The evidence that the protective and pathogenic Swedish mutations have opposite effects on APP processing by β- and α-secretases, that is decreased β-cleavage and increased α-cleavage for the former and increased β-cleavage and decreased α-cleavage for the latter, is striking and may suggest that protection from and pathogenesis of dementia may depend upon a complex alteration in APP metabolites and their functions rather than simply on Aβ levels. Here, APP is linked to dementia.