1. Kirkkonummi Health Center, Kirkkonummi, Finland;
2. Department of General Practice, Unit of Primary Health Care, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland;
3. Mutual Insurance Company, Etera, Finland;
4. Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland;
5. General Practice, School of Primary, Aboriginal and Rural Health Care, University of Western Australia, Perth, Australia