NEFL and Alzheimer disease: Similarly, studies have found elevated NfL to be associated with worse cognition or cognitive decline in AD/MCI,8, 10, 42, 50 PD or other synucleinopathies,44, 45, 46, 50, 51, 52, 53 or FTD,54 while others did not.10, 47, 48, 49, 53, 55