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. 1999 Aug;107(8):629–631. doi: 10.1289/ehp.99107629

A case-crossover analysis of air pollution and mortality in Philadelphia.

L M Neas 1, J Schwartz 1, D Dockery 1
PMCID: PMC1566488  PMID: 10417359

Abstract

This study reassessed Schwartz and Dockery's analysis of daily mortality from nonexternal causes among residents of Philadelphia, Pennsylvania, over 8 years, from 1973 to 1980 [American Review of Respiratory Disease 145:600-604 (1992)]. A Poisson regression analysis using the same model found that a 100-microg/m(3) increment in the 48-hr mean concentration of total suspended particulates (TSP) was associated with increased all-cause mortality [rate ratio = 1.069; 95% confidence interval (CI), 1.043-1.096) after adjustment for quadratic trend, season, year, previous day's mean temperature, dew point, winter temperature, and indicators of hot (temperature > 80 degrees F) and humid days (dew point > 66 degrees F). Critics suggested that time-varying factors such as season and day of week were not sufficiently controlled in this analysis and subsequent studies in other locations. We used a conditional logistic regression analysis with a case-crossover design to reanalyze the data, with air pollution in the prior and subsequent weeks to the day of death serving as referent periods. The case-crossover approach controls for season and day of week by design rather than modeling. We found that a 100-microg/m(3) increment in the 48-hr mean level of TSP was associated with increased all-cause mortality [odds ratio (OR) = 1.056; CI, 1.027-1.086) after adjustment for the same weather variables as above. Similar associations were observed for deaths in individuals over 65 years of age (OR = 1.074; CI, 1. 037-1.111) and for deaths due to cardiovascular disease (OR = 1.063; CI, 1.021-1.107). The current case-crossover analysis confirms the general conclusion of the previous Poisson regression analysis of an association of TSP with daily mortality in Philadelphia, Pennsylvania.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Kelsall J. E., Samet J. M., Zeger S. L., Xu J. Air pollution and mortality in Philadelphia, 1974-1988. Am J Epidemiol. 1997 Nov 1;146(9):750–762. doi: 10.1093/oxfordjournals.aje.a009351. [DOI] [PubMed] [Google Scholar]
  2. Maclure M. The case-crossover design: a method for studying transient effects on the risk of acute events. Am J Epidemiol. 1991 Jan 15;133(2):144–153. doi: 10.1093/oxfordjournals.aje.a115853. [DOI] [PubMed] [Google Scholar]
  3. Mittleman M. A., Maclure M., Robins J. M. Control sampling strategies for case-crossover studies: an assessment of relative efficiency. Am J Epidemiol. 1995 Jul 1;142(1):91–98. doi: 10.1093/oxfordjournals.aje.a117550. [DOI] [PubMed] [Google Scholar]
  4. Mittleman M. A., Maclure M., Robins J. M. Control sampling strategies for case-crossover studies: an assessment of relative efficiency. Am J Epidemiol. 1995 Jul 1;142(1):91–98. doi: 10.1093/oxfordjournals.aje.a117550. [DOI] [PubMed] [Google Scholar]
  5. Mittleman M. A., Maclure M., Sherwood J. B., Mulry R. P., Tofler G. H., Jacobs S. C., Friedman R., Benson H., Muller J. E. Triggering of acute myocardial infarction onset by episodes of anger. Determinants of Myocardial Infarction Onset Study Investigators. Circulation. 1995 Oct 1;92(7):1720–1725. doi: 10.1161/01.cir.92.7.1720. [DOI] [PubMed] [Google Scholar]
  6. Mittleman M. A., Maclure M., Tofler G. H., Sherwood J. B., Goldberg R. J., Muller J. E. Triggering of acute myocardial infarction by heavy physical exertion. Protection against triggering by regular exertion. Determinants of Myocardial Infarction Onset Study Investigators. N Engl J Med. 1993 Dec 2;329(23):1677–1683. doi: 10.1056/NEJM199312023292301. [DOI] [PubMed] [Google Scholar]
  7. Moolgavkar S. H., Luebeck E. G., Hall T. A., Anderson E. L. Air pollution and daily mortality in Philadelphia. Epidemiology. 1995 Sep;6(5):476–484. doi: 10.1097/00001648-199509000-00003. [DOI] [PubMed] [Google Scholar]
  8. Samet J., Zeger S., Kelsall J., Xu J., Kalkstein L. Does weather confound or modify the association of particulate air pollution with mortality? An analysis of the Philadelphia data, 1973-1980. Environ Res. 1998 Apr;77(1):9–19. doi: 10.1006/enrs.1997.3821. [DOI] [PubMed] [Google Scholar]
  9. Schwartz J. Air pollution and daily mortality in Birmingham, Alabama. Am J Epidemiol. 1993 May 15;137(10):1136–1147. doi: 10.1093/oxfordjournals.aje.a116617. [DOI] [PubMed] [Google Scholar]
  10. Schwartz J. Air pollution and daily mortality: a review and meta analysis. Environ Res. 1994 Jan;64(1):36–52. doi: 10.1006/enrs.1994.1005. [DOI] [PubMed] [Google Scholar]
  11. Schwartz J., Dockery D. W. Increased mortality in Philadelphia associated with daily air pollution concentrations. Am Rev Respir Dis. 1992 Mar;145(3):600–604. doi: 10.1164/ajrccm/145.3.600. [DOI] [PubMed] [Google Scholar]
  12. Schwartz J., Spix C., Touloumi G., Bachárová L., Barumamdzadeh T., le Tertre A., Piekarksi T., Ponce de Leon A., Pönkä A., Rossi G. Methodological issues in studies of air pollution and daily counts of deaths or hospital admissions. J Epidemiol Community Health. 1996 Apr;50 (Suppl 1):S3–11. doi: 10.1136/jech.50.suppl_1.s3. [DOI] [PMC free article] [PubMed] [Google Scholar]

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