BDNF and early-onset autosomal dominant Alzheimer disease: Cognition may be influenced by genetic factors such as the possession of a Met allele on the gene encoding brain-derived neurotrophic factor (BDNF), which is associated with poorer cognition [15], and the APOE-ε4 variant coding for the apolipoprotein E protein, an important predictor for the development of Alzheimer’s disease and poorer cognitive performance in older adults [16].