Approximately 20 years ago, I was struck by an obituary in the New York Times reporting that the renowned mystery writer Ross MacDonald had died of Alzheimer's disease (AD). That disclosure was remarkable to me because it reflected a new public appreciation of the importance of AD as a major cause of serious morbidity and mortality. Previously, AD had not been recognized on lists of causes of deaths. Today it is recognized as the eighth leading cause of death in the United States. Affecting an estimated 4.5 million people, AD also carries the staggering economic impact of $100 billion, as observed by Dr Jody Corey-Bloom in this issue of Continuum, which is devoted to the subject of dementia. With AD responsible for 50% to 80% of cases of dementia and with the old old representing the fastest growing segment of the population, AD has clearly emerged as one of our most critical public health problems.
We have reasons to be optimistic, as the comprehensive discussions in this issue of Continuum will illustrate, because considerable progress has been made in recent years in our understanding of dementing illness. Dr Petersen has not only ably chaired the faculty for this issue but has provided a thorough analysis of the concept of mild cognitive impairment. This condition, very often a prelude to indisputable AD, is potentially an ideal target for therapeutic intervention. Dr Corey-Bloom's explication of the developments in our understanding of the pathology, neurochemistry, and genetics of AD demonstrates how far we have come in the last few decades. If efforts to interfere with amyloid deposition prove successful, such therapies will mark a dramatic triumph for the concept of translational research in which discoveries at the laboratory bench ultimately find their way to successful application at the bedside.
In recent years our understanding of the degenerative dementias has begun to turn lumpers into splitters. Drs Graff-Radford and Woodruff and Dr Boeve, respectively, analyze the relatively recently characterized entities of frontotemporal dementia and dementia with Lewy bodies. While these syndromes, like AD, currently lack effective disease-modifying therapy, better recognition of their clinical phenomenology will enable clinicians to design trials that address them specifically. In the interim, understanding the behavioral manifestations of the syndromes will permit better clinical management with both pharmacologic and nonpharmacologic modalities.
The role of vascular disease as a cause of dementia has undergone a metamorphosis. We have finally established that most cases of dementia in older adults are not a result of "hardening of the arteries" as so many of our patients were told not so long ago. Nonetheless, as Dr Knopman reviews, vascular disease is, indeed, an important cause and contributor to dementia, and he clarifies the variety of ways in which this happens. Ultimately, the solution to vascular dementia will undoubtedly lie in our ability to prevent stroke itself or to act quickly to reverse an ischemic episode.
Finally in this issue, Dr Caselli provides a discussion of other causes of encephalopathy, emphasizing for us the distinction between delirium or acute confusional states and dementia. The differential diagnosis of such patients is complex, and he leads us through a logical approach to the problem. Despite the differences between delirium and dementia, overlap occurs, and neurologists often must sort out the problem for primary care physicians and our colleagues in other specialties.
This issue of Continuum marks an exciting milestone for the American Academy of Neurology, as it is the first issue that residents and fellows will receive as part of a subscription provided as a perquisite of junior membership. We are proud to have the opportunity to make a significant contribution to the education of our future neurologists, as well as to foster the continuing education of those fully trained clinicians who have recognized, as endorsed by the American Board of Psychiatry and Neurology, that Continuum is "part of a comprehensive lifelong learning program, which is mandated by the ABMS as a necessary component of maintenance of certification." I can think of no more important subject than dementia to kick off this new venture for Continuum, and I am indebted to Dr Petersen and his talented faculty for an outstanding issue.
Aaron E. Miller, MD