Delay and probability discounting as candidate markers for dementia: an initial investigation

Abstract

The present study investigated delay discounting and probability discounting-behavioral economic indices of impulsivity and risk proneness, respectively-in 39 healthy older adults and 25 older adults with mild cognitive impairment (MCI). Relative to the healthy group, it was hypothesized that older adults with MCI would display greater levels of impulsivity, risk proneness, and response inconsistency. The MCI group was found to display a unique delay discounting profile characterized by increasing impulsivity with decreasing reward magnitude, such that cognitively impaired older adults were significantly more impulsive than healthy controls at the small reward magnitude. The two groups exhibited similar levels of probability discounting, though older adults with MCI were significantly less consistent in their risk preferences. The present findings shed light onto decision-making in pre-dementia disease stages and suggest that discounting performance holds potential to complement early diagnostic instruments, likely due to pathophysiological processes in relevant brain regions.

Keywords: Aging; Behavioral economics; Cognition; Delay discounting; Mild cognitive impairment; Probability discounting.

Fig. 1.

Delay discounting k values by group and reward magnitude. The above figure plots estimated marginal means adjusted for educational attainment (i.e., years of formal education) and estimated premorbid intellectual ability. Older adults with MCI displayed significantly higher levels of impulsivity with decreasing reward magnitude, excluding a non-significant difference between large and medium magnitudes. The MCI group was significantly more impulsive than unimpaired older adults at the small reward magnitude with the covariates in the model.