While both groups had significant whole-brain cortical volume loss over 18 months, the annual percent change (APC) was significantly greater in the cognitively average elderly compared with SuperAgers (2.24% versus 1.06%, P=0.02), Amanda Cook, MA, of Northwestern University in Chicago, and colleagues reported in a research letter in the Journal of the American Medical Association.
"Our study found that while the brain cortex of both SuperAgers and their cognitively average peers showed shrinkage over 18 months, the rate of cortical brain atrophy in the adult controls was about double that of the SuperAgers," Cook told MedPage Today in an email.
While the effects of this observation are difficult to surmise, differences of this magnitude may have functional consequences, given that this rate of change is similar to that seen in previous studies between non-demented and demented adults over age 50 (e.g., range of APC differences of 0.5%-1.9%), the researchers said.
The study "demonstrates with a specific example that chronological age and biological age are not the same," Nir Barzilai, MD, director of the Albert Einstein College of Medicine Institute for Aging Research, who was not involved in the study, told MedPage Today in an email.
SuperAgers had significantly higher category fluency at the first visit and episodic memory scores at both visits compared with cognitively average elderly adults, Cook said. There were no other significant differences between groups in demographic or neuropsychological measures, including estimated premorbid intelligence and between-visit interval.
Cook cautioned that the possibility that SuperAgers had bigger brains in midlife cannot be ruled out, "as we do not know what their brains looked like 30+ years ago." Previous research by her group showed that at a single time point, the cortex of the SuperAgers was bigger than that of their same-age peers with average memory ability for their age.
She said her study is "relevant in the context of our aging population. Modern medicine has extended the average human life span. However, increasing age is often accompanied by 'typical' cognitive decline or, in some cases ... dementia. SuperAgers suggest that age-related cognitive decline is not inevitable."
While biological health was not assessed in this study, research from the Northwestern University SuperAging Program has not yet found differences between SuperAgers and their cognitively average peers on aspects of physical health (such as diabetes and obesity) or various health behaviors (such as diet, exercise, smoking history, and drinking habits), Cook said.
"Anecdotally, we have SuperAgers who arrive for their study visits with walkers and wheelchairs so their superior cognitive abilities do not necessarily translate into superior physical health," she added.
Cook agreed with Barzilai that more research on this population is needed: "By studying what makes SuperAgers unique, we hope to undercover biological factors, such as the reduced cortical brain atrophy demonstrated here, that may contribute to the maintenance of memory ability in advanced age."
The authors disclosed no financial conflicts of interest.
Journal of the American Medical AssociationSource Reference:
Cook AH, et al "Rates of cortical atrophy in adults 80 years and older with superior vs average episodic memory" JAMA 2017; DOI: 10.1001/jama.2017.0627.