BACKGROUND: Although sensitizer-induced occupational asthma (OA) accounts for an appreciable fraction of adult asthma, the severity of OA has received little attention. OBJECTIVE: The aim of this study was to characterize the burden and determinants of severe OA in a large multicenter cohort of subjects with OA. METHODS: This retrospective study included 997 subjects with OA ascertained by a positive specific inhalation challenge completed in 20 tertiary centers in 11 European countries during the period 2006 to 2015. Severe asthma was defined by a high level of treatment and any 1 of the following criteria: (1) daily need for a reliever medication, (2) 2 or more severe exacerbations in the previous year, or (3) airflow obstruction. RESULTS: Overall, 162 (16.2%; 95% CI, 14.0%-18.7%) subjects were classified as having severe OA. Multivariable logistic regression analysis revealed that severe OA was associated with persistent (vs reduced) exposure to the causal agent at work (odds ratio [OR], 2.78; 95% CI, 1.50-5.60); a longer duration of the disease (OR, 1.04; 95% CI, 1.00-1.07); a low level of education (OR, 2.69; 95% CI, 1.73-4.18); childhood asthma (OR, 2.92; 95% CI, 1.13-7.36); and sputum production (OR, 2.86; 95% CI, 1.87-4.38). In subjects removed from exposure, severe OA was associated only with sputum production (OR, 3.68; 95% CI, 1.87-7.40); a low education level (OR, 3.41; 95% CI, 1.72-6.80); and obesity (OR, 1.98; 95% CI, 0.97-3.97). CONCLUSIONS: This study indicates that a substantial proportion of subjects with OA experience severe asthma and identifies potentially modifiable risk factors for severe OA that should be targeted to reduce the adverse impacts of the disease.

Cardio Thoracic and Vascular Department University of Pisa Pisa Italy

Department of Allergy Fundacion Jimenez Dıaz and CIBER de Enfermedades Respiratorias Madrid Spain

Department of Allergy Hospital La Paz Institute for Health Research Madrid Spain

Department of Allergy Skin and Allergy Hospital Helsinki University Central Hospital Helsinki Finland

Department of Chest Medicine Centre Hospitalier Universitaire UCL Namur Université Catholique de Louvain Yvoir Belgium

Department of Medicine Section of Occupational Medicine Respiratory Diseases and Occupational and Environmental Toxicology University of Perugia Perugia Italy

Department of Occupational and Environmental Medicine Royal Brompton Hospital and Imperial College Royal Brompton and Harefield NHS Foundation Trust London United Kingdom

Department of Occupational Diseases and Environmental Health Nofer Institute of Occupational Medicine Lodz Poland

Department of Occupational Medicine 1st Faculty of Medicine Charles University Prague Czech Republic

Department of Occupational Medicine Haukeland University Hospital Bergen Norway

Department of Public Health Experimental and Forensic Medicine University of Pavia and Allergy and Immunology Unit Istituti Clinici Scientifici Maugeri IRCCS Pavia Italy

Department of Pulmonary Medicine and Occupational Medicine Odense University Hospital Odense Denmark

Department of Respiratory Medicine North Manchester General Hospital Manchester United Kingdom

Division of Asthma and Allergy Department of Chest Diseases University Hospital of Strasbourg and Fédération de Médecine translationnelle Strasbourg University Strasbourg France

Groupe Méthode Recherche Clinique Pôle de Santé Publique Strasbourg University Strasbourg France

Institute for Occupational and Maritime Medicine University Medical Center Hamburg Eppendorf Hamburg Germany

Institute for Prevention and Occupational Medicine of the German Social Accident Insurance Ruhr University Bochum Germany

Occcupational Medicine Finnish Institute of Occupational Health Helsinki Finland

Occupational Lung Disease Unit Birmingham Heartlands Hospital Birmingham United Kingdom

Servei Pneumologia Hospital Vall d'Hebron Universitat Autonoma de Barcelona and CIBER de Enfermedades Respiratorias Barcelona Spain

Unit of Occupational Medicine and Public Health University of Padova Padova Italy

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