Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden. Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. Center for Assessment of Medical Technology, Örebro University Hospital, Örebro University, Örebro, Sweden. Department of Health Statistics, Second Military Medical University, Shanghai, China. Faculty of Health and Social Sciences, Inland Norway University of Applied Sciences, Elverum, Norway. Research department, Innlandet Hospital Trust, Brumunddal, Norway. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, Örebro, Sweden.