Measuring Cognitive Reserve (CR) – A systematic review of measurement properties of CR questionnaires for the adult population.

Aim: The aim of this systematic review was to summarize and critically appraise the quality of published literature on measurement properties of questionnaires assessing Cognitive Reserve (CR) in adults (>18 years). Methods: We systematically searched for published studies on MEDLINE, PsycINFO, and Web of Science through August 2018. We evaluated the methodological quality of the included studies and the results on measurement properties based on a consensus-based standard checklist. Results: The search strategy identified 991 publications, of which 37 were selected evaluating the measurement properties of six different questionnaires. Construct validity of the Cognitive Reserve Index questionnaire was most extensively evaluated, while evaluation of the remaining measurement properties of this questionnaire was scarce. Measurement properties of the Cognitive Reserve Questionnaire and the Cognitive Reserve Scale were assessed more completely. While the Lifetime of Experience Questionnaire seems to be the most thorough instrument, a finale recommendation for one specific questionnaire cannot be drawn, since about half of the measurement properties for each questionnaire were poorly or not assessed at all. Conclusions: There is a need of high quality methodological studies assessing measurement properties of CR questionnaires, especially regarding content validity, structural validity, and responsiveness. Trial registration: PROSPERO Registration number . [ABSTRACT FROM AUTHOR]