Abstract
Characterization of cognitive profiles across genetic FTD gene mutations is crucial for the identification of sensitive endpoints for clinical trials targeting specific pathologies. However, no systematic overview of the literature describing cognitive profiles in different FTD gene mutations has been made thus far. We performed a meta-analysis and systematic review to characterize cognitive profiles across the different FTD gene mutations and clinical disease stages of familial frontotemporal dementia (FTD). We included 27 studies comparing presymptomatic (n=1027), and/or symptomatic (n=574) mutation carriers (GRN, MAPT, C9orf72) with controls (n=1296). We extracted cognitive data and grouped them into six cognitive domains (language, attention and mental processing speed, executive function (EF), memory, social cognition, and visuospatial abilities). These domains were further subdivided into specific cognitive sub-processes. We calculated Hedges' g and performed multilevel meta-analyses per cognitive domain and FTD gene mutation comparing presymptomatic and symptomatic mutation carriers to controls. Moderator analyses were performed to the effect of age, education, sex, and cognitive subprocess. Eleven studies into rarer FTD mutations were included in the systematic review. Presymptomatic GRN mutation carriers showed deficits in EF, and presymptomatic C9orf72 mutation carriers in language, EF, and attention. Presymptomatic MAPT mutation carriers did not differ from controls on any of the cognitive domains. All symptomatic mutation carriers had deficits in language, EF, attention, and memory. Both in the presymptomatic and symptomatic stage cognitive sub-processes for language, attention and mental processing speed, EF, and memory were differentially affected in GRN, MAPT, and C9orf72. Cognitive decline was present in the presymptomatic stage of GRN and C9orf72 mutation carriers, but not MAPT mutation carriers. Unique cognitive sub-processes were affected in GRN, MAPT, and C9orf72. This study increased our knowledge of the cognitive deficits in familial FTD, which can aid in differential diagnosis and selection of endpoints for clinical trials.