This study lends further evidence that familial longevity is associated with better cognitive function in the offspring generation. The tendency toward better performance on tests of attention and executive function in this relatively young, small sample suggests the need for further evaluation of neuropsychological test performance, both on data already collected and over longitudinal follow-up. Preservation of cognitive function has substantial public health implications as the population is living longer than ever before. Increased average life
expectancy that is associated with more years of physical and cognitive
functional disability would have negative ramifications of greater health care and social support costs. However, increased longevity associated with preserved physical and cognitive function fitting the compression of disability paradigm would result in a population that is able to maintain independence and greater life satisfaction.
Successful cognitive aging paradigms are varied. Rowe and Kahn suggest that successful aging is a result of minimal change in function with increasing age (Rowe & Kahn, 1997). As this was not a longitudinal study, cognitive trajectories, and therefore, maintenance of cognitive function with increasing age, cannot be assessed. Although comparisons were not made between the proband generation and the offspring generation in this study, proband generation performance on average was lower than in the offspring generation. It is possible that some individuals in the proband generation are
performing in the average range of the offspring generation and are therefore successful cognitive agers. Alternatively, another definition of successful
cognitive aging is performance well above that of age-matched controls, although this definition excludes those who maintain cognitive function at average levels (Daffner, 2010). In this study, the proband generation participants did not perform significantly better than age-matched controls, and thus, would not be considered successful cognitive agers according to this definition. As cognitive function is highly correlated with mortality and both proband generation
participants and proband referents have achieved exceptional survival beyond average life expectancy and were able to take part in the study, they are all successful cognitive agers at least to some degree. However, these two cohorts may be using different pathways to achieve successful cognitive aging.
The role of education and cognitive reserve in relation to cognitive
performance in the proband generation has useful implications for people without familial longevity. Preservation of cognitive function and compression of
cognitive disability has been demonstrated with increasing exceptional longevity. In this study, proband generation participants with an average age of 91
performed similarly to the referent group regardless of the fact that those with familial longevity had lower education. This suggests that higher education and intellectual ability may give people without familial longevity similar cognitive benefits as those with familial longevity. Furthermore, the higher engagement of the proband referent group in cognitively stimulating activities, which has been
shown to be related to increased cognitive reserve, suggests that leisure
activities may also help those without familial longevity become successful agers. It has been suggested that participation in cognitively stimulating activities and physical activities provides the most evidence for increasing cognitive reserve and decreasing risk of dementia (Daffner, 2010). However, we did not find evidence of an association of current or mid-life exercise with cognitive performance in this study.
Future studies should analyze qualitative aspects of test performance, particularly in the proband generation. The tests that were administered in this battery were chosen for both their quantitative and qualitative value. Therefore, there is a significant amount of qualitative information about the process used to come to an answer that can be gleaned from these tests. More efficient
processes in performing neuropsychological tests may be indicative of the use of different neural networks. Many qualitative processes can reveal information about executive functioning that is generally not testable by direct means. Self- monitoring, the process of double-checking performance and making corrections throughout completion of a task, can lead to improved neuropsychological test performance. Similarly, clustering of words by semantic category on the word list learning tasks or verbal fluency tasks has been related to better test
performance. It is possible that although the proband generation participants had lower intellectual ability, they may be using more efficient processes to complete
tasks, and therefore, maintain cognitive function levels comparable to those with higher intellectual ability.
As stated earlier, future studies should investigate the change in cognitive function over time in this cohort with exceptional familial longevity. Cognitive trajectories as the cohort ages, particularly in the relatively young offspring generation, may reveal a divergence in cognitive performance if the offspring generation maintains cognitive stability and the referent group declines. In the proband generation, following participants over time may reveal important information about the phenomenon of terminal decline, the ability to maintain function at a high level followed by a rapid decline at the very end of life. As terminal decline is congruent with the compression of disability hypothesis, it is important to examine whether LLFS participants are able to show preservation of cognitive function until the very end of life compared with participants without familial longevity.
A continuation of the analysis of proxies of cognitive reserve is warranted due to the findings of higher participation in cognitively stimulating activities in the proband referent cohort. Additional analyses could investigate the relationship between specific types of leisure activities and cognitive performance. Creative activities or detail-oriented activities may show better association with
neuropsychological test scores than other activities. Length of duration of participation in each activity and mastery of the activity may also be related to increased cognitive performance.
One could also use the data from the neuropsychological test battery to select families with clustering for exceptional cognitive performance. Families with multiple family members scoring well above the mean across multiple tests within the battery may represent a subsample with unique genetic or
environmental contributions to cognitive performance. In addition, families with discordant siblings, one scoring well above the mean and one well below the mean could be informative for determining factors associated with successful cognitive aging.