Reductions in cholinergic function occur in Alzheimer disease (AD) and dementia with Lewy bodies and correlate with cognitive decline. However, whether such alterations appear in early-stage disease is unclear.
To examine the timing of cholinergic deficits in AD and dementia with Lewy bodies.
Autopsy series of 89 patients with AD and 50 patients with the Lewy body variant of AD (LBV). Stage of disease was stratified according to results of the last Mini-Mental State Examination (MMSE) before death as mild, moderate, severe, or very severe. We analyzed choline acetyltransferase (ChAT) activity in the midfrontal, superior temporal, and inferior parietal cortices.
Although compared with a normal control group ChAT activity was decreased in the AD and LBV cohorts, ChAT activity reduction for the LBV cohort was much greater. Moreover, although the decline in ChAT activity in the AD cohort compared with the normal control group was significant only for patients in later stages of the illness, the decline in the LBV cohort was significant for those who died with mild-stage disease. When less impaired patients in each cohort (MMSE, ≥10) underwent separate analysis, the relationship of ChAT activity with the MMSE score was strong and significant for the LBV cohort alone.
Although cholinergic deficits are seen in both AD and LBV, loss of ChAT activity is less severe and occurs later in the clinical course of AD. Conversely, in LBV, loss of ChAT activity is already prominent in the earliest stages of the illness, suggesting that cholinergic replacement therapy may be more effective in LBV than in AD, especially in mild-stage disease.