1 National Institute for Public Health and the Environment, Bilthoven, the Netherlands, Public Health Service Utrecht, Zeist, the Netherlands, European Programme for Intervention and Epidemiology Training, Stockholm, Sweden Public Health Service Groningen, Groningen, the Netherlands Department of Otorhinolaryngology, Head and Neck Surgery-Brain Center, Rudolf Magnus, University Medical Center Utrecht, the Netherlands National Institute for Public Health and the Environment, Bilthoven, the Netherlands Department of Otorhinolaryngology, BovenIJ ziekenhuis, Amsterdam, the Netherlands National Institute for Public Health and the Environment, Bilthoven, the Netherlands.