Dementia: is it really a disease?

So is Alzheimer's-type dementia really a disease?

Prevalence of Alzheimer’s Rises 10% in 5 Years - New York Times:

... The updated estimates, based on the rising occurrences of the disease with age, not new disease research, were released yesterday by the Alzheimer’s Association, along with a compilation of other information about a progressive brain disease that afflicts 13 percent, or one in eight people 65 and over, and 42 percent of those past 85...

...Mary Mittelman, an Alzheimer’s researcher at New York University, had mixed feelings about disproportionate attention to early onset Alzheimer’s disease. On the one hand, Dr. Mittelman said, these cases are such a small minority that she fears will take focus and resources “from the majority who are much older.” On the other, she said, 'because of the ageism of this society” far too many people still believe dementia to be part of normal aging and attention to this younger group will clarify that it is a 'real disease'.”

When 42% of people over 85 have advanced features of a prolonged process, is this a "real disease" or an aging process? The boundary here is pretty fuzzy. Nobody has the brain or body at 85 that they had at 45, much less 25.

My personal bias is that the "Alzheimer's process" is a "normal" part of aging, right up there with getting weak, flabby, and shorter. What varies, of course, is how fast it progresses, and whether one dies before or after the process becomes disabling (disability also being a fuzzy term -- many persons who we consider "able" at 85 are unable to do the work they did at 45).

The distinction between an aging process and a disease has a practical implication. In general, diseases are treatable, but aging is much harder to stop. If we accpet the model of an Alzheimer's "Process" rather than Alzheimer's Disease, then we can better judge how great our challenge is. We need to do more than arrest a disease, we need to slow the aging process of the human brain. The bright side is that there's been a lot of research lately that suggests that might be possible.