Amazingly, brain cells start to deteriorate by the 30s, with the effects of this becoming more apparent by one's 40s, 50, and 60s: forgetting what you just walked in a room to get, losing your keys, blanking on a name. These are examples of normal memory loss, especially when they occur just every once in awhile. It's NOT normal memory loss for these kinds of lapses to be constant and noticeable by others,. It's probably not normal memory loss when lapses interfere with normal daily life (chronically forgetting to turn off the stove, getting lost when you go out driving, not being able to remember what you did that morning). Many different things can contibribute to memory problems, however; it's not always Alzheimer's. See this blog post about the many different kinds of memory loss. An enlightening book on normal memory loss is Where Did I Leave My Glasses? The What, When and Why of Normal Memory Loss.