Personality changes in later life are:

a) rare in healthy people. People stay pretty much the same throughout life.
b) normal because experience makes people very different than they were as children and young adults.
c) inevitable because people become cranky and difficult as they age.

When an older person shows significant personality or behavior changes, it is usually a sign that something else is wrong. For example, a person who becomes suddenly and persistently irritable and pessimistic may be suffering from depression.