Mary, a retired accountant in in her early seventies, keeps losing her keys and asks the same questions over and over again. to avoid forgetting, she often makes a list of things she has to do but always forgets to look at them later. she also requires more assistance in managing her finances. mary is most likely in the early stages of

This would be early stages of dementia. 

Dementia is a gradual illness that has neuronal cause in the elderly, during which the memory and other cognitive functions are lost. 

People typically loose the more recently acquired memories first, and they can only remember their childhood. In the later stages of dementia they often loose the ability to speak and to interact with others. 

Mary is in her early stages of dementia.

 at this stage ,senior citizens tend to forget current events and remember those that happened in their childhood.  If left untreated, dementia results to complete loss of memory, and skills as well as speech.
 The causes of dementia are numerous, often genetic predisposition playing a pivot role.