For the first time since 1984 there is a new clinical diagnostic criteria for Alzheimer's disease dementia. Published on April 19, 2011 in Alzheimer's & Dementia, the National Institute on Aging working with the Alzheimer's Association have expanded what we now consider dementia.
While the previous guidelines only recognized one stage—Alzheimer’s dementia—the new guidelines propose that Alzheimer’s disease progresses on a continuum with three stages—an early, preclinical stage with no symptoms; a middle stage of mild cognitive impairment (MCI); and a final stage of Alzheimer’s dementia.
These new guidelines forge a solid causal link. What was before just a probability of association is now seen as a causal progression from changes in the brain that have no symptoms, to mild problems with thinking and memory and ending with dementia.
What made this possible is the introduction of new tests that can measure the health of the brain while the person is still alive. In the past, the only way to get a definitive prognosis of dementia was through an autopsy. Nowadays, especially with functional magnetic resonance imagery, the use of biomarkers makes it possible to measure changes in the brain before any symptoms appear, hence the new guidelines.
This ushers in a new era of fatalism. Unintentionally, these new guidelines are stoking the fear of dementia. A MetLife Foundation study in 2010 reported that people over 55 dread getting Alzheimer’s more than any other disease--other than cancer. These new guidelines raises our sensitivity to subtler decline in thinking and memory. However it is important to stress that this linear connection is not as clear-cut as neuroscientists would have us admit.
MCI indicate difficulty with memory and thinking that are not normal but still allow the individual to function independently. Many--but not all--people with MCI progress to Alzheimer’s dementia. However there are some important causes of MCI other than dementia--which the guidelines do not address--including medications, stroke or depression.
There are other inconsistencies in the logic of this causal path. As far back as thirty years ago M Marcel Mesulam with Northwestern University, reported 6 patients with progressive word-finding and naming difficulties that worsened over the years, but who did not develop a more generalized dementia. Even if the connection between MCI and dementia is established, Mike Martin and his colleagues from Zurich, reported the results from their meta-analysis and concluded that cognitive interventions do lead to modest performance gains with older adults.
Even if the brain has the neuropathology it does not dictate the behavior. In the famous "Nuns Study" David Snowdon first reported this very strange anomaly. He found that a third of the nuns who behaved and acted free from dementia, were found to have the disease of Alzheimer’s during autopsy. Numerous studies have also found this lack of correlation between the disease and the behavior. More recently, Archana Balasubramanian with colleagues at UCLA reported that for 58 individuals, 90 years and older--who did not have any signs of dementia during three years prior to their death--at autopsy had evidence of the disease of dementia. All these studies erode the direct linear link between the disease and the behavior. There seems to be other mediating and moderating factors that the NIA guidelines need to address, while there is a confusion of diagnosis and prognosis.
© USA Copyrighted 2013 Mario D. Garrett