GFAP and frontotemporal dementia: Moreover, we could not find a significant correlation between GFAP level and disease duration, which contradicts previous studies that found correlations between serum GFAP levels and longitudinal brain atrophy rates, survival time and executive functioning.22 32 It should be noted that while disease duration, brain atrophy, mortality rate and neuropsychological scores are often considered as indicators of disease severity, they actually measure distinct aspects of disease progression in FTD.