BCHE and Cognitive impairment: In Alzheimer's disease, cognitive impairment may occur decades prior to the diagnosis1 which reflects ongoing accumulation of neurodegenerative protein and associated cellular dysfunction and death.2 Following diagnosis, comparison of cognitive trajectories provides an index of response to treatment such as cholinesterase inhibitors3 and the recently described amyloid immunotherapies.4,5 In other neurological conditions that may cause cognitive impairment, however, pre- and post-diagnosis cognitive profiles are largely unknown.