Changes in cognitive functioning associated with normal aging.

The present study explores age-related changes in cognitive functioning in a cohort of 122 healthy elderly volunteer subjects over a 3-year period. The sample was partitioned into four age groups: 57-65, 66-70, 71-75, 76-85 years. The results suggested high stability of factor structure over three testing probes, as well as selective attrition effect with significantly lower performance in those subjects, who dropped out from the study on the tests of verbal memory and mental speed. The results of repeated measures MANOVA on raw scores and univariate ANOVAs on factor scores comparing four age groups at each testing probe revealed a differential pattern of changes in verbal and nonverbal perception/memory versus mental speed/mental flexibility. Implications of these findings in clinical diagnostics were considered.