The overall goal of this project is to examine whether cognitive status and cognitive change in middle age are predictive of rate of subsequent decline. While stability is the normative pattern for most mental abilities in midlife, longitudinal studies of normal aging have reported subgroups of middle-aged adults who show reliable decline or improvement on specific cognitive abilities. Adults who exhibit early decline in midlife on select abilities may be at higher risk for an accelerated rate of cognitive decline in old age. Study participants (N = 573) will be members from the Seattle Longitudinal Study (SLS) with longitudinal cognitive data obtained during middle-age (32-60 years). SLS members were assessed on 6 mental abilities (verbal, spatial orientation, reasoning, number, fluency, and memorydelayed recall). The impact of midlife cognition will be studied for two cohorts. For the Older Cohort (b1914 - 1941; M age = 74; N = 308) cognitive data are available in midlife and also in old age. For the Middle Age Cohort (b1942 - 1962; N = 265; M age = 56) cognitive change data are available in midlife. A Cognitive Risk profile in midlife has been developed for each participant, indicating a pattern of cognitive risk, stability, or gain in middle age. The sample will be further characterized by neuropsychological assessment, APOE genotyping, and health histories. To examine brain volume as a mediator of cognitive change, baseline measures and rate of atrophy in the hippocampus, entorhinal cortex, and frontal lobe will be assessed by structural MRI at two occasions. Longitudinal data on participants' engagement in stimulating cognitive activities will also be studied as a mediator of cognitive change. The primary dependent variable will be rate of change in cognitive functioning. [unreadable] [unreadable]