Elucidating the factors that mitigate the effects of COVID-19 on cognitive function offers important insights for public health policy and intervention. This systematic review and individual participant data (IPD) meta-analysis assesses cognitive reserve (CR) as a potential moderator of post-COVID-19 cognitive dysfunction (PCCD). Under PRISMA-IPD guidelines, data searches were conducted via PubMed, PsycINFO, Scopus, and Embase, up to January 2023. Eligible studies included at least one cognitive assessment, CR proxy, and disease severity indicator. Of 5,604 studies, 87 were eligible (10,950 COVID-19 cases
78,305 controls), and IPD was obtained for 29 datasets (3,919 COVID-19 cases
8,267 controls). Three-level random-effects meta-analyses indicated that CR had a moderate positive association (r