Annalisa Davin, Carol Brayne, Xin Yi Gwee, Sanmei Chen, Nicolas Cherbuin, Pierre-Marie Preux, Tze Pin Ng, Richard B. Lipton, Yuda Turana, Ji Won Han, Frank Jessen, Martin P.J. van Boxtel, Normah Che Din, Roberta Vaccaro, Mindy J. Katz, Perminder S. Sachdev, Suzana Shahar, Julian N. Trollor, Fiona E. Matthews, Qi Gao, Javier Santabárbara, Mary Ganguli, Antonio Lobo, Henry Brodaty, Alexander Pabst, Susanne Röhr, Shuzo Kumagai, Marie-Laure Ancelin, Kaarin J. Anstey, Maëlenn Guerchet, Seung Wan Suh, Erin Jacobsen, Darren M. Lipnicki, Cuiling Wang, Antonio Guaita, Sebastian Köhler, Ki Woong Kim, Karen Ritchie, Yvonne Suzy Handajani, Beth E. Snitz, Divya Vanoh, Pascal M'Belesso, Isabelle Carrière, Kenji Narazaki, Blossom C. M. Stephan, Steffi G. Riedel-Heller, Raúl López-Antón, Nicole A. Kochan, John D. Crawford, Psychiatrie & Neuropsychologie, Section Neuropsychology, RS: FPN NPPP I, RS: MHeNs - R1 - Cognitive Neuropsychiatry and Clinical Neuroscience, Occupational Health and Public Health (ISAP), Universität Leipzig [Leipzig]-Occupational Health and Public Health (ISAP)-Institute of Social Medicine, Trinity College Dublin, Faculty of Medicine [Cologne], University Hospital of Cologne [Cologne]-University of Cologne, DZNE, Bonn, Germany, Faculty of Medicine [Jakarta, Indonesia], Universitas Indonesia [Jakarta, Indonesia], Department of Public Health and Primary Care [Cambridge, UK] (Institute of Public Health), University of Cambridge [UK] (CAM), MRC Biostatistics Unit [Cambridge, UK], Institute of Health & Society [Newcastle upon Tyne, UK], Newcastle University [Newcastle], Institute of Health & Society, Saul B. Korey Department of Neurology, Yeshiva University- Albert Einstein College of Medicine [New York], Neuroépidémiologie Tropicale (NET), CHU Limoges-Institut d'Epidémiologie Neurologique et de Neurologie Tropicale-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut Génomique, Environnement, Immunité, Santé, Thérapeutique (GEIST), Université de Limoges (UNILIM)-Université de Limoges (UNILIM), Service de l'Information Médicale et de l'Évaluation [CHU Limoges] (SIME), CHU Limoges, Laboratoire de Biostatistique et d'Informatique Médicale, Université de Limoges (UNILIM), University of Edinburgh, Seoul National University [Seoul] (SNU), Seoul National University Hospital, University Kebangsaan Malaysia, University Sains Malaysia, Partenaires INRAE, Maastricht University Medical Centre (MUMC), Maastricht University [Maastricht], University of Pittsburgh School of Medicine, Pennsylvania Commonwealth System of Higher Education (PCSHE), University of Fukuoka, Röhr, Susanne [0000-0001-9385-0669], and Apollo - University of Cambridge Repository
International audience; Background: Subjective cognitive decline (SCD) is recognized as a risk stage for Alzheimer's disease (AD) and other dementias, but its prevalence is not well known. We aimed to use uniform criteria to better estimate SCD prevalence across international cohorts. Methods: We combined individual participant data for 16 cohorts from 15 countries (members of the COSMIC consortium) and used qualitative and quantitative (Item Response Theory/IRT) harmonization techniques to estimate SCD prevalence. Results: The sample comprised 39,387 cognitively unimpaired individuals above age 60. The prevalence of SCD across studies was around one quarter with both qualitative harmonization/QH (23.8%, 95%CI = 23.3-24.4%) and IRT (25.6%, 95%CI = 25.1-26.1%); however, prevalence estimates varied largely between studies (QH 6.1%, 95%CI = 5.1-7.0%, to 52.7%, 95%CI = 47.4-58.0%; IRT: 7.8%, 95%CI = 6.8-8.9%, to 52.7%, 95%CI = 47.4-58.0%). Across studies, SCD prevalence was higher in men than women, in lower levels of education, in Asian and Black African people compared to White people, in lower- and middle-income countries compared to high-income countries, and in studies conducted in later decades. Conclusions: SCD is frequent in old age. Having a quarter of older individuals with SCD warrants further investigation of its significance, as a risk stage for AD and other dementias, and of ways to help individuals with SCD who seek medical advice. Moreover, a standardized instrument to measure SCD is needed to overcome the measurement variability currently dominant in the field.