Memory is what most people think about when they think about Alzheimer's disease , and it is true that memory is affected early in the illness. The problem, however, is that memory complaints are very common as people get older. Therefore, until very old age (say about 95 years old) most people with memory complaints do not have dementia. How to sort out those who do and those who do not is a major task for physicians, but it boils down to two features: does the person with a memory complaint also have impairment in other areas, such as language, calculation, attention and concentration? Do these impairments interfere with function? I sometimes tell patients that there used to be a joke about people who were worried whether they drank too much. The joke was that you only really had a problem if you drank more than your doctor did. These days, the joke is that you only have a memory problem if your memory is worse than your doctor's. The point is to show people that most people complain of their memory as they get older (roughly, any time after your 30's). Not everyone is reassured by this, however.