Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the mammalian brain. Preclinical studies suggest that BDNF influences the pathophysiology of Alzheimer’s disease. In humans, higher blood BDNF levels have been associated with a lower risk of dementia. However, the relationship between serum BDNF levels and the progression to mild cognitive impairment (MCI) in cognitively normal (CN) individuals remains uncertain.