A recent study also found that the level of PCSK9 in the cerebrospinal fluid of AD patients was higher than that of non-AD patients, indicating that there is a pathophysiological link between PCSK9 and AD, and PCSK9 may play a role in AD by activating lipid accumulation, apoptosis and amyloid production in the brain [48]. This evidence concerns the gene PCSK9 and Alzheimer disease.