Does engagement augment cognitive function or delay disease onset?
Whether any protective effect of social engagement applies chiefly to improved cognition within normal aging or whether it extends to dementia in general or Alzheimer’s disease in particular, where it has been argued that social engagement might prevent or delay the onset or affect the course of the disease, must be considered. The question of whether the onset of dementia can be delayed is particularly difficult to investigate, and we do not want to underestimate the profound difficulties in establishing causal direction from engagement to cognition. Because dementia has a long and insidious onset, cognitive changes may begin to occur well before there is clinical recognition of any dementia (Elias et al., 2000). Thus, it is particularly important to be sure that reduced social interaction is not a consequence of the beginning of cognitive decline. Some analytic innovations may be helpful with epidemiological datasets in which risk factors can be both predictors and outcomes of subseq
