Institute of Clinical Medicine/Neurology, University of Eastern Finland, Kuopio, Finland. Public Health Promotion Unit, Finnish Institute for Health and Welfare, Helsinki, Finland. Division of Clinical Geriatrics, Center for Alzheimer Research, NVS, Karolinska Institutet, Stockholm, Sweden. Department of Clinical Radiology, Kuopio University Hospital, Finland. Center for Life Course Health Research/Geriatrics, University of Oulu, Finland. Medical Research Center Oulu, Oulu University Hospital and Oulu City Hospital, Finland. Division of Clinical Neurosciences, Turku University Hospital, Finland. Turku PET Centre, University of Turku, Finland. Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland. Joint Municipal Authority for North Karelia Social and Health Services, Joensuu, Finland. Department of Public Health Solutions, National Institute for Health and Welfare Helsinki, Finland. Combinostics, Tampere, Finland. University of Helsinki, Clinicum, and Helsinki University Hospital, Finland. Department of Public Health, University of Helsinki, Finland. South Ostrobothnia Central Hospital, Seinäjoki, Finland. Department of Neurosciences and Preventive Medicine, Danube-University Krems, Austria. Diabetes Research Group, King Abdulaziz University, Jeddah, Saudi Arabia. Neurocenter, Neurology, Kuopio University Hospital, Finland. Ageing Epidemiology (AGE) Research Unit, School of Public Health, Imperial College London, UK.