Modifiers of short-term effects of ozone on mortality in eastern Massachusetts - A case-crossover analysis at individual level

Ren Cizao, Melly Steve, Schwartz, Schwartz Joel

Description

Substantial epidemiological studies demonstrate associations between exposure to ambient ozone and mortality. A few studies simply examine the modification of this ozone effect by individual characteristics and socioeconomic status, but socioeconomic status was usually coded at the city level. Methods This study used a case-crossover design to examine whether impacts of ozone on mortality were modified by socioeconomic status coded at the tract or characteristics at an individual level in eastern Massachusetts, US for a period May-September, 1995-2002, with a total of 157,197 non-accident deaths aging 35 years or older. We used moving averages of maximal 8-hour concentrations of ozone monitored at 8 stationary stations as personal exposure. Results A 10 ppb increase in the four-day moving average of maximal 8-hour ozone was associated with 1.68% (95% confidence interval (CI): 0.51%, 2.87%), 1.96% (95% CI: -1.83%, 5.90%), 8.28% (95% CI: 0.66%, 16.48%), 0.44% (95% CI: -1.45%, 2.37%), -0.83% (95% CI: -2.94%, 1.32%), -1.09% (95% CI: -4.27%, 2.19%) and 6.5% (95% CI: 1.74%, 11.49%) changes in all natural deaths, respiratory disorders, diabetes, cardiovascular diseases, heart diseases, acute myocardial infarction and stroke, respectively. We did not find any evidence that the associations were significantly modified by socioeconomic status or individual characteristics although small differences of estimates across subpopulations were demonstrated. Conclusions Exposure to ozone was associated with specific cause mortality in Eastern Massachusetts during May-September, 1995-2002. There was no evidence that effects of ozone on mortality were significantly modified by socioeconomic status and individual characteristics.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2010
• Nombre de lectures: 3
• Langue: English

Extrait

Renet al.Environmental Health2010,9:3 http://www.ehjournal.net/content/9/1/3

R E S E A R C HOpen Access Modifiers of shortterm effects of ozone on mortality in eastern Massachusetts  A case crossover analysis at individual level * Cizao Ren , Steve Melly, Joel Schwartz

Abstract Background:Substantial epidemiological studies demonstrate associations between exposure to ambient ozone and mortality. A few studies simply examine the modification of this ozone effect by individual characteristics and socioeconomic status, but socioeconomic status was usually coded at the city level. Methods:This study used a casecrossover design to examine whether impacts of ozone on mortality were modified by socioeconomic status coded at the tract or characteristics at an individual level in eastern Massachusetts, US for a period MaySeptember, 19952002, with a total of 157,197 nonaccident deaths aging 35 years or older. We used moving averages of maximal 8hour concentrations of ozone monitored at 8 stationary stations as personal exposure. Results:A 10 ppb increase in the fourday moving average of maximal 8hour ozone was associated with 1.68% (95% confidence interval (CI): 0.51%, 2.87%), 1.96% (95% CI: 1.83%, 5.90%), 8.28% (95% CI: 0.66%, 16.48%), 0.44% (95% CI: 1.45%, 2.37%), 0.83% (95% CI: 2.94%, 1.32%), 1.09% (95% CI: 4.27%, 2.19%) and 6.5% (95% CI: 1.74%, 11.49%) changes in all natural deaths, respiratory disorders, diabetes, cardiovascular diseases, heart diseases, acute myocardial infarction and stroke, respectively. We did not find any evidence that the associations were significantly modified by socioeconomic status or individual characteristics although small differences of estimates across subpopulations were demonstrated. Conclusions:Exposure to ozone was associated with specific cause mortality in Eastern Massachusetts during May September, 19952002. There was no evidence that effects of ozone on mortality were significantly modified by socioeconomic status and individual characteristics.

Background Substantial epidemiological evidence demonstrates that ambient ozone is associated with daily deaths and hospi tal admissions [15]. These associations are generally consistent across studies or robust to adjustment for secular time trends, shortterm variation or weather conditions [6]. Recently, interest in epidemiological studies has grown in how socioeconomic status (SES), individual characteris tics (e.g., age, race and gender) and weather conditions modify associations of exposure to air pollution with mor tality and hospital admissions. This issue is important in

* Correspondence: [e-mail] Exposure, Epidemiology, and Risk Program, Department of Environmental Health, Harvard School of Public Health, Landmark Center, West, 4th floor, 401 Park Street, Boston, MA 02215, USA

air pollution studies because better knowledge of these modifiers will increase the power to detect risk in future studies and aid in the identification of potential mechan isms of pollutants [7]. Several studies have examined the variation of effects of particulate matter or ozone on health outcomes across temperature levels or seasons [813]. Recently, an increasing number of epidemiological studies have examined effect modifications of SES and individual characteristics on associations of particulate matter with health outcomes at population and individual levels [1420]. However, to date, little work has been direc ted toward identifying which subpopulations are more sus ceptible to deaths due to effects of ambient ozone [21]. Many studies have examined effect modification using stratified methods [12,19,20], which will decrease the sta tistical power and lack the ability to examine directly

© 2010 Ren et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.