We determined the rates of cognitive change associated with twenty
individual measures. Participants included 547 noninstitutionalized
septuagenarians and octogenarian residents of a comprehensive care
retirement community who were studied over three years. Latent growth
curves (LGC) of multiple cognitive measures were compared to a LGC model
of the rates of change in Activities of Daily Living (ADL) and
Instrumental Activities of Daily Living (IADL). All curves were
standardized relative to each variable's baseline distribution.
Baseline scores were within their expected normal age-specific ranges.
Most measures showed significant rates of change over time. There was also
significant variability about those rates, suggesting clinical
heterogeneity. Many deteriorated over time, as did ADLs and IADLs.
However, performance on some measures improved, consistent with learning
effects. The rates of change in two measures, the Executive Interview and
the Trail Making Test, were closely related to decline in IADLs. These
results suggest that age-related cognitive decline is a dynamic
longitudinal process affecting multiple cognitive domains. Heterogeneity
in the rates of cognitive change may reflect the summed effects of age and
comorbid conditions affecting cognition. Some measures may be ill-suited
for measuring age-related changes in cognition, either because they are
insensitive to change, or hindered by learning effects. Nonverbal measures
appear to be particularly well suited for the prediction of age-related
functional decline. These observations are relevant to the definition and
diagnosis of “dementing” conditions. (JINS, 2005,
11, 899–909.)