Altered risk-aversion and risk-taking behaviour in patients with Alzheimer's disease

Normal individuals are risk averse for decisions framed as gains but risk taking for decisions framed as losses. This framing effect is supposed to be attenuated in Alzheimer's disease (AD) patients. We investigated the effects of highlighting rewards versus highlighting punishments on the risky decision-making of AD patients.

Fourteen mild to moderate AD patients (Mini-Mental Status Examination score, 11-23; Clinical Dementia Rating, 1-2) and 16 healthy volunteers were recruited for the study. Subjects completed a computerized task on risky decision-making in which mathematically equivalent dilemmas were presented in terms of opportunities to gain monetary rewards ('positive frame') or avoid suffering losses ('negative frame').

As expected, AD patients chose more risky options under the positive frame than the negative frame, contrary to the control group (Z =-2.671, P= 0.007). The normal difference in the distribution of risky choices between positively and negatively framed dilemmas was significantly reduced in the AD group after we adjusted for years of education, mean age and depression (F= 5.321, P= 0.030). Deliberation time did not differ significantly between the two groups.

These results suggest that AD patients making high-risk choices is associated with attenuated sensitivity to the emotional frames that highlight rewards or punishments, possibly reflecting altered evaluations of prospective gains and losses.