That seems like a problem subject to heavy confirmation bias - e.g. people decide their relative is cognitively impaired and see any transient shortfall as bein

That seems like a problem subject to heavy confirmation bias - e.g. people decide their relative is cognitively impaired and see any transient shortfall as being more evidence, rather than any number of other possible causes. (Not that you can't necessarily see cognitive decline externally earlier than a diagnosis, just that it seems like it'd be hard to make a clinical argument about persistent decline versus several poor nights of sleep, for example.)