease. Information on the shape of the concentration-response relationship at low concentrations is critical for estimating this burden, setting air quality standards, and in benefits assessments., Objectives: We examined the concentration-response relationship between PM 2.5 and nonaccidental mortality in three Canadian Census Health and Environment Cohorts (CanCHECs) based on the 1991, 1996, and 2001 census cycles linked to mobility and mortality data., Methods: Census respondents were linked with death records through 2016, resulting in 8.5 million adults, 150 million years of follow-up, and 1.5 million deaths. Using annual mailing address, we assigned time-varying contextual variables and 3-y moving-average ambient PM 2.5 at a 1 × 1   km spatial resolution from 1988 to 2015. We ran Cox proportional hazards models for PM 2.5 adjusted for eight subject-level indicators of socioeconomic status, seven contextual covariates, ozone, nitrogen dioxide, and combined oxidative potential. We used three statistical methods to examine the shape of the concentration-response relationship between PM 2.5 and nonaccidental mortality., Results: The mean 3-y annual average estimate of PM 2.5 exposure ranged from 6.7 to 8.0   μ g / m 3 over the three cohorts. We estimated a hazard ratio (HR) of 1.053 [95% confidence interval (CI): 1.041, 1.065] per 10 - μ g / m 3 change in PM 2.5 after pooling the three cohort-specific hazard ratios, with some variation between cohorts (1.041 for the 1991 and 1996 cohorts and 1.084 for the 2001 cohort). We observed a supralinear association in all three cohorts. The lower bound of the 95% CIs exceeded unity for all concentrations in the 1991 cohort, for concentrations above 2   μ g / m 3 in the 1996 cohort, and above 5   μ g / m 3 in the 2001 cohort., Discussion: In a very large population-based cohort with up to 25 y of follow-up, PM 2.5 was associated with nonaccidental mortality at concentrations as low as 5   μ g / m 3 . https://doi.org/10.1289/EHP5204.

Background: Indirect adjustment via partitioned regression is a promising technique to control for unmeasured confounding in large epidemiological studies. The method uses a representative ancillary dataset to estimate the association between variables missing in a primary dataset with the complete set of variables of the ancillary dataset to produce an adjusted risk estimate for the variable in question. The objective of this paper is threefold: 1) evaluate the method for non-linear survival models, 2) formalize an empirical process to evaluate the suitability of the required ancillary matching dataset, and 3) test modifications to the method to incorporate time-varying exposure data, and proportional weighting of datasets., Methods: We used the association between fine particle air pollution (PM 2.5 ) with mortality in the 2001 Canadian Census Health and Environment Cohort (CanCHEC, N = 2.4 million, 10-years follow-up) as our primary dataset, and the 2001 cycle of the Canadian Community Health Survey (CCHS, N = 80,630) as the ancillary matching dataset that contained confounding risk factor information not available in CanCHEC (e.g., smoking). The main evaluation process used a gold-standard approach wherein two variables (education and income) available in both datasets were excluded, indirectly adjusted for, and compared to true models with education and income included to assess the amount of bias correction. An internal validation for objective 1 used only CanCHEC data, whereas an external validation for objective 2 replaced CanCHEC with the CCHS. The two proposed modifications were applied as part of the validation tests, as well as in a final indirect adjustment of four missing risk factor variables (smoking, alcohol use, diet, and exercise) in which adjustment direction and magnitude was compared to models using an equivalent longitudinal cohort with direct adjustment for the same variables., Results: At baseline (2001) both cohorts had very similar PM 2.5 distributions across population characteristics, although levels for CCHS participants were consistently 1.8-2.0 μg/m 3 lower. Applying sample-weighting largely corrected for this discrepancy. The internal validation tests showed minimal downward bias in PM 2.5 mortality hazard ratios of 0.4-0.6% using a static exposure, and 1.7-3% when a time-varying exposure was used. The external validation of the CCHS as the ancillary dataset showed slight upward bias of -0.7 to -1.1% and downward bias of 1.3-2.3% using the static and time-varying approaches respectively., Conclusions: The CCHS was found to be fairly well representative of CanCHEC and its use in Canada for indirect adjustment is warranted. Indirect adjustment methods can be used with survival models to correct hazard ratio point estimates and standard errors in models missing key covariates when a representative matching dataset is available. The results of this formal evaluation should encourage other cohorts to assess the suitability of ancillary datasets for the application of the indirect adjustment methodology to address potential residual confounding., (Crown Copyright © 2019. Published by Elsevier Inc. All rights reserved.)

Background: Epidemiological studies have consistently demonstrated that exposure to fine particulate matter (PM 2.5 ) is associated with increased risks of mortality. To a lesser extent, a series of studies suggest that living in greener areas is associated with reduced risks of mortality. Only a handful of studies have examined the interplay between PM 2.5 , greenness, and mortality., Methods: We investigated the role of residential greenness in modifying associations between long-term exposures to PM 2.5 and non-accidental and cardiovascular mortality in a national cohort of non-immigrant Canadian adults (i.e., the 2001 Canadian Census Health and Environment Cohort). Specifically, we examined associations between satellite-derived estimates of PM 2.5 exposure and mortality across quintiles of greenness measured within 500 m of individual's place of residence during 11 years of follow-up. We adjusted our survival models for many personal and contextual measures of socioeconomic position, and residential mobility data allowed us to characterize annual changes in exposures., Results: Our cohort included approximately 2.4 million individuals at baseline, 194,270 of whom died from non-accidental causes during follow-up. Adjustment for greenness attenuated the association between PM 2.5 and mortality (e.g., hazard ratios (HRs) and 95% confidence intervals (CIs) per interquartile range increase in PM 2.5 in models for non-accidental mortality decreased from 1.065 (95% CI: 1.056-1.075) to 1.041 (95% CI: 1.031-1.050)). The strength of observed associations between PM 2.5 and mortality decreased as greenness increased. This pattern persisted in models restricted to urban residents, in models that considered the combined oxidant capacity of ozone and nitrogen dioxide, and within neighbourhoods characterised by high or low deprivation. We found no increased risk of mortality associated with PM 2.5 among those living in the greenest areas. For example, the HR for cardiovascular mortality among individuals in the least green areas was 1.17 (95% CI: 1.12-1.23) compared to 1.01 (95% CI: 0.97-1.06) among those in the greenest areas., Conclusions: Studies that do not account for greenness may overstate the air pollution impacts on mortality. Residents in deprived neighbourhoods with high greenness benefitted by having more attenuated associations between PM 2.5 and mortality than those living in deprived areas with less greenness. The findings from this study extend our understanding of how living in greener areas may lead to improved health outcomes., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

There is evidence that local traffic density and living near major roads can adversely affect health outcomes. We aimed to assess the relationship between local road length, proximity to primary highways, and cause-specific mortality in the 1991 Canadian Census Health and Environment Cohort (CanCHEC). In this long-term study of 2.6 million people, based on completion of the long-form census in 1991 and followed until 2011, we used annual residential addresses to determine the total length of local roads within 200 m of postal code representative points and the postal code's distance to primary highways. The association between exposure to traffic and cause-specific non-accidental mortality was estimated using Cox proportional hazards models, adjusting for individual covariates and contextual factors, including census division-level proportion in high school, the percentage of recent immigrants, and neighborhood income. We performed sensitivity analyses, including adjustment for exposure to PM 2.5 , NO 2 , or O 3 , restricting to subjects in core urban areas, and spatial variation by climatic zone. The hazard ratio (HR) for all non-accidental mortality associated with an interquartile increase in length of local roads was 1.05 (95% CI 1.04, 1.05), while for an interquartile range increase in proximity to primary highways, the HR was 1.03 (95% CI 1.02, 1.04). HRs by traffic quartile increased with increasing lengths of local roads, as well as with closer proximity to primary highways, for all mortality causes. The associations were stronger within subjects' resident in urban core areas, attenuated by adjustment for PM 2.5 , and HRs showed limited spatial variation by climatic zone. In the CanCHEC cohort, exposure to higher road density and proximity to major traffic roads was associated with increased mortality risk from cerebrovascular and cardiovascular disease, ischemic heart disease, COPD, respiratory disease, and lung cancer, with unclear results for diabetes., (Crown Copyright © 2019. Published by Elsevier Ltd. All rights reserved.)

Background: Diabetes is infrequently coded as the primary cause of death but may contribute to cardiovascular disease (CVD) mortality in response to fine particulate matter (PM2.5) exposure. We analyzed all contributing causes of death to examine susceptibility of diabetics to CVD mortality from long-term exposure., Methods: We linked a subset of the 2001 Canadian Census Health and Environment Cohort (CanCHEC) with 10 years of follow-up to all causes of death listed on death certificates. We used survival models to examine the association between CVD deaths (n = 123,500) and exposure to PM2.5 among deaths that co-occurred with diabetes (n = 20,600) on the death certificate. More detailed information on behavioral covariates and diabetes status at baseline available in the Canadian Community Health Survey (CCHS)-mortality cohort (n = 12,400 CVD deaths, with 2,800 diabetes deaths) complemented the CanCHEC analysis., Results: Among CanCHEC subjects, comention of diabetes on the death certificate increased the magnitude of association between CVD mortality and PM2.5 (HR = 1.51 [1.39-1.65] per 10 μg/m) versus all CVD deaths (HR = 1.25 [1.21-1.29]) or CVD deaths without diabetes (HR = 1.20 [1.16-1.25]). Among CCHS subjects, diabetics who used insulin or medication (included as proxies for severity) had higher HR estimates for CVD deaths from PM2.5 (HR = 1.51 [1.08-2.12]) relative to the CVD death estimate for all respondents (HR = 1.31 [1.16-1.47])., Conclusions: Mention of diabetes on the death certificate resulted in higher magnitude associations between PM2.5 and CVD mortality, specifically among those who manage their diabetes with insulin or medication. Analyses restricted to the primary cause of death likely underestimate the role of diabetes in air pollution-related mortality. See video abstract at, http://links.lww.com/EDE/B408.

Background: Increasing evidence suggests that residential exposures to natural environments, such as green spaces, are associated with many health benefits. Only a single study has examined the potential link between living near water and mortality., Objective: We sought to examine whether residential proximity to large, natural water features (e.g., lakes, rivers, coasts, "blue space") was associated with cause-specific mortality., Methods: Our study is based on a population-based cohort of nonimmigrant adults living in the 30 largest Canadian cities [i.e., the 2001 Canadian Census Health and Environment Cohort) (CanCHEC)]. Subjects were drawn from the mandatory 2001 Statistics Canada long-form census, who were linked to the Canadian mortality database and to annual income-tax filings, through 2011. We estimated associations between living within of blue space and deaths from several common causes of death. We adjusted models for many personal and contextual covariates, as well as for exposures to residential greenness and ambient air pollution., Results: Our cohort included approximately 1.3 million subjects at baseline, 106,180 of whom died from nonaccidental causes during follow-up. We found significant, reduced risks of mortality in the range of 12-17% associated with living within of water in comparison with living farther away, among all causes of death examined, except with external/accidental causes. Protective effects were found to be higher among women and all older adults than among other subjects, and protective effects were found to be highest against deaths from stroke and respiratory-related causes., Conclusions: Our findings suggest that living near blue spaces in urban areas has important benefits to health, but further work is needed to better understand the drivers of this association. https://doi.org/10.1289/EHP3397.

Background: Few studies examining the associations between long-term exposure to ambient air pollution and mortality have considered multiple pollutants when assessing changes in exposure due to residential mobility during follow-up., Objective: We investigated associations between cause-specific mortality and ambient concentrations of fine particulate matter (≤ 2.5 μm; PM2.5), ozone (O3), and nitrogen dioxide (NO2) in a national cohort of about 2.5 million Canadians., Methods: We assigned estimates of annual concentrations of these pollutants to the residential postal codes of subjects for each year during 16 years of follow-up. Historical tax data allowed us to track subjects' residential postal code annually. We estimated hazard ratios (HRs) for each pollutant separately and adjusted for the other pollutants. We also estimated the product of the three HRs as a measure of the cumulative association with mortality for several causes of death for an increment of the mean minus the 5th percentile of each pollutant: 5.0 μg/m3 for PM2.5, 9.5 ppb for O3, and 8.1 ppb for NO2., Results: PM2.5, O3, and NO2 were associated with nonaccidental and cause-specific mortality in single-pollutant models. Exposure to PM2.5 alone was not sufficient to fully characterize the toxicity of the atmospheric mix or to fully explain the risk of mortality associated with exposure to ambient pollution. Assuming additive associations, the estimated HR for nonaccidental mortality corresponding to a change in exposure from the mean to the 5th percentile for all three pollutants together was 1.075 (95% CI: 1.067, 1.084). Accounting for residential mobility had only a limited impact on the association between mortality and PM2.5 and O3, but increased associations with NO2., Conclusions: In this large, national-level cohort, we found positive associations between several common causes of death and exposure to PM2.5, O3, and NO2., Citation: Crouse DL, Peters PA, Hystad P, Brook JR, van Donkelaar A, Martin RV, Villeneuve PJ, Jerrett M, Goldberg MS, Pope CA III, Brauer M, Brook RD, Robichaud A, Menard R, Burnett RT. 2015. Ambient PM2.5, O3, and NO2 exposures and associations with mortality over 16 years of follow-up in the Canadian Census Health and Environment Cohort (CanCHEC). Environ Health Perspect 123:1180-1186; http://dx.doi.org/10.1289/ehp.1409276.

Objective: Recent studies suggest that chronic exposure to air pollution can promote the development of diabetes. However, whether this relationship actually translates into an increased risk of mortality attributable to diabetes is uncertain., Research Design and Methods: We evaluated the association between long-term exposure to ambient fine particulate matter (PM2.5) and diabetes-related mortality in a prospective cohort analysis of 2.1 million adults from the 1991 Canadian census mortality follow-up study. Mortality information, including ∼5,200 deaths coded as diabetes being the underlying cause, was ascertained by linkage to the Canadian Mortality Database from 1991 to 2001. Subject-level estimates of long-term exposure to PM2.5 were derived from satellite observations. The hazard ratios (HRs) for diabetes-related mortality were related to PM2.5 and adjusted for individual-level and contextual variables using Cox proportional hazards survival models., Results: Mean PM2.5 exposure levels for the entire population were low (8.7 µg/m3; SD, 3.9 µg/m3; interquartile range, 6.2 µg/m3). In fully adjusted models, a 10-µg/m3 elevation in PM2.5 exposure was associated with an increase in risk for diabetes-related mortality (HR, 1.49; 95% CI, 1.37-1.62). The monotonic change in risk to the population persisted to PM2.5 concentration<5 µg/m3., Conclusions: Long-term exposure to PM2.5, even at low levels, is related to an increased risk of mortality attributable to diabetes. These findings have considerable public health importance given the billions of people exposed to air pollution and the worldwide growing epidemic of diabetes.

The 1991 Canadian Census Cohort is the largest population-based cohort in Canada (N=2,734,835). Prior to the creation of this Cohort, no national population-based Canadian cohort was available to examine mortality by socioeconomic indicators. The 1991 Canadian Census Cohort was created via the linkage of a sub-sample of respondents from the mandatory 1991 Canadian Census long-form to historical tax summary files, Canadian Mortality Database, Canadian Cancer Database, 1991 Health and Activity Limitation Survey and a sub-sample of the Longitudinal Worker File. Overall ascertainment of mortality and cancer is anticipated to be nearly complete and the Cohort is broadly representative of most groups in the Canadian population. The Cohort has been used to examine mortality outcomes by different indicators of socioeconomic status, occupational categories, ethnic groups, educational attainment, and for exposure to ambient air pollution. Results have shown that the estimated remaining years of life at age 25 differed substantially by income adequacy quintile, educational attainment, housing type and Aboriginal ancestry.

Background: Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM(2.5))]. This is the first national-level cohort study to investigate these risks in Canada., Objective: We investigated the association between long-term exposure to ambient PM(2.5) and cardiovascular mortality in nonimmigrant Canadian adults., Methods: We assigned estimates of exposure to ambient PM(2.5) derived from satellite observations to a cohort of 2.1 million Canadian adults who in 1991 were among the 20% of the population mandated to provide detailed census data. We identified deaths occurring between 1991 and 2001 through record linkage. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for available individual-level and contextual covariates using both standard Cox proportional survival models and nested, spatial random-effects survival models., Results: Using standard Cox models, we calculated HRs of 1.15 (95% CI: 1.13, 1.16) from nonaccidental causes and 1.31 (95% CI: 1.27, 1.35) from ischemic heart disease for each 10-μg/m(3) increase in concentrations of PM(2.5). Using spatial random-effects models controlling for the same variables, we calculated HRs of 1.10 (95% CI: 1.05, 1.15) and 1.30 (95% CI: 1.18, 1.43), respectively. We found similar associations between nonaccidental mortality and PM2.5 based on satellite-derived estimates and ground-based measurements in a subanalysis of subjects in 11 cities., Conclusions: In this large national cohort of nonimmigrant Canadians, mortality was associated with long-term exposure to PM(2.5). Associations were observed with exposures to PM(2.5) at concentrations that were predominantly lower (mean, 8.7 μg/m(3); interquartile range, 6.2 μg/m(3)) than those reported previously.