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2017 Conference

Abstract Number: 265 | ID: 2017-265

A Nationwide Case-Crossover Study on Air Pollution and Mortality in the Medicare Population

Qian Di(Department of Environmental Health, Harvard T.H. Chan School of Public Heath, United States, qiandi@mail.harvard.edu), Lingzhen Dai(Department of Environmental Health, Harvard T.H. Chan School of Public Heath,United States), Antonella Zanobetti(Department of Environmental Health, Harvard T.H. Chan School of Public Heath,United States), Yun Wang(Department of Biostatistics, Harvard T.H. Chan School of Public Heath, United States), Christine Choirat(Department of Biostatistics, Harvard T.H. Chan School of Public Heath, United States), Francesca Dominici(Department of Biostatistics, Harvard T.H. Chan School of Public Heath, United States), Joel D. Schwartz(Department of Environmental Health, Harvard T.H. Chan School of Public Heath, United States)
Background/Aim: Many time-series studies have established associations between short-term exposure to ambient fine particles (PM2.5) or ozone and increased mortality. However, those studies have generally been limited to large cities, and evidence for the associations below the current National Ambient Air Quality Standards (NAAQS) is limited. Also, many previous studies had inadequate power to identify susceptible sub-groups.We examined the association of acute exposure to ambient PM2.5 and ozone with mortality using the case-crossover approach, on a large nationwide sample consisting of all Medicare participants in the U.S.
Methods: We conducted national case-crossover analyses to estimate the effects of PM2.5 and ozone on over 22 million deaths of Medicare participants during 2000 to 2012. Daily PM2.5 and ozone levels were assessed by previously published and validated prediction models. Daily exposures were matched to every ZIP code. We used conditional logistical regression to examine the association between mortality and PM2.5 and ozone in two-pollutant models. Effect modification by age, race, sex, socio-economic status (SES), and population density was also examined. In addition, we estimated the dose-response curves for PM2.5 and ozone.
Results: We found that mortality increased by 1.04% [95% confidence interval (CI): 0.95%, 1.14%] and 0.51% (95% CI: 0.41%, 0.61%) for every 10 µg/m3 and 10 ppb increase in PM2.5 and ozone, respectively. Sub-group analyses showed that blacks, people with a low SES, elders and females had higher risk estimates associated with air pollution. We observed a dose-response curve that showed linearity at low doses and attenuated at higher doses for the relationship between mortality and both PM2.5 and ozone.
Conclusions: Exposures to PM2.5 and ozone were significantly associated with higher risk of mortality, even at levels below current U.S. standards. Disadvantaged groups are more susceptible to air pollution. Tighter air quality standards are needed to protect public health.