1. Department of Health Promotion and Chronic Disease Prevention, National Institute for Health and Welfare, 00300 Helsinki, Finland
2. MRC Epidemiology Resource Centre, University of Southampton, Southampton SO16 6YD, UK
3. Heart Research Center, Oregon Health and Science University, Portland, OR 97239, USA
4. Department of General Practice and Primary Health Care, University of Helsinki, P. O. Box 20, 00014 Helsinki, Finland
5. Unit of General Practice, Helsinki University Central Hospital, P. O. Box 705, 00029 HUS, Finland