Coarse particulate matter air pollution and hospital admissions for cardiovascular and respiratory diseases among Medicare patients

Abstract

Context: Health risks of fine particulate matter of 2.5 microm or less in aerodynamic diameter (PM2.5) have been studied extensively over the last decade. Evidence concerning the health risks of the coarse fraction of greater than 2.5 microm and 10 microm or less in aerodynamic diameter (PM10-2.5) is limited.

Objective: To estimate risk of hospital admissions for cardiovascular and respiratory diseases associated with PM10-2.5 exposure, controlling for PM2.5.

Design, setting, and participants: Using a database assembled for 108 US counties with daily cardiovascular and respiratory disease admission rates, temperature and dew-point temperature, and PM10-2.5 and PM2.5 concentrations were calculated with monitoring data as an exposure surrogate from January 1, 1999, through December 31, 2005. Admission rates were constructed from the Medicare National Claims History Files, for a study population of approximately 12 million Medicare enrollees living on average 9 miles (14.4 km) from collocated pairs of PM10 and PM2.5 monitors.

Main outcome measures: Daily counts of county-wide emergency hospital admissions for primary diagnoses of cardiovascular or respiratory disease.

Results: There were 3.7 million cardiovascular disease and 1.4 million respiratory disease admissions. A 10-microg/m3 increase in PM10-2.5 was associated with a 0.36% (95% posterior interval [PI], 0.05% to 0.68%) increase in cardiovascular disease admissions on the same day. However, when adjusted for PM2.5, the association was no longer statistically significant (0.25%; 95% PI, -0.11% to 0.60%). A 10-microg/m3 increase in PM10-2.5 was associated with a nonstatistically significant unadjusted 0.33% (95% PI, -0.21% to 0.86%) increase in respiratory disease admissions and with a 0.26% (95% PI, -0.32% to 0.84%) increase in respiratory disease admissions when adjusted for PM2.5. The unadjusted associations of PM2.5 with cardiovascular and respiratory disease admissions were 0.71% (95% PI, 0.45%-0.96%) for same-day exposure and 0.44% (95% PI, 0.06% to 0.82%) for exposure 2 days before hospital admission.

Conclusion: After adjustment for PM2.5, there were no statistically significant associations between coarse particulates and hospital admissions for cardiovascular and respiratory diseases.

Figure 1

US Counties With a General Population Larger Than 200 000 and With at Least 210 Daily Measurements of Collocated PM₁₀ and PM_2.5 Data Between 1999 and 2005 Measurements are for 108 counties. The vertical line divides the east and west regions. PM₁₀ indicates particulate matter is 10 µm or less in aerodynamic diameter; PM_2.5, particulate matter is 2.5 µm or less in aerodynamic diameter.

Figure 2

Percentage Change in Emergency Hospital Admissions Rate for Cardiovascular Diseases per a 10-µg/m³ Increase in Particulate Matter Estimates are on average across 108 counties. PM_2.5 indicates particulate matter is 2.5 µm or less in aerodynamic diameter; PM₁₀, particulate matter is 10 µm or less in aerodynamic diameter; PM_10-2.5, particulate matter is greater than 2.5 µm and 10 µm or less in aerodynamic diameter; RR, relative risk. Error bars indicate 95% posterior intervals.

Figure 3

Percentage Change in Emergency Hospital Admissions Rate for Respiratory Diseases per a 10-µg/m³ Increase in Particulate Matter Estimates are on average across 108 counties. Erro�r bars indicate 95% posterior intervals. RR indicates relative risk.

Figure 4

Percentage Change in Emergency Hospital Admissions Rate for Cardiovascular Diseases and Respiratory Disease per a 10-µg/m³ Increase in PM_10-2.5 Unadjusted for PM _2.5, on average across 77 counties in the eastern United States and 31 counties in the western United States. PM_10-2.5 indicates particulate matter is greater than 2.5 µm and 10 µm or less in aerodynamic diameter. Error bars indicate 95% posterior intervals.

Figure 5

County-Specific Log Relative Risks of Emergency Hospital Admissions for Cardiovascular Disease per 10-µg/m³ Increase in PM_10-2.5 at Lag 0 Unadjusted for PM_2.5 and plotted vs percentage of urbanicity. The curve was fit to the data using a 2-stage hierarchical model regression. The size of circles is proportional to the standard error of the estimated log relative risk. PM_10-2.5 indicates particulate matter is greater than 2.5 µm and 10 µm or less in aerodynamic diameter.

Figure 6

Percentage Change in Emergency Hospital Admissions Rate for Cardiovascular Diseases per a 10-µg/m³ Increase in PM_2.5 On average across 202 US counties (a subset of the 204 counties reported by Dominici et al) with a population larger than 200 000 for 1999–2005. Estimates reported by Dominici et al for both emergency and elective hospitalizations for 204 counties and for the period 1999–2002 are denoted by empty dots. COPD indicates chronic obstructive pulmonary disease; PM2.5, particulate matter is 2.5 µm or less in aerodynamic diameter. Error bars indicate 95% posterior intervals.