Erythrocyte acetyl cholinesterase in elderly patients with dementia and depression compared with normal controls.

A reference range for erythrocyte acetyl cholinesterase (EAChE) in 46 mentally normal subjects aged 65 years or over has been established. Previous reports of a relationship between changes in (EAChE) levels and mental illness (dementia and depression) in the elderly suggested that this determination may be useful in screening elderly subjects for these illnesses or as an aid to diagnostic classification. A study of normal and mentally ill elderly subjects in the community in Liverpool does not confirm a relationship with either senile dementia or depression and many of the changes in EAChE levels noted previously can be accounted for either by variations in the haematocrit or by a hitherto unreported lowering of EAChE levels in normal women over 80 years of age.