Reduced delayed reward selection by Alzheimer's disease and mild cognitive impairment patients during intertemporal decision-making

Intertemporal decision-making refers to selection among options with distinct consequences over time. Older adults have to make important decisions regarding health care and finances among other difficult issues with different shorter- and longer-term outcomes. Patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI), a potential harbinger of AD, may make suboptimal decisions in complex situations, possibly due to impaired capacity for temporal discounting. This study aimed to evaluate intertemporal preferences in AD and MCI patients compared to healthy matched controls. AD or MCI patients and healthy control (HC) patients participated in a computerized, Chinese version of the Intertemporal Choice Task in which they were asked to choose between sooner-smaller (SS) and later-larger (LL) options in now-trials and not-now-trials. The main evaluation parameter was the percentage of choices for delayed rewards(%LL). AD or MCI patients tended to choose SS options in now-trials and not now-trials with greater frequency compared to HC patients. Additionally, AD and MCI patients demonstrated significantly poorer performance in several cognitive tests compared to healthy groups, including the Mini Mental State Exam (MMSE) and other tests of memory, attention and executive function. Correlational analysis revealed that poor intertemporal decision-making was associated with executive function deficits in MCI patients. Reduced intertemporal decision-making capacity in MCI may stem from impaired executive function, possibly due to frontal-parietal circuit degeneration. The cognitive and neurophysiological deficits underlying reduce decision-making capacity in AD warrant further investigation.