1. National Public Health Institute, Department of Epidemiology and Health Promotion, Health Promotion Research Unit, Mannerheimintie 166, FIN-00300 Helsinki, Finland, mikko.t.laaksonen@helsinki,fi
2. National Public Health Institute, Department of Epidemiology and Health Promotion, Health Promotion Research Unit, Mannerheimintie 166, FIN-00300 Helsinki, Finland
3. Department of Public Health, P.O. Box 41, FIN-00014 University of Helsinki, Finland