I am asked this question all the time. There are many memory disorders and it's often difficult to understand the differences. Here's a brief overview.

Normal memory loss: Everybody's brain ages. As the connections and chemicals in the brain alter with time, many people forget things like names, keys, and what the they went in the next room for. This is pretty normal, and doesn't automatically lead to deterioration if a person is leading a brain healthy lifestyle.

Mild cognitive impairment: Problems with memory, language, or other problem solving functions are now noticeable to others but may not interfere with daily life. For example, Mom continually loses her keys and forgets your friend's names but he can still pay bills and get the shopping done. The presence of MCI often shows up on tests for the condition. It is thought that 1 in 5 people over 70 have MCI. Some develop Alzheimer's Disease and others don't.

Early stage Alzheimer's disease: In addition to pronounced memory problems (Dad can't remember what happened yesterday or major news events), there's cognitive trouble—he can't count backward by 7s, messes up planning meals or managing finances or gets lost. This condition can diagnosed through testing and a complete medical exam to rule out other problems.

Mid and late Alzheimer's disease: This always follow in progression after early-stage Alzheimer's Disease. There are no improvements known, only periods of stabilization with remediation and gradual decline.

Early-onset Alzheimer's disease: This is not to be confused with early-stage Alzheimer's, early-onset starts before age 65.

Dementia: Not a disease itself, but a set of symptoms including memory loss, cognitive problems, and other effects of deteriorating brain function. Alzheimer's disease is one type of dementia. Other types include vascular dementia (caused by tiny strokes) and Lewy Body Dementia (of which Parkinson's Disease Dementia is a subset).

Senile dementia: An old fashioned term that usually referred to what we now call Alzheimer's disease.

It is important to note that there can be other causes of memory loss, some of which may just be temporary: These include depression, stress, insomnia, alcoholism, brain tumors, medications, or many other conditions. Leading a healthy lifestyle and engaging your brain in new, varied and increasingly challenging activities is very important well in adance of experiencing any of these conditions.