Mild senile dementia of the Alzheimer type: 3. Longitudinal and cross-sectional assessment.

Sixty-six subjects diagnosed by validated criteria as having senile dementia of the Alzheimer type (SDAT) were assessed with clinical measures commonly used to study dementia. The severity of the SDAT was mild in 24, moderate in 24, and severe in 18. The data from these three groups in a cross-sectional study were compared with results in our earlier study of 43 subjects enrolled with mild SDAT and followed longitudinally. We concluded that the cross-sectional method underestimates the severity of progression as indicated by some of the clinical measures. Additionally, the 24 new subjects with mild SDAT were assessed longitudinally. This replication study confirmed our earlier conclusions that four of six clinical measures showed similar patterns over time and were useful throughout the study, global measures being more informative than brief individual measures with ceiling or floor effects.