Studies show that the ability to perform simple math problems, as well as handling financial matters, are typically one of the first set of skills to decline in diseases of the mind, like Alzheimer’s, . . . Research has also shown that even cognitively normal people may reach a point where financial decision-making becomes more challenging.
via As Cognition Slips, Financial Skills Are Often the First to Go – NYTimes.com.
This article contains a list of early signs of financial decline in the elderly.