Healthy people can experience memory loss or memory distortion at any age. Some of these memory flaws become more pronounced with age, but — unless they are extreme and persistent — they are not considered indicators of Alzheimer's or other memory-impairing illnesses.
(My personal favorite...)
3. Blocking
Someone asks you a question and the answer is right on the tip of your tongue — you know that you know it, but you just can't think of it. This is perhaps the most familiar example of blocking, the temporary inability to retrieve a memory. In many cases, the barrier is a memory similar to the one you're looking for, and you retrieve the wrong one. This competing memory is so intrusive that you can't think of the memory you want.
Scientists think that memory blocks become more common with age and that they account for the trouble older people have remembering other people's names. Research shows that people are able to retrieve about half of the blocked memories within just a minute.