They say the slow inevitable decline sets in during our early twenties. Like a rocket reaching its apogee, once the brain is fully developed there is the briefest lull, and then it’s all downhill, the last neural areas to develop being the first to start unravelling. By the time of old age, so certain are the impairments in mental processing that psychological tests are age-adjusted – “You’re slow Bob, but not for your age. For an 80-year-old you’re doing just fine.”
But wait. A team led by Theresa Harrison at the Cognitive Neurology and Alzheimer’s Disease Center at Northwestern University say they’ve identified a group of elderly individuals whose brains appear relatively immune to the physical effects of ageing.
Harrison and her colleagues identified these 12 “SuperAgers” (average age 84) by their exceptional mental performance. They outperformed 10 typical healthy older folk (average age 83) on a test that involved recalling lists of words, and they matched the performance of 14 healthy middle-aged volunteers (average age 58). The SuperAgers also matched the middle-aged on tests of naming things, attention and task switching, and identifying drawings by category.
Using a structural brain scanner, the researchers found that the SuperAgers had brains that seemed to have resisted the erosive influence of time. Whereas the typical older participants had thinner cortices and smaller average brain volumes (244mm cubed average) than the middle-aged (306mm cubed), the SuperAgers’ brain surfaces were just as thick as the middle-aged and their brain volumes (288mm cubed) not significantly different in statistical terms. Moreover, there was one brain region – the left anterior cingulate – that was actually thicker in the SuperAgers than in the middle-aged.
“These findings are remarkable,” the researchers said, “given the numerous reports that grey matter loss is a common, if not universal, part of normal ageing.”
Across the groups, brain volume correlated with episodic memory performance. Although cingulate thickness did not, Harrison’s team still think it’s interesting that this region was thicker in the SuperAgers. Relevant here is previous research showing that early protein accumulations in the cingulate region have been detected in Alzheimer patients.
This new study provides a tantalising demonstration that continuing neural decline into old age is not inevitable. Crucial now is to find out why the SuperAgers are so well preserved. It’s not known, for example, if they had larger brains and greater cognitive reserves to begin with, or if their brains have simply aged more slowly than usual. Perhaps their lifestyles will hold clues, although the obvious role of education appears not to be relevant with this group. Their time in education was no longer than the other participants and in fact only four of them went to university.
“Identifying the underlying factors that promote this trajectory of unusually successful cognitive aging may lead to novel insights for preventing age-related cognitive impairments or strategies for evading the more severe changes associated with Alzheimer’s disease,” the researchers said.
Theresa M. Harrison, Sandra Weintraub, M.-Marsel Mesulam, and Emily Rogalski1 (2012). Superior Memory and Higher Cortical Volumes in Unusually Successful Cognitive Aging. Journal of the International Neuropsychological Society DOI: 10.1017/S1355617712000847