Evidence for Different Trajectories of Delay Discounting in Older Adults With Mild Cognitive Impairment and Mild Alzheimer's Disease.

Objectives: To examine whether delay discounting (DD) develops differently within individuals diagnosed with mild cognitive impairment (MCI) or mild Alzheimer's disease (AD).

Method: We set out to study trajectories of DD in N = 111 older adults (Mage = 75.2 years, range: 55-94, 53% female) with MCI (n = 64) or mild AD (n = 47). Data were repeatedly assessed on three measurement times over a period of 2 years.

Results: Results indicated a meaningful difference in the trajectories of DD between MCI and mild AD (t = 2.99, p = .004), with AD patients displaying higher DD rates compared with MCI. Lower intelligence (t = -2.50, p = .013) was related to higher DD. We also found reward-dependent group differences in DD (small: p = .079; medium: p = .258; large: p = .007). Age, functional ability, general cognitive ability, living situation, and marital status were not meaningfully linked to DD (all non significant). Further explorative analyses revealed an increase in DD in patients whose cognitive symptoms had progressed at time 2, compared with more stable courses of mild AD or MCI (diagnosed at time 2).

Discussion: Our results point toward an increase in DD as a function of advanced cognitive decline.