DEAR DOCTOR K:

I am in my mid-60s, and I'm worried I might be getting more forgetful than normal for my age. I function fairly well most of the time. But sometimes I'll forget something like the details of a phone conversation I recently had. How can I know what's normal?

DEAR READER:

You sometimes forget things you didn't used to forget? Well, join the club. Each of us has more difficulty remembering things as we get older -- it's a normal part of aging. Like thinning hair and stiffer joints, subtle memory problems are common.

We used to think that there were two conditions to distinguish: the normal memory problems of aging versus dementia. We now know that there is also a middle ground of weakened mental function. By this I mean a state that's worse than normal age-related problems, but not as bad as dementia from Alzheimer's disease or other brain diseases. This in-between state is called "mild cognitive impairment."

Fortunately, mild cognitive impairment stays mild in many cases. Nevertheless, a person with mild cognitive impairment is about three times more likely to develop full-blown dementia than those without it. It is a risk factor for developing dementia and may be a stage on the road to dementia. Fortunately, many people who get to that stage don't keep heading down the road to full dementia.

People with mild cognitive impairment are able to handle the tasks of day-to-day living. They may be less efficient than they used to be, but they can live independently.

It surely does not sound like you have dementia. If you are not having trouble managing activities like shopping, preparing meals and paying bills, dementia is unlikely.

So the question is whether your memory problems are just normal aging or something else. Mild cognitive impairment is one possibility, but not the only one. Memory problems can also come from something other than a brain disorder. If a patient of mine is having serious memory problems, I consider other possible causes. These include depression, side effects from medications, thyroid problems, low vitamin B12, among others. Diagnosing and treating these conditions can fix the memory problems.

If you don't have one of these conditions, the next question is whether you have mild cognitive impairment. Your doctor may be able to get a sense of your memory and cognitive shortcomings just by speaking with you. He or she may also ask brief, standardized sets of questions to assess your weak areas. The doctor also may talk to your family and friends about their perceptions of your mental function.

Right now, the best tests for mild cognitive impairment and dementia are tests of thinking and memory performed by neuropsychologists. New brain-imaging techniques, blood and spinal fluid tests are also under development.

I predict that in the next 10 years we will develop much better tests for determining if a person has mild cognitive impairment. I think we will also develop better tests for determining the risk that a person with mild cognitive impairment will go on to develop dementia. Finally, I am hopeful that treatments may be developed that slow or prevent dementia when someone is found to be at increased risk for someday getting it.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.AskDoctorK.com.)

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