Ambient Air Pollution and Adult Asthma Incidence
Background Short-term exposure to air pollution has adverse effects among patients with asthma, but whether long-term exposure to air pollution is a cause of adult-onset asthma is unclear.
Objective We aimed to investigate the association between air pollution and adult onset asthma.
Methods Asthma incidence was prospectively assessed in six European cohorts. Exposures studied were annual average concentrations at home addresses for nitrogen oxides assessed for 23,704 participants (including 1,257 incident cases) and particulate matter (PM) assessed for 17,909 participants through ESCAPE land-use regression models and traffic exposure indicators. Meta-analyses of cohort-specific logistic regression on asthma incidence were performed. Models were adjusted for age, sex, overweight, education, and smoking and included city/area within each cohort as a random effect.
Results In this longitudinal analysis, asthma incidence was positively, but not significantly, associated with all exposure metrics, except for PMcoarse. Positive associations of borderline significance were observed for nitrogen dioxide [adjusted odds ratio (OR) = 1.10; 95% CI: 0.99, 1.21 per 10 μg/m; p = 0.10] and nitrogen oxides (adjusted OR = 1.04; 95% CI: 0.99, 1.08 per 20 μg/m; p = 0.08). Nonsignificant positive associations were estimated for PM10 (adjusted OR = 1.04; 95% CI: 0.88, 1.23 per 10 μg/m), PM2.5 (adjusted OR = 1.04; 95% CI: 0.88, 1.23 per 5 μg/m), PM2.5absorbance (adjusted OR = 1.06; 95% CI: 0.95, 1.19 per 10/m), traffic load (adjusted OR = 1.10; 95% CI: 0.93, 1.30 per 4 million vehicles × meters/day on major roads in a 100-m buffer), and traffic intensity (adjusted OR = 1.10; 95% CI: 0.93, 1.30 per 5,000 vehicles/day on the nearest road). A nonsignificant negative association was estimated for PMcoarse (adjusted OR = 0.98; 95% CI: 0.87, 1.14 per 5 μg/m).
Conclusions Results suggest a deleterious effect of ambient air pollution on asthma incidence in adults. Further research with improved personal-level exposure assessment (vs. residential exposure assessment only) and phenotypic characterization is needed.
Asthma has a high prevalence of 5–10% (Eder et al. 2006), and in 2010 ranked as the 28th leading cause of disability-adjusted life years worldwide (Murray et al. 2012). Asthma is a heterogeneous disease that may appear at any age (most often in childhood), and can persist, possibly remit, or show variable activity over time (Strachan et al. 1996; Wenzel 2012). The complexity of this chronic disease is particularly challenging, and more research is needed on the environmental determinants of the disease (and not only on the acute triggers of attacks), because the increase in asthma incidence over the last decades (Eder et al. 2006) strongly suggests a role of environmental factors. The role of air pollutants in triggering asthma exacerbations in young and adult asthma patients is established (Peel et al. 2005; Sunyer et al. 1997). Several studies support the role of air pollution in the development of asthma in childhood (Anderson et al. 2013; McConnell et al. 2010), but not all (Mölter et al. 2015). The role of air pollution in adult-onset asthma (i.e., asthma incidence) has been investigated in only a few studies (Anderson et al. 2013; Jacquemin et al. 2012; Young et al. 2014) and should not be extrapolated from studies in children because childhood-onset and adult-onset asthma are two distinct asthma phenotypes that have, at least partly, different clinical, biological, and genetic characteristics (Wenzel 2012). Among studies in adults, only four have used individually assigned air pollution estimates at home addresses. A small Swedish case–control study (203 cases and 203 controls) suggested an association of traffic-related nitrogen dioxide (NO2) with asthma incidence, but the study lacked statistical power (Modig et al. 2006). Both the Respiratory Health in Northern Europe (RHINE) study (3,824 participants) (Modig et al. 2009) and the European Community Respiratory Health Survey (ECRHS) (4,185 participants) (Jacquemin et al. 2009b) reported a positive association between NO2 and asthma incidence. The Swiss Study on Air Pollution and Health in Adults (SAPALDIA) found similar results, but only in never-smokers and using source-specific models of local traffic-related particulate matter (PM) as a marker of exposure (Künzli et al. 2009). A recent U.S. study suggested an association of PM2.5 (≤ 2.5 μm) with incident asthma in women (Young et al. 2014). Two recent reviews concluded that the existing evidence suggests a possible role of air pollution in adult-onset asthma but that the evidence is not conclusive because the studies lacked of power, suggesting the need for larger cohorts (Anderson et al. 2013; Jacquemin et al. 2012).
The European Study of Cohorts for Air Pollution Effects (ESCAPE) developed, for the first time at large scale, fully standardized air pollution measurement, modeling, and assignment methods to individually characterize home outdoor exposure (Beelen et al. 2013; Eeftens et al. 2012). We took advantage of a follow-up of > 10 years among 23,704 adults in six prospective cohorts from eight countries to assess the association between long-term exposure to ambient air pollution and asthma incidence in adulthood.
Abstract and Introduction
Abstract
Background Short-term exposure to air pollution has adverse effects among patients with asthma, but whether long-term exposure to air pollution is a cause of adult-onset asthma is unclear.
Objective We aimed to investigate the association between air pollution and adult onset asthma.
Methods Asthma incidence was prospectively assessed in six European cohorts. Exposures studied were annual average concentrations at home addresses for nitrogen oxides assessed for 23,704 participants (including 1,257 incident cases) and particulate matter (PM) assessed for 17,909 participants through ESCAPE land-use regression models and traffic exposure indicators. Meta-analyses of cohort-specific logistic regression on asthma incidence were performed. Models were adjusted for age, sex, overweight, education, and smoking and included city/area within each cohort as a random effect.
Results In this longitudinal analysis, asthma incidence was positively, but not significantly, associated with all exposure metrics, except for PMcoarse. Positive associations of borderline significance were observed for nitrogen dioxide [adjusted odds ratio (OR) = 1.10; 95% CI: 0.99, 1.21 per 10 μg/m; p = 0.10] and nitrogen oxides (adjusted OR = 1.04; 95% CI: 0.99, 1.08 per 20 μg/m; p = 0.08). Nonsignificant positive associations were estimated for PM10 (adjusted OR = 1.04; 95% CI: 0.88, 1.23 per 10 μg/m), PM2.5 (adjusted OR = 1.04; 95% CI: 0.88, 1.23 per 5 μg/m), PM2.5absorbance (adjusted OR = 1.06; 95% CI: 0.95, 1.19 per 10/m), traffic load (adjusted OR = 1.10; 95% CI: 0.93, 1.30 per 4 million vehicles × meters/day on major roads in a 100-m buffer), and traffic intensity (adjusted OR = 1.10; 95% CI: 0.93, 1.30 per 5,000 vehicles/day on the nearest road). A nonsignificant negative association was estimated for PMcoarse (adjusted OR = 0.98; 95% CI: 0.87, 1.14 per 5 μg/m).
Conclusions Results suggest a deleterious effect of ambient air pollution on asthma incidence in adults. Further research with improved personal-level exposure assessment (vs. residential exposure assessment only) and phenotypic characterization is needed.
Introduction
Asthma has a high prevalence of 5–10% (Eder et al. 2006), and in 2010 ranked as the 28th leading cause of disability-adjusted life years worldwide (Murray et al. 2012). Asthma is a heterogeneous disease that may appear at any age (most often in childhood), and can persist, possibly remit, or show variable activity over time (Strachan et al. 1996; Wenzel 2012). The complexity of this chronic disease is particularly challenging, and more research is needed on the environmental determinants of the disease (and not only on the acute triggers of attacks), because the increase in asthma incidence over the last decades (Eder et al. 2006) strongly suggests a role of environmental factors. The role of air pollutants in triggering asthma exacerbations in young and adult asthma patients is established (Peel et al. 2005; Sunyer et al. 1997). Several studies support the role of air pollution in the development of asthma in childhood (Anderson et al. 2013; McConnell et al. 2010), but not all (Mölter et al. 2015). The role of air pollution in adult-onset asthma (i.e., asthma incidence) has been investigated in only a few studies (Anderson et al. 2013; Jacquemin et al. 2012; Young et al. 2014) and should not be extrapolated from studies in children because childhood-onset and adult-onset asthma are two distinct asthma phenotypes that have, at least partly, different clinical, biological, and genetic characteristics (Wenzel 2012). Among studies in adults, only four have used individually assigned air pollution estimates at home addresses. A small Swedish case–control study (203 cases and 203 controls) suggested an association of traffic-related nitrogen dioxide (NO2) with asthma incidence, but the study lacked statistical power (Modig et al. 2006). Both the Respiratory Health in Northern Europe (RHINE) study (3,824 participants) (Modig et al. 2009) and the European Community Respiratory Health Survey (ECRHS) (4,185 participants) (Jacquemin et al. 2009b) reported a positive association between NO2 and asthma incidence. The Swiss Study on Air Pollution and Health in Adults (SAPALDIA) found similar results, but only in never-smokers and using source-specific models of local traffic-related particulate matter (PM) as a marker of exposure (Künzli et al. 2009). A recent U.S. study suggested an association of PM2.5 (≤ 2.5 μm) with incident asthma in women (Young et al. 2014). Two recent reviews concluded that the existing evidence suggests a possible role of air pollution in adult-onset asthma but that the evidence is not conclusive because the studies lacked of power, suggesting the need for larger cohorts (Anderson et al. 2013; Jacquemin et al. 2012).
The European Study of Cohorts for Air Pollution Effects (ESCAPE) developed, for the first time at large scale, fully standardized air pollution measurement, modeling, and assignment methods to individually characterize home outdoor exposure (Beelen et al. 2013; Eeftens et al. 2012). We took advantage of a follow-up of > 10 years among 23,704 adults in six prospective cohorts from eight countries to assess the association between long-term exposure to ambient air pollution and asthma incidence in adulthood.
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