Exposure to ambient air pollution and the incidence of dementia: A population-based cohort study.

Chen H, Kwong JC, Copes R, Hystad P, van Donkelaar A, Tu K, Brook JR, Goldberg MS, Martin RV, Murray BJ, Wilton AS, Kopp A, Burnett RT.

Environ Int. 2017 Sep 13; 108: 271-277. https://doi.org/10.1016/j.envint.2017.08.020

Abstract

INTRODUCTION:

Emerging studies have implicated air pollution in the neurodegenerative processes. Less is known about the influence of air pollution, especially at the relatively low levels, on developing dementia. We conducted a population-based cohort study in Ontario, Canada, where the concentrations of pollutants are among the lowest in the world, to assess whether air pollution exposure is associated with incident dementia.

METHODS:

The study population comprised all Ontario residents who, on 1 April 2001, were 55-85years old, Canadian-born, and free of physician-diagnosed dementia (~2.1 million individuals). Follow-up extended until 2013. We used population-based health administrative databases with a validated algorithm to ascertain incident diagnosis of dementia as well as prevalent cases. Using satellite observations, land-use regression model, and an optimal interpolation method, we derived long-term average exposure to fine particulate matter (≤2.5μm in diameter) (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃), respectively at the subjects’ historical residences based on a population-based registry. We used multilevel spatial random-effects Cox proportional hazards models, adjusting for individual and contextual factors, such as diabetes, brain injury, and neighborhood income. We conducted various sensitivity analyses, such as lagging exposure up to 10years and considering a negative control outcome for which no (or weaker) association with air pollution is expected.

RESULTS:

We identified 257,816 incident cases of dementia in 2001-2013. We found a positive association between PM_2.5 and dementia incidence, with a hazard ratio (HR) of 1.04 (95% confidence interval (CI): 1.03-1.05) for every interquartile-range increase in exposure to PM_2.5. Similarly, NO₂ was associated with increased incidence of dementia (HR=1.10; 95% CI: 1.08-1.12). No association was found for O₃. These associations were robust to all sensitivity analyses examined. These estimates translate to 6.1% of dementia cases (or 15,813 cases) attributable to PM_2.5 and NO₂, based on the observed distribution of exposure relative to the lowest quartile in concentrations in this cohort.

DISCUSSION:

In this large cohort, exposure to air pollution, even at the relative low levels, was associated with higher dementia incidence.

Estimated Changes in Life Expectancy and Adult Mortality Resulting from Declining PM_2.5 Exposures in the Contiguous United States: 1980–2010

Neal Fann, Sun-Young Kim, Casey Olives, and Lianne Sheppard.

https://ehp.niehs.nih.gov/ehp507/

Environ Health Perspect. 2017; Vol 125, Issue 9.  https://doi.org/10.1289/EHP507

ABSTRACT

Background: PM_2.5 precursor emissions have declined over the course of several decades, following the implementation of local, state, and federal air quality policies. Estimating the corresponding change in population exposure and PM_2.5-attributable risk of death prior to the year 2000 is made difficult by the lack of PM_2.5 monitoring data.

Objectives: We used a new technique to estimate historical PM_2.5 concentrations, and estimated the effects of changes in PM_2.5 population exposures on mortality in adults (age ≥30 y), and on life expectancy at birth, in the contiguous United States during 1980–2010.

Methods: We estimated annual mean county-level PM_2.5 concentrations in 1980, 1990, 2000, and 2010 using universal kriging incorporating geographic variables. County-level death rates and national life tables for each year were obtained from the U.S. Census and Centers for Disease Control and Prevention. We used log-linear and nonlinear concentration–response coefficients from previous studies to estimate changes in the numbers of deaths and in life years and life expectancy at birth, attributable to changes in PM_2.5.

Results: Between 1980 and 2010, population-weighted PM_2.5 exposures fell by about half, and the estimated number of excess deaths declined by about a third. The States of California, Virginia, New Jersey, and Georgia had some of the largest estimated reductions in PM_2.5-attributable deaths. Relative to a counterfactual population with exposures held constant at 1980 levels, we estimated that people born in 2050 would experience an ∼1-y increase in life expectancy at birth, and that there would be a cumulative gain of 4.4 million life years among adults ≥30 y of age.

Conclusions: Our estimates suggest that declines in PM_2.5 exposures between 1980 and 2010 have benefitted public health.

Beyond the Normalized Difference Vegetation Index (NDVI): Developing a Natural Space Index for population-level health research.

Rugel EJ, Henderson SB, Carpiano RM, Brauer M.

Environ Res. 2017 Aug 29; 159:474-483. doi:  10.1016/j.envres.2017.08.033

Abstract

BACKGROUND:

Natural spaces can provide psychological benefits to individuals, but population-level epidemiologic studies have produced conflicting results. Refining current exposure-assessment methods is necessary to advance our understanding of population health and to guide the design of health-promoting urban forms.

OBJECTIVES:

The aim of this study was to develop a comprehensive Natural Space Index that robustly models potential exposure based on the presence, form, accessibility, and quality of multiple forms of greenspace (e.g., parks and street trees) and bluespace (e.g., oceans and lakes).

MATERIAL AND METHODS:

The index was developed for greater Vancouver, Canada. Greenness presence was derived from remote sensing (NDVI/EVI); forms were extracted from municipal and private databases; and accessibility was based on restrictions such as private ownership. Quality appraisals were conducted for 200 randomly sampled parks using the Public Open Space Desktop Appraisal Tool (POSDAT). Integrating these measures in GIS, exposure was assessed for 60,242 postal codes using 100- to 1,600-m buffers based on hypothesized pathways to mental health. A single index was then derived using principal component analysis (PCA).

RESULTS:

Comparing NDVI with alternate approaches for assessing natural space resulted in widely divergent results, with quintile rankings shifting for 22-88% of postal codes, depending on the measure. Overall park quality was fairly low (mean of 15 on a scale of 0-45), with no significant difference seen by neighborhood-level household income. The final PCA identified three main sets of variables, with the first two components explaining 68% of the total variance. The first component was dominated by the percentages of public and private greenspace and bluespace and public greenspace within 250m, while the second component was driven by lack of access to bluespace within 1 km.

CONCLUSIONS:

Many current approaches to modeling natural space may misclassify exposures and have limited specificity. The Natural Space Index represents a novel approach at a regional scale with application to urban planning and policy-making.

Associations of Pregnancy Outcomes and PM_2.5 in a National Canadian Study

Stieb DM, Chen L, Beckerman BS, Jerrett M, Crouse DL, Omariba DW, Peters PA, van Donkelaar A, Martin RV, Burnett RT, Gilbert NL, Tjepkema M, Liu S, Dugandzic  RM.

Environ Health Perspect. 2016 Feb;124(2):243-9. doi:  10.1289/ehp.1408995

ABSTRACT

Background

Numerous studies have examined associations between air pollution and pregnancy outcomes, but most have been restricted to urban populations living near monitors.

Objectives

We examined the association between pregnancy outcomes and fine particulate matter in a large national study including urban and rural areas.

Methods

Analyses were based on approximately 3 million singleton live births in Canada between 1999 and 2008. Exposures to PM_2.5(particles of median aerodynamic diameter ≤ 2.5 μm) were assigned by mapping the mother’s postal code to a monthly surface based on a national land use regression model that incorporated observations from fixed-site monitoring stations and satellite-derived estimates of PM_2.5. Generalized estimating equations were used to examine the association between PM_2.5 and preterm birth (gestational age < 37 weeks), term low birth weight (< 2,500 g), small for gestational age (SGA; < 10th percentile of birth weight for gestational age), and term birth weight, adjusting for individual covariates and neighborhood socioeconomic status (SES).

Results

In fully adjusted models, a 10-μg/m³ increase in PM_2.5 over the entire pregnancy was associated with SGA (odds ratio = 1.04; 95% CI 1.01, 1.07) and reduced term birth weight (–20.5 g; 95% CI –24.7, –16.4). Associations varied across subgroups based on maternal place of birth and period (1999–2003 vs. 2004–2008).

Conclusions

This study, based on approximately 3 million births across Canada and employing PM_2.5 estimates from a national spatiotemporal model, provides further evidence linking PM_2.5 and pregnancy outcomes.