Related Experiment Video
Updated: Aug 25, 2026

Bronchial Thermoplasty: A Novel Therapeutic Approach to Severe Asthma
Published on: November 4, 2010
Visits to the emergency room for asthma attacks and short-term variations in air pollution. A case-crossover study
S Boutin-Forzano1, N Adel, L Gratecos
1Department 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.
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.
Related Concept Videos
Asthma III: Clinical Manifestations
Asthma-I: Introduction
Asthma-III: Symptoms and Complications
Classification of Asthma
Asthma I: Introduction
Asthma-IV: Diagnostic and Management
Clinical Assessment for Asthma:
This is the first step in diagnosing and managing asthma. It includes:
Chronic Obstructive Pulmonary Disease III: Chronic Bronchitis Features