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Like almost every other person over the age of 100 with whom I've spoken, Ruth McShane chuckles briefly almost every time she speaks. It's not confused laughter, more like a quick preface to her reply that seems to warn, "This sounds silly even to me, but I'm going to say it anyway."
McShane is doing her best to "pass" a battery of tests put to her by Dr. Tom Perls, M.P.H. '93, and Margery Silver, Ed.D. '82, collaborators in a study of centenarians initiated by Perls, a gerontologist at Beth Israel Hospital and director of geriatrics curriculum development at Harvard Medical School. The tests, which assess cognition, are administered by Silver in McShane's kitchen. Ten years ago, her daughter's family bought this Victorian house in a middle-class South Boston community and renovated the first floor, allowing McShane to move from a senior housing facility in Maine.
She's an extremely fortunate woman at her age, surrounded by loving relatives and living in a state of near independence with considerable privacy. Somewhat deaf, she avoids watching television, but despite failing vision enjoys reading books by Horatio Alger and Zane Grey. After breaking a hip several years ago, she began using a walker. Otherwise, there's little to distinguish her from people 20 or 30 years her junior.
While Perls tapes the kitchen-based testing scene with a camcorder, McShane listens intently as Silver, a neuropsychologist on staff at the New England Deaconess and Beth Israel hospitals, slowly reads a series of random digits. With little hesitation, McShane repeats the eight-digit sequence flawlessly. Then Silver reads an absurd story about Will Rogers and his dog, and McShane laughingly answers questions about it with virtually no mistakes. Finally, there's a page of multiplication and long division problems. McShane hesitates, seemingly stumped. As we wait, tension prickles up slightly in the small kitchen.
"I'm having trouble seeing your numbers," she says after a few minutes. The numbers are a bit faint on the page. Silver quickly takes the sheet back and retraces the figures with a marker. Mrs. McShane clears her throat with a Maine-bred ayuh, and resumes calculating. Within a few minutes, she has solved all the problems flawlessly. Her daughter informs us that McShane worked as a bookkeeper into her 80s. After a few more problems, the researchers pack up their materials and leave, with many thanks to McShane and her family.
"There's nothing clinically wrong with her," Perls says a few minutes later, outside the home. There was only one part of the assessment in which McShane had real difficulty: drawing hands on a clock's face to read ten-to-eleven. Many centenarians stumble on this one, Perls noted, suggesting that it may be an early indicator of impending mental dysfunction. Or it may just be a by-product of poor vision. But nowadays, most clocks are digital, anyway. There's no reason McShane couldn't go back to balancing the books tomorrow. "So the question we're left to grapple with," Perls says, "is what is disease and what is normal cognitive pathology at this age?"
In the same way that urinary incontinence was once thought to be part of normal old age, it was assumed that dotage and aging were synonymous. Today, we realize that these cognitive deficits result from bona fide disease: the destructive neuritic plaques and tangles of Alzheimer's disease or the oxygen-depriving brain damage caused by stroke. Depression, also pathological, can also interfere with clear thinking. It appears that healthy centenarians like Ruth McShane are not lucky aberrations, but rather what is to be expected from the human body and mind in the absence of disease. Today, researchers like Perls are focusing on a "natural history" of aging that does not necessarily include such illnesses. Although aging certainly is accompanied by change in capacity, it's not clear that age imposes illness or frailty, as has been so commonly assumed.
Several older studies have indicated that electroencephalograms (EEGs), a measure of brain electrical activity, slow down in the elderly. Slowed EEGs also appear in people with Alzheimer's disease. Many people drew the conclusion that aging and Alzheimer's disease might represent different points on a single continuum, reinforcing the notion of a close relationship between aging and Alzheimer's. Perhaps Alzheimer's was simply the cognitive decline that would take place in all of us, should we be unlucky enough to live that long.
However, research by two associate professors at Harvard Medical School, Marilyn Albert, a Massachusetts General Hospital neuropsychologist, and Dr. Frank Duffy, a Children's Hospital neurologist, bolsters the idea that Alzheimer's is not a natural part of aging. These researchers chose as their study population healthy elderly people who had been enrolled in the Boston Normative Aging Study.
"We didn't want to fall into the trap of studying sick people," Albert recalls. "We wanted to study aging, not disease."
Their studies showed that-at least in healthy adults-brain activity does not slow down, but rather speeds up. "Alzheimer's is not just a logical consequence of aging," says Albert, "and age-related changes may be quite different from those caused by Alzheimer's. There is obviously some overlap, but that overlap is what everyone focused on before; now we're focusing more on the differences."
The popular assumption is that the odds of anyone maintaining a well-burnished brain for an entire century are extremely slim. But Perls thinks that is probably a necessity for anyone to survive that long. "A few years ago, when I was a fellow at the Hebrew Rehabilitation Center for Aged," Perls recounts as we head back from Ruth McShane's house to Beth Israel, "there were two residents living there who were over 100. The amazing thing was that I never saw them because they were never on the floor. They were always off somewhere doing activities; they were very busy people. Now, this flew in the face of everything I'd learned as a medical student. We were taught that very elderly people were ill and frail and in constant need of assistance and accommodation. But I think there's a demographic selection, a 'survival-of-the-fittest' phenomenon in deciding who lives into old age. For instance, you find that on average, men in their 90s are more likely to be cognitively intact than men in their 80s. People who have lost their cognitive capacity can't make the cut; you have to be extremely smart and assertive to live to be 100."
Perls's own research lends credence to these conjectures. A study he published recently shows that, at least in the hospital setting, individuals over age 70 cost less to take care of than younger people. Perls believes that the reason is that the very elderly are actually on average healthier than the "younger elderly."
But if there's so much pressure on our genes to maximize the vim and vigor of our younger years while ignoring our post-childbearing era, if our genes really don't care about us when we're old, why are steadily increasing numbers of people surviving well into their 80s and 90s?
"It may turn out that there's some genetic pressure to age slowly," Perls says. "It certainly would confer a reproductive advantage in terms of extending the childbearing years. In fact, we've seen some centenarians who were born late in their parents' lives. One of our centenarians was born when her mother was 54."
Perls's study will aid in the demarcation of the mind's lifespan, the boundaries of which are still far from clear. Jeanne Calment, a 121-year-old French woman whom Perls refers to as "the Michael Jordan of aging," appears to remain cognitively intact, despite failed eyesight and hearing. The brain, it would appear, rejects mandatory retirement at age 65.
