Core idea

These researchers found that the performance on a series of cognitive tests could predict whether an older adult would be alive after four years.  Individuals who died had performed poorly (four years previously) at baseline on several cognitive tests compared to their peers who remained alive.  However, the reason why poorer cognition was linked to death remains a mystery.

What they say

Researchers examined 796 community dwelling older adults ages 65 years and older.  Participants were interviewed by a research nurse who administered the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).  RBANS is a brief, individually administered screening test that measures several cognitive domains and consists of 12 subtests (List Learning, Story Memory, Figure Copy, Line Orientation, Picture Naming, Semantic Fluency, Digit Span, Coding, List Recall, List Recognition, Story Recall, and Figure Recall) and five index scores (Immediate memory, Visuospatial/Constructional, Language, Attention, and Delayed Memory).

Of the 796 who participated in the study, 98 individuals died and 698 remained alive at the four-year follow-up.  Individuals who survived were younger and more likely to be female and had fewer medical conditions than individuals who died. The group that lived differed from the group that died on a number of baseline measures of cognitive functioning from the RBANS, including List Learning, Line Orientation, Semantic Fluency, Coding, List Recall, List Recognition, Story Recall, and Figure Recall.  On each of the subtests, individuals who survived performed better than those who did not survive. However, in an analysis including demographic and biomedical factors, the Coding subtest of the RBANS was a significant predictor of death.  Individuals that died had RBANS Coding score that were 5% lower than individuals who did not die.  It should be noted that the contribution of cognitive functioning was relatively small compared to other variables (demographic and biomedical) that were measured in the study; however, cognitive functioning did make an independent contribution in predicting mortality.   

What it means

Some researchers speculate that impaired cognition could indicate brain illness, nonbrain pathologies, or other organ dysfunction, all of which could affect survival. Also, poor cognitive functioning may be linked to early death because it may lead to poor medical adherence of self-care by way of lack of concentration, confusion, and forgetting one’s medical regimen. Better cognitive functioning has been found to be associated with better health behaviors. Better executive functioning has been found to predict problem-focused coping.  Problem focused coping could affect adjustment to health outcomes in older adults and thus predict survival.

One limitation of the study is that there was no information on cause of death.  The researchers state that it is possible that cognitive test performances might be better at predicting some causes of death (e.g., chronic and progressive illness), but poorer at predicting other causes of death (e.g., accidents, iatrogenic illnesses). The researchers mention one clinical implication, which is that older adult patients could be screened for attention capacities, such as those used in the Coding subtest of the RBANS.  More impaired individuals should be more closely monitored for greater risk of death. Also, several studies report that cognitive training has long-term positive effects on cognitive abilities and future studies need to test the effects of cognitive training on health and survival of older adults. 

References

Duff, K, Mold, J.W., & Gidron, Y. (2008). “Cognitive functioning predicts survival in the elderly.” Journal of Clinical and Experimental Neuropsychology, iFirst, 1-6.