Robert Epstein raises an important point regarding our recent study that being intellectually active was associated with a reduced risk of later developing Alzheimer’s disease. Because Alzheimer’s disease develops gradually over several years, we, too, were concerned that reduced cognitive activity might be an early sign of disease rather than a factor associated with the development of disease. But this did not seem to be the case.
First, the study was longitudinal in design, meaning that we assessed cognitive activity among people without dementia and performed annual evaluations to document the development of disease.
Second, we also measured the rate at which people declined on psychological tests and found that those who were more cognitively active declined slower than those who were less active.
Finally, the results were unchanged when we excluded people who began the study with memory impairment, the first sign of Alzheimer’s, or when we accounted for other factors associated with the development of disease.
Together these data provide compelling evidence that the association is true and quite likely causal. The fact that recent literature demonstrates that the aging brain is capable of much greater plasticity than previously thought lends further confidence in our findings.
Ultimately a complete understanding of the relation of cognitive activity with Alzheimer’s disease will require clinical-pathological studies and evaluations of cognitive interventions.
