BDNF and early-onset autosomal dominant Alzheimer disease: Additionally, the literature mentioned that proBDNF and BDNF levels decrease in the pre-clinical stages of Alzheimer’s disease [31], and insomnia and cognitive decline are common risk factors associated with developing neurodegenerative diseases [32]; hence, our results may be considered for further studies to validate the potential use of proBDNF and BDNF levels as biomarkers for the classification of different stages of neurodegenerative diseases in older adults.