1 Unit of Epidemiology and Medical Statistics, Department of Public Health and Community Medicine, University of Verona, Verona, Italy. giuseppe.verlato@univr.it.
2 Sezione di Epidemiologia e Statisca Medica, Istituti Biologici 2B, Strada Le Grazie 8, 37134, Verona, Italy. giuseppe.verlato@univr.it.
3 Unit of Epidemiology and Medical Statistics, Department of Public Health and Community Medicine, University of Verona, Verona, Italy.
4 Department of Medicine, University of Verona, Verona, Italy.
5 Allergy Unit, Ospedali Riuniti di Ancona, Ancona, Italy.
6 Department of Public, Clinical and Preventive Medicine, II University of Naples, Naples, Italy.
7 Department of Public Health and Pediatrics, University of Turin, Turin, Italy.
8 Department of Hygiene, University of Perugia, Perugia, Italy.
9 Department of Internal Medicine, Section of Respiratory Disease, University of Perugia, Perugia, Italy.
10 Institute of Respiratory Diseases, IRCCS San Matteo, Pavia, Italy.
11 Institute of Respiratory Diseases, University of Sassari, Sassari, Italy.
12 Unit of Epidemiology, ASL, 2, Salerno, Salerno, Italy.
13 Unit of Respiratory Medicine, National Health Service (CPA-ASL TO2), Turin, Italy.
14 Department of Public Health, Experimental and Legal Medicine, University of Pavia, Pavia, Italy.