SAVANNAH, GA— The landmark Nun Study, which followed more than 650 Catholic sisters 75 and older, has yielded invaluable postmortem, anatomical data on Alzheimer’s disease, but its ultimate value may be in what it tells us about the healthy aging brain. Although the concept of healthy aging is generating considerable scientific interest, there is a lack of consensus on what defines healthy aging, and its biological basis has yet to be determined. In the Nun Study, healthy longevity has been correlated with such factors as early-life linguistic ability and having obtained a college degree. Equally important to the aging process of the nuns who remained dementia-free, however, was a factor that is not so easily detected by modern epidemiologic methods, said Louis Cozolino, PhD, Professor of Psychology at Pepperdine University in Los Angeles, at the 19th Annual Meeting of the American Neuropsychiatric Association.

THE NEW STORY OF AGING

“The take-home message would be that there is more to healthy aging than the epidemiologists can imagine,” he told NeuroPsychiatry Reviews. “The usual finding—exercise more, do crossword puzzles, avoid French fries—all fit into a much broader picture … an examination of the evolution of the life span of the brain. The brain is a social organ shaped to serve multigenerational groups. In this context, we may be able to integrate some of the current findings and get clues concerning where to look for more.”

THE BRAIN AS A SOCIAL ORGAN

The new story of aging, noted Dr. Cozolino, begins with the idea of the brain as a social organ that should be studied in the context of relationships, adaptation, and lifelong development. “My training with neuropsychologists and neurologists was always geared toward loss and decline,” he said. “All of the input I receive from the culture is that aging is bad and to be avoided at all costs. Both of these worldviews are materialistic and individualistic. The fact that the brain is a social organ and that we are social creatures is lost in these ways of viewing reality.

“A new story of aging needs to include the ways in which we get better as we age—especially in the ways in which we can contribute to others—and that we are all connected via our attachments, psychological well-being, and how we serve to regulate each other’s internal physiology.

Tracing what he calls the “life history” of the social brain, Dr. Cozolino found that a decline in systems that are related to new learning—characterized by decreased lateral specialization and slower processing speed—is offset by gains in other functions of the brain. There is maintenance of systems involved in bonding and attachment, expert knowledge, episodic memory, and the generation of “narrative.” More importantly, according to Dr. Cozolino, growth and improvement are evident in the greater complexity of brain wave patterns and increased distribution and coordination of cortical activation, among other observations of positive neural change.

Key to Dr. Cozolino’s thesis are the concepts of social attachment, neural plasticity, and the positivity effect, which interact in the development of the healthy aging brain. “Positive affect, excitement, enthusiasm, exploratory behavior, and positive attachment are external manifestations of a brain that is vital, alive, plastic, and learning,” he emphasized. “They are simply different perspectives of the same phenomenon.”

MATERNAL GRANDMOTHERS AND OTHER PRIMARY CARETAKERS

The contribution of factors such as positivity and social attachment to healthy aging can be seen in the traditional roles played by elders—eg, housekeeping, child care, tribal leadership and mediation, storytelling, and the intergenerational transmission of knowledge and skills. The effects of these factors have implications not only for quality of life but also for enhanced survival.

Dr. Cozolino noted that the relative longevity of males and females has been found to correlate with infant caretaking. Studies of anthropoid primates have shown that species in which males are the primary caretakers have longer life spans. “This longevity factor could be tied to the salubrious effects of caretaking on those providing care to others,” he said.

Data have also emerged from a study conducted in rural Gambia, in which the presence of maternal grandmothers correlated with an increased survival rate and improved nutritional status of their daughter’s children. Postmenopausal maternal grandmothers had taller grandchildren than did maternal grandmothers who were still of childbearing age. The presence of paternal grandmothers and any male kin, including fathers, had no impact on survival or nutritional status.

The data from these studies point to the possibility that “our life histories have, in part, been shaped by the history of our social obligations,” said Dr. Cozolino. He noted that there is ample scientific evidence that explains why some aging brains remain healthy, including a number of imaging studies.

“The first study implies that taking care of infants may enhance our health and longevity, while the second suggests that the onset of menopause in human women may be tied to the importance of their contribution to the care of young children,” he said. “The findings of these studies are backed up by the scores of studies that have found positive correlations between positive social connectedness and measures of mental and physical health, as well as longevity.

“Data from imaging studies suggest that healthy brain aging correlates with gradual changes in neural network participation dedicated to a variety of tasks. The general trend is toward more inclusive participation across the hemispheres as well as up and down the neuraxis in tasks of memory, problem-solving, and social judgment,” concluded Dr. Cozolino. “While this results in slower processing in tasks where younger adults excel, it allows for deeper and broader consideration of tasks for which older adults have traditionally been responsible, such as solving social disputes, storytelling, and the maintenance and transmission of cultural wisdom.”

—Fred Balzac

Suggested Reading
Allman J, Rosin A, Kumar R, Hasenstaub A. Parenting and survival in anthropoid primates: caretakers live longer. Proc Natl Acad Sci U S A. 1998;95(12):6866-6869.
Cozolino L. The Healthy Aging Brain: Sustaining Attachment, Attaining Wisdom. New York, NY: W.W. Norton & Company; 2008, in press.
Sear R, Mace R, McGregor IA. Maternal grandmothers improve nutritional status and survival of children in rural Gambia. Proc Biol Sci. 2000;267(1453):1641-1647.
Tyas SL, Snowdon DA, Desrosiers MF, et al. Healthy ageing in the Nun Study: definition and neuropathologic correlates. Age Ageing. 2007;36(6):650-655.

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