1. Department of Internal Medicine and Rehabilitation , Policlinico di Monza, 20900 Monza , Italy
2. Department of Medicine and Surgery, Università degli Studi di Milano-Bicocca , 20900 Monza , Italy
3. National Centre for Healthcare Research & Pharmacoepidemiology, at the University of Milano-Bicocca , 20126 Milan , Italy
4. Laboratory of Healthcare Research & Pharmacoepidemiology, Unit of Biostatistics, Epidemiology and Public Health, Department of Statistics and Quantitative Methods, University of Milano-Bicocca , 20126 Milan , Italy
5. MOX - Laboratory for Modeling and Scientific Computing, Department of Mathematics, Politecnico di Milano , 20126 Milan , Italy
6. CADS - Center for Analysis Decisions and Society , Human Technopole , 20126 Milan , Italy