International Journal of Biometeorology

, Volume 47, Issue 4, pp 227–229 | Cite as

Sensitivity analysis of common statistical models used to study the short-term effects of air pollution on health

  • Aurelio TobíasEmail author
  • Marc Sáez
  • Iñaki Galán
  • Michael J. Campbell
Original Article


The relationship between photochemical air pollutants (nitrogen dioxide and ozone) and emergency room admissions for asthma in Madrid (Spain) for the period 1995–1998 was analysed using the statistical models commonly used to studying the short-term effects of air pollution on health: linear and Cochrane-Orcutt regression, standard Poisson and Poisson corrected by overdispersion, Poisson autoregressive models, and generalised additive models. Linear regression models presented residual autocorrelation, Poisson regression models also showed overdispersion, and generalised additive models did not show residual autocorrelation and overdispersion was substantially reduced. Linear models provided biased estimates because our health outcome is non-normally distributed. Estimates from Poisson regression allowing for overdispersion and autocorrelation did not differ substantially from those reported by generalised additive models, which present the best model fit in terms of the absence of autocorrelation and reduction of overdispersion.


Air pollution Statistical models Autocorrelation Overdispersion Sensitivity analysis 



We are grateful to Dr. José Banegas also to the anonymous referees and to the Editor for their useful comments. We would also thank to the Madrid Municipal Air Pollution Control Department (Departamento de Control de Contaminación Atmosférica del Ayuntamiento de Madrid), the Ministry of the Environment Subdirectorate-General for Environmental Quality (Subdirección General de Calidad Ambiental del Ministerio de Medio Ambiente) the Regional Asthma Prevention & Control Programme (Programa Regional de Prevención y Control del Asma) and the Gregorio Marañón Hospital Emergency Ward for allowing us access to their data. This study was funded by the Advisory Committee to the Madrid Regional Asthma Prevention & Control Programme (Comisión Asesora del Programa Regional de Prevención y Control del Asma de la Comunidad de Madrid). Aurelio Tobías was enjoying a postgraduate fellowship of the Universidad Autónoma de Madrid.


  1. Campbell MJ (1998) Time series regression. In: Armitage P, Colton T (eds) Encyclopaedia of Biostatistics. Wiley, New YorkGoogle Scholar
  2. Dominici F, McDermott A, Zeger SL, Samet JM (2002) On the use of generalized additive models in time series of air pollution and health. Am J Epidemiol 156:193–203CrossRefPubMedGoogle Scholar
  3. Katsouyanni K, Touloumi G, Samoli E, Gryparis A, Manopolis Y, Le Tertre A, Boumghar A, Rossi G, Zmirou D, Balleser F, Anderson HR, Wojtyniak B, Paldy A, Braunstein R, Pekkanen J, Schindler J, Schwartz J (2002) Different convergence parameters applied to S-PLUS GAM function. Epidemiology 13:742CrossRefGoogle Scholar
  4. Kelsall JE, Samet JM, Zeger SL, Xu J (1997) Air pollution and mortality in Philadelphia, 1974–1988. Am J Epidemiol 146:750–762PubMedGoogle Scholar
  5. McCullagh P, Nelder JA (1992) Generalized linear models. Chapman & Hall, LondonGoogle Scholar
  6. Samoli E, Schwartz J, Wojtyniak B, Touloumi G, Spix C, Balducci F, Medina S, Rossi G, Sunyer J, Bacharova L, Anderson HR, Katsouyanni K (2001) Investigating regional differences in short-term effects of air pollution on daily mortality in the APHEA project: a sensitivity analysis for controlling long-term trends and seasonality. Environ Health Perspect 109:349–353PubMedGoogle Scholar
  7. Schwartz J (1994) Non-parametric smoothing in the analysis of air pollution and respiratory illness. Can J Stat 4:471–487Google Scholar
  8. Schwartz J, Spix C, Touloumi G, Bacharova L, Barumamdzadeh T, Le Terte A, Piekarksi T, Ponde de Leon A, Ponka A, Rosi G, Saez M, Schouten JP (1996) Methodological issues in studies of air pollution and daily counts of deaths or hospital admissions. J Epidemiol Commun Health 50(Suppl 1):S3–S11Google Scholar
  9. Tobías A, Sunyer J, Samoli E, Katsouyanni K (1999) Contaminación ambiental y mortalidad. Análisis de sensibilidad. Gac Sanit 13:73Google Scholar

Copyright information

© ISB 2003

Authors and Affiliations

  • Aurelio Tobías
    • 1
    • 2
    Email author
  • Marc Sáez
    • 3
  • Iñaki Galán
    • 4
  • Michael J. Campbell
    • 5
  1. 1.Department of Statistics and Econometrics, Universidad Carlos III de Madrid, C/Madrid 126, E-28903 Getafe, Spain
  2. 2.Department of Preventive medicine and Public Health, Universidad Autónoma de Madrid, Spain
  3. 3.Statistics and Econometrics, Applied Economics and Health (GRECS), Department of Economics, Universitat de Girona, Spain
  4. 4.Department of Epidemiology, Institute of Public Health, Consejería de Sanidad, Madrid, Spain
  5. 5.Institute of General Practice and Primary Care, University of Sheffield, UK

Personalised recommendations