The study collected medical histories and reviewed medical records, and discovered that among those with dementia at ages 100 or older, the subjects still markedly delayed the onset of dementia relative to the average age of onset- particularly of late onset Alzheimer's Disease.
During the first year of my geriatrics fellowship, in 1991, I was assigned numerous patients-among them were two individuals who would change my life forever. Though I gradually became acquainted with the other residents who lived in the "independently functioning" residential section of Boston's Hebrew Rehabilitation Center for Aged, I had yet to meet this section's two centenarian patients who would so influence my life and work. They were, quite simply, never around for me to meet.
I was surprised that there were centenarians residing on the Center's most independent floor because the notion of "the older you get, the sicker you get" was so ingrained in me from years of caring for older patients in the hospital. This maxim definitely did not apply to Celia Bloom, age 100, and Ed Fisher, age 101.
I finally discovered why they were never available to meet me: Celia was always busy beautifully playing Mozart and Chopin on the piano for other residents. Ed was devotedly volunteering in Occupational Therapy, teaching tailoring and clothes-mending-his trade for over eighty years. When he was not teaching, Ed was off "robbing the cradle," dating his 85-yearold girlfriend (Perls, Lauerman, and Silver, 1999).
At the time, the East Boston Study, a population- based prevalence study of Alzheimer's Disease, had recently indicated that about 50 percent of people over age 85 had Alzheimer's Disease (Evans et al., 1989). Given what appeared to be an increasing incidence of the disease with age, it seemed that all people living to age 100 should have Alzheimer's. But the two centenarians I was caring for did not have the disease and, from what I could tell, they were entirely cognitively intact. This surprised me, piqued my curiosity, and led me toward a life-changing endeavor.
Centenarians: Models of Resistance to Alzheimer's Disease
Forming this clinical observation about Celia and Ed (which appeared to counter the conventional wisdom of the time), I embarked on a new research project: to determine the prevalence of Alzheimer's Disease in a population-based sample of centenarians. I hypothesized that because Alzheimer's is associated with premature mortality, it would be unlikely that a person could live to age 100 while having developed the disease. Later, I found out that such a supposition was the basis of the idea of demographic selection. In demographic selection, as a population ages, at some point those with age-related diseases associated with increased mortality risk die off, leaving behind a cohort of healthier select survivors (Perls, 1995; Vaupel and Yashin, 1985; Vaupel et al., 1998).
Using voter registries and local newspaper articles about centenarian birthdays, I tried to find and enroll all the centenarians living in eight communities around Boston. At a prevalence rate of one centenarian per 10,000, and given a population base of 460,000, at any one time I should have been studying about forty-six centenarians: I ended up with a sample of forty-three subjects (Perls et al., 1999).
Together with Dr. Margery Silver, a neuropsychologist with expertise in aging, we determined the prevalence of dementia in this sample using Consortium to Establish a Registry for Alzheimer's Disease (CERAD) criteria. Twenty percent had no dementia, 15 percent were assigned a diagnosis of "uncertain," and the remaining 65 percent had at least some degree of dementia (Silver, Jilinskaia, and Perls, 2001). Though a dementia frequency of 65 percent was quite high, it still seemed remarkable, given their age, that about one-fifth of the centenarians were clinically cognitively intact.