Institution: | 1. National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland;2. Health Centre, Social Services Department, Services for Elderly, City of Helsinki, Finland;3. Department of Applied Chemistry and Microbiology, University of Helsinki, Finland;4. Unit of General Practice, Helsinki University Central Hospital, Finland;5. Department of General Practice and Primary Health Care, University of Helsinki, Finland |