Liesbeth Claassen 1, 2, Frans Greven 3, Fred Woudenberg 4, Frans Duim 3, Danielle Timmermans 1, 2
1 Department of Public and Occupational Health, Amsterdam Public Health research institute, VU University Medical Center, 1091 BT, Amsterdam, Netherlands, 2 National Institute for Public Health and the Environment, 3720 BA, Bilthoven, Netherlands, 3 Municipal Health Service, Groningen, 9713 GW, Groningen, Netherlands, 4 Municipal Health Service, Amsterdam, 1000 CE, Amsterdam, Netherlands