Abstract
Cognitive reserve (CR) is understood as capacity to cope with challenging conditions, e.g. after brain injury or in states of brain dysfunction, or age-related cognitive decline. CR in elderly subjects has attracted much research interest, but differences between healthy older and younger subjects have not been addressed in detail hitherto. Usually, one-time standard individual assessments are used to characterise CR. Here we observe CR as individual improvement in cognitive performance (gain) in a complex testing-the-limits paradigm, the digit symbol substitution test (DSST), with 10 repeated measurements, in 140 younger (20–30 yrs) and 140 older (57–74 yrs) healthy subjects. In addition, we assessed attention, memory and executive function, and mood and personality traits as potential influence factors for CR. We found that both, younger and older subjects showed significant gains, which were significantly correlated with speed of information processing, verbal short-term memory and visual problem solving in the older group only. Gender, personality traits and mood did not significantly influence gains in either group. Surprisingly about half of the older subjects performed at the level of the younger group, suggesting that interindividual differences in CR are possibly age-independent. We propose that these findings may also be understood as indication that one-time standard individual measurements do not allow assessment of CR, and that the use of DSST in a testing-the-limits paradigm is a valuable assessment method for CR in young and elderly subjects.
Highlights
The concept of cognitive reserve (CR) has been designed to describe and explain individual differences in susceptibility to pathological changes in brain morphology in subjects suffering from traumatic brain injury [1], and in elderly subjects with brain atrophy [2,3]
Motivation-related occupational abilities [15], regular challenging cognitive activities as well as higher socioeconomic status are associated with reduced risk of mild cognitive impairment (MCI) and dementia [16]
The main outcome of this study is that both, younger and older subjects showed a significant increase in performance in the digit symbol substitution test (DSST) after systematic practice
Summary
The concept of cognitive reserve (CR) has been designed to describe and explain individual differences in susceptibility to pathological changes in brain morphology in subjects suffering from traumatic brain injury [1], and in elderly subjects with brain atrophy [2,3]. In contrast to the traditional view, cognitive performance in these elderly subjects was substantially better than expected, indicating ‘‘some people to be more resilient to brain changes than others’’ [4], p. Various factors contribute differently to CR, e.g. linguistic ability [10], educational and occupational attainment as well as leisure activities and lifelong experiences [4,11], lifestyle including cognitively demanding activities [12], dietary habits and regular physical exercise [13], and mentally beneficial activities [14]. As Satz et al [9]
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