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Respiration. 2004 Mar-Apr;71(2):134-7.

Visits to the emergency room for asthma attacks and short-term variations in air pollution. A case-crossover study.

Author information

1
Department of Chest Diseases and Allergy, Hopital Nord, and UPRES Equipe d'Accueil No. 1784 Biogénotoxicologie et mutagénèse environnementale - IFR 112: Pôle Méditerranéen des Sciences de l'Environnement, Marseille, France.

Abstract

BACKGROUND:

The 'case-crossover' design is a strategy fitted to studying transient effects of intermittent exposure on acute-onset disease occurring shortly after exposure. It has the important advantage of eliminating most confounding variables, allowing a stronger causality inference.

OBJECTIVES:

The objective of the study was to evaluate the relationships between emergency room (ER) visits for asthma attacks and gaseous air pollution changes.

METHODS:

The study included 549 individuals, 3-49 years old, visiting the ER during 1 year. Exposure to gaseous air pollutants (SO2, NO2, O3) on the same day and up to 4 days before was computed according to the patient's address. The statistical analysis included meteorological data as potential confounding variables.

RESULTS:

No association could be shown between ER visits and SO2 or NO2 levels. In contrast, there was a statistically significant association between ER visits and mean O3 levels, on the day of admission and also on D -2 and D -3. For an increase of 10 microg/m3, the risk of requiring an ER admission increased by 6-10%.

CONCLUSIONS:

Using this new strategy, we confirmed that ozone changes lead to a moderate increase in risk of requiring an ER admission in asthmatic subjects.

PMID:
15031567
DOI:
10.1159/000076673
[Indexed for MEDLINE]

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