Cholinergic markers in elderly patients with early signs of Alzheimer disease

Context A central tenet of Alzheimer disease (AD) is the loss of cortical c holinergic function and cholinergic markers in postmortem brain specimens. Whether these profound deficits in cholinergic markers found in end-stage p atients are also found in patients with much earlier disease is not known. Objective To determine whether cholinergic deficits in AD precede, follow, or occur in synchrony with the earliest signs of cognitive deterioration. Design, Setting, and Patients Postmortem study of nursing home residents wi th Clinical Dementia Rating (CDR) Scale scores of 0.0 to 2.0 and 4.0 to 5.0 who underwent autopsy between 1986 and 1997, comparing the activity of the cholinergic marker enzymes in the cortices of 66 elderly subjects with no (CDR score = 0.0; n = 18), questionable (CDR score = 0.5; n = 11), mild (CD R score = 1.0; n = 22), or moderate (CDR score = 2.0; n = 15) dementia vs s ubjects with severe dementia (CDR score = 4.0-5.0; n = 15). Main Outcome Measures Activity of the cholinergic marker enzymes choline ac etyltransferase and acetylcholinesterase in 9 neocortical brain regions. Results The activity of choline acetyltransferase and acetylcholinesterase in 9 neocortical brain regions did not differ significantly in subjects wit h CDR scores of 0.0 to 2.0, but was significantly lower in subjects with se vere dementia (CDR score = 4.0-5.0), Choline acetyltransferase levels were significantly correlated with severity of neuropathological lesions of AD, as measured by density of neuritic plaques and neurofibrillary tangles. Conclusions Although neocortical cholinergic deficits are characteristic of severely demented AD patients, in this study, cholinergic deficits were no t apparent in individuals with mild AD and were not present until relativel y late in the course of the disease. These results suggest that patients wi th more severe disease should be a target for cholinergic treatment.