Discounting preferences and response consistency as markers of functional ability in community-dwelling older adults.

INTRODUCTION: Predictors of functional independence in older adults are in need. Based on findings that delay discounting, probability discounting, and the ability to respond consistently use cognitive abilities and neural systems with central relevance to functional ability, the present study evaluated whether these behavioral economic variables account for variance in everyday functioning in older adults. It was hypothesized that greater preference for immediate/probabilistic rewards and response inconsistency would independently predict decrements in instrumental activities of daily living (IADLs).

METHOD: Participants included 64 community-dwelling older adults (65-85 years; mean age = 76.25 years; 76.60% female). Exclusionary criteria were neurological illness, illiteracy, substance dependence within the past 5 years, score of ≤20 on the Mini-Mental State Examination, and/or presence of dementia. Delay/probability discounting tasks consisted of a series of dichotomous selections between smaller, immediate/guaranteed and larger, delayed/probabilistic monetary values. Area under the curve (AUC) was used to index levels of discounting, while response (in)consistency was based on the percentage of contradictory responses. The Direct Assessment of Functional Status-Revised (DAFS-R) provided a performance-based assessment of IADLs. Hierarchical regression analyses were conducted to determine whether discounting preferences and response consistency accounted for variance in functional ability over and above relevant demographic characteristics.

RESULTS: Demographic characteristics accounted for significance variance in IADLs (p = .001, R(2) = .237). Probability discounting AUC (p = .014, ΔR(2) = .075) and response (in)consistency (p = .046, ΔR(2) = .050) each accounted for significant additional variance in functional ability, as did delay discounting response (in)consistency (p = .010, ΔR(2) = .081). Delay discounting AUC did not add significantly to the model (p = .861).

CONCLUSIONS: Discounting preferences and choice consistency hold potential to serve as relatively fast and inexpensive markers of functional decline, likely due to neurocognitive deterioration relevant to both behavioral economic decision making and functional independence.