Superior memory and higher cortical volumes in unusually successful cognitive aging

Abstract

It is "normal" for old age to be associated with gradual decline in memory and brain mass. However, there are anecdotal reports of individuals who seem immune to age-related memory impairment, but these individuals have not been studied systematically. This study sought to establish that such cognitive SuperAgers exist and to determine if they were also resistant to age-related loss of cortical brain volume. SuperAgers were defined as individuals over age 80 with episodic memory performance at least as good as normative values for 50- to 65-year-olds. Cortical morphometry of the SuperAgers was compared to two cognitively normal cohorts: age-matched elderly and 50- to 65-year-olds. The SuperAgers' cerebral cortex was significantly thicker than their healthy age-matched peers and displayed no atrophy compared to the 50- to 65-year-old healthy group. Unexpectedly, a region of left anterior cingulate cortex was significantly thicker in the SuperAgers than in both elderly and middle-aged controls. Our findings identify cognitive and neuroanatomical features of a cohort that appears to resist average age-related changes of memory capacity and cortical volume. A better understanding of the underlying factors promoting this potential trajectory of unusually successful aging may provide insight for preventing age-related cognitive impairments or the more severe changes associated with Alzheimer's disease.

Fig. 1

Episodic memory performance and differences in cortical thickness by group. (a) Group average delayed recall scores on the RAVLT word list show SuperAgers performing significantly better than elderly controls. There is no significant difference in episodic memory performance between SuperAgers and middle-aged controls. The solid and dotted lines represent the average normative values for a 60-year-old and an 80-year-old, respectively (Schmidt, 2004). * represents significant differences at p <.05. (b) Red and yellow represent significantly thinner cortex in elderly controls compared to middle-aged controls. (c) There is no significant thinning in the SuperAging group in either hemisphere compared to middle-aged controls. A region within the anterior cingulate (blue) is significantly thicker in SuperAgers when compared to middle-aged controls. (d) Red and yellow represent significantly thinner cortex in elderly controls compared to SuperAgers. False discovery rate (FDR) was set at 0.05 for each MRI analysis. Color bars display significance using as −log(10) p value.

Fig. 2

Quantification of the left hemisphere anterior cingulate region by group. (a) Inflated medial surface of left hemisphere shows the anterior cingulate region, identified in the whole-brain group comparison (Figure 1B) as significantly thicker in SuperAgers than in middle-aged controls. (b) Boxplots of average left hemisphere anterior cingulate thickness data by group. * represents significant differences in average thickness at p <.05.