2 Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's, PT Government Associate Laboratory, Braga/Guimarães, Portugal; EPIUnit, Public Health Institute, University of Porto, Porto, Portugal.
3 EPIUnit, Public Health Institute, University of Porto, Porto, Portugal; Occupational Health Department, Centro Hospitalar de Vila Nova de Gaia/Espinho, Vila Nova de Gaia, Portugal.
4 Department of Mathematics, Faculty of Sciences, University of Porto, Porto, Portugal; Centre of Mathematics, University of Porto, Porto, Portugal.
5 EPIUnit, Public Health Institute, University of Porto, Porto, Portugal; Pulmonology Department, Centro Hospitalar de Vila Nova de Gaia/Espinho, Vila Nova de Gaia, Portugal; Department of Clinical Epidemiology, Predictive Medicine and Public Health, Faculty of Medicine, University of Porto, Porto, Portugal.