Substantial effects of apolipoprotein E ε4 on memory decline in very old age: longitudinal findings from a population-based sample.

We examined associations between the apolipoprotein E (APOE) ε4 allele and levels of performance and rates of change in cognition in late life taking incident dementia into account. The sample consisted of 482 nondemented individuals, aged 80 years and older at baseline, drawn from the OCTO twin study. A battery of 10 cognitive tests was administered at 5 occasions with measurements intervals of 2 years. We fitted hierarchical linear models with time specified as time to death and controlled for baseline age, sex, education, stroke, cardiovascular disease, hypertension, diabetes, and incident dementia. The ε4 allele was significantly associated with lower levels of performance or steeper rate of decline in all 7 memory tests. Largest effect sizes were found in tests of delayed recall and recognition memory. The effects of the APOE ε4 allele were, however, reduced to a nonsignificant level in all tests except 1 after accounting for incident dementia. The findings support the notion that the APOE ε4 allele is associated with substantial memory decline in very old age, but as expected, the effect is largely related to incident dementia.

Dynamic associations of change in physical activity and change in cognitive function: coordinated analyses of four longitudinal studies.

The present study used a coordinated analyses approach to examine the association of physical activity and cognitive change in four longitudinal studies. A series of multilevel growth models with physical activity included both as a fixed (between-person) and time-varying (within-person) predictor of four domains of cognitive function (reasoning, memory, fluency, and semantic knowledge) was used. Baseline physical activity predicted fluency, reasoning and memory in two studies. However, there was a consistent pattern of positive relationships between time-specific changes in physical activity and time-specific changes in cognition, controlling for expected linear trajectories over time, across all four studies. This pattern was most evident for the domains of reasoning and fluency.