The effects of age on rate of progression of Alzheimer disease and dementia with associated cerebrovascular disease

Background: Relatively little is known about how cerebrovascular disease affects progression of dementia. Previous studies have found no differences in progression of Alzheimer disease and vascular dementia, but these studies have not specifically examined age effects. Objective: To test whether the rate of cognitive decline is different in Alzheimer disease compared with dementia with associated cerebrovascular disease in clinical and autopsy patient series. Patients and Methods: We studied the longitudinal course of cognitive function as measured by the Mini-Mental State Examination (MMSE) in patients with clinically and neuropathologically diagnosed conditions evaluated through a university Alzheimer disease center. Clinical patients were grouped according to possible Alzheimer disease without stroke (n=37), probable Alzheimer disease without stroke (n=181), and dementia with stroke (n=50). Autopsy cases were categorized into Alzheimer disease (n=78) and dementia with vascular disease (n=13). Data were analyzed using random-effects modeling of longitudinal change. Results: There was a significant interaction between age ZD and diagnosis in determining rate of change on the MMSE scores for both the clinical and autopsy samples. Rate of change decreased slightly with advancing age for Alzheimer disease groups, but increased with age for dementia with cerebrovascular disease groups. Conclusions: Dementia with cerebrovascular disease declined faster in patients 80 years and older compared with Alzheimer disease without associated cerebrovascular pathological conditions, but showed slower decline in patients younger than 80 years. This effect most likely reflects combined Alzheimer and vascular pathological conditions in older patients with cerebrovascular disease.