Particulate air pollution and survival in a COPD cohort.
BACKGROUND
Several studies have shown cross-sectional associations between long term exposure to particulate air pollution and survival in general population or convenience cohorts. Less is known about susceptibility, or year to year changes in exposure. We investigated whether particles were associated with survival in a cohort of persons with COPD in 34 US cities, eliminating the usual cross-sectional exposure and treating PM10 as a within city time varying exposure.


METHODS
Using hospital discharge data, we constructed a cohort of persons discharged alive with chronic obstructive pulmonary disease using Medicare data between 1985 and 1999. 12-month averages of PM10 were merged to the individual annual follow up in each city. We applied Cox's proportional hazard regression model in each city, with adjustment for individual risk factors.


RESULTS
We found significant associations in the survival analyses for single year and multiple lag exposures, with a hazard ratio for mortality for an increase of 10 microg/m(3) PM10 over the previous 4 years of 1.22 (95% CI: 1.17-1.27).


CONCLUSIONS
Persons discharged alive for COPD have substantial mortality risks associated with exposure to particles. The risk is evident for exposure in the previous year, and higher in a 4 year distributed lag model. These risks are significantly greater than seen in time series analyses.
Zanobetti
Antonella
A
Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. azanobet@hsph.harvard.edu
Bind
Marie-Abele C
MA
Schwartz
Joel
J
D000368:Aged; D000369:Aged, 80 and over; D000397:Air Pollution / Q000009:adverse effects*; D002423:Cause of Death; D003430:Cross-Sectional Studies; D004781:Environmental Exposure / Q000032:analysis*; D004784:Environmental Monitoring; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010316:Particle Size; D011379:Prognosis; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000628:therapy; D012042:Registries; D012129:Respiratory Function Tests; D018570:Risk Assessment; D012720:Severity of Illness Index; D016019:Survival Analysis; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D014505:Urban Population