Glasmacher SA, et al. - Given that a survival disadvantage is conferred by the c9orf72 repeat expansion (c9 or c9orf72^RE) in amyotrophic lateral sclerosis (ALS), and there exists uncertainty regarding its influence on prognosis in frontotemporal dementia (FTD), in view of this information, researchers performed this meta-analysis to assess the prognostic factors in c9ALS, c9FTD, c9ALS-FTD, and atypical phenotypes. They found studies describing disease duration for patients with an established c9orf72^RE and a neurological and/or psychiatric disorder, from the MEDLINE, Embase, Amed, ProQuest, PsychINFO, CINAHL, and LILACS databases. This analysis involved 1,060 c9orf72^RE carriers. In c9ALS, c9FTD, and c9ALS-FTD, a shorter survival was reported in relation to older age at onset. Shorter survival in c9ALS was reported in correlation with bulbar onset. Heterogeneity was evident in the clinical phenotypes observed in patients with neuropathologically confirmed frontotemporal lobar degeneration–TDP-43, motor neuron disease–TDP-43 and frontotemporal lobar degeneration–motor neuron disease–TDP-43, and survival was influenced by these clinical phenotypes. In c9orf72^RE disorders, many factors related to survival were unveiled in this study. There was no significant link of the observed prognostic factors with the bias indicators analyzed.