1. TransLab Research Group (Ms Blanco-Silvente and Drs Castells and Capellà), and Department of Medical Sciences, University of Girona, Spain (Ms Blanco-Silvente and Drs Castells, Saez, Garre-Olmo, Vilalta-Franch, and Capellà); Research Group on Statistics, Econometrics and Health, University of Girona, Spain (Drs Saez and Barceló); CIBER of Epidemiology and Public Health, Spain (Drs Saez and Barceló); Girona Biomedical Research Institute, Salt, Spain (Drs Garre-Olmo and Vilalta-Franch).