Association of cognition with temporal discounting in community based older persons

Abstract

BackgroundThe objective of this study was to test the hypothesis that cognitive function is negatively associated with temporal discounting in old age.MethodsParticipants were 388 community-dwelling older persons without dementia from the Rush Memory and Aging Project, an ongoing longitudinal epidemiologic study of aging in the Chicago metropolitan area. Temporal discounting was measured using standard questions in which participants were asked to choose between an immediate, smaller payment and a delayed, larger one. Cognition was measured using a detailed battery including 19 tests. The association between cognition and temporal discounting was examined via mixed models adjusted for age, sex, education, income, and the number of chronic medical conditions.ResultsDescriptive data revealed a consistent pattern whereby older persons with lower cognitive function were more likely to discount greater but delayed rewards compared to those with higher cognitive function. Further, in a mixed effect model adjusted for age, sex, education, income, and chronic medical conditions, global cognitive function was negatively associated with temporal discounting (estimate = −0.45, SE = 0.18, p = 0.015), such that a person with lower cognition exhibited greater discounting. Finally, in subsequent models examining domain specific associations, perceptual speed and visuospatial abilities were associated with temporal discounting, but episodic memory, semantic memory and working memory were not.ConclusionAmong older persons without dementia, a lower level of cognitive function is associated with greater temporal discounting. These findings have implications regarding the ability of older persons to make decisions that involve delayed rewards but maximize well-being.

Discrepancies between cognition and decision making in older adults

“…An example of an item is “Would you prefer $1000 in cash right now or $3000 in a year?” All immediate rewards were $1000 and delayed rewards ranged in value from $1200 to $3000. Our group has shown that temporal discounting is associated with cognition [42] and increased mortality among older adults [43]. Risk aversion (gamma) was assessed with a series of 10 coin toss questions “Would you prefer $15 for sure, OR a coin toss in which you will get $ (an amount greater than $15) if you flip heads or nothing if you flip tails?” [44].…”

Ventromedial PFC, parahippocampal, and cerebellar connectivity are associated with temporal discounting in old age

“…Temporal discounting was assessed using 7 binary questions, following a standard preference elicitation protocol, as described in detail previously (Boyle et al, 2012). Participants were asked to choose between an immediate, smaller or a delayed, larger payment.…”

“…The approach to determining temporal discounting has been detailed in prior work (Boyle et al, 2012). Briefly, the discounting factor α was estimated using an established hyperbolic function (Laibson, 1997; Frederick et al, 2002; Kirby et al, 1999; Kirby, 1997): $$V=\frac{A}{1+\alpha D}$$ where V represents the magnitude of the discounted value of the future reward A at delay D. Larger values of V correspond to smaller values of α.…”

“…Further, because there are different ways of estimating discounting, an exponential function that generates k-values was used as a comparison (Boyle et al, 2012). The correlation between the α and k values was 0.99 (p<0.001), suggesting both yield comparable measures of discounting.…”

“…Age, education, and sex are factors known to correlate with multiple outcomes in epidemiologic studies. Results were also adjusted for global cognition as this has been associated with temporal discounting (Boyle et al, 2012). Seed-based functional connectivity analysis was conducted with Resting-State fMRI Data Analysis Toolkit (REST: http://restfmri.net/forum/REST).…”