Investigating medical decision-making capacity in patients with cognitive impairment using a protocol based on linguistic features

A critical question is whether cognitively impaired patients have the competence for autonomous decisions regarding participation in clinical trials. The present study aimed to investigate medical decision-making capacity by use of a Swedish linguistic instrument for medical decision-making (LIMD) in hypothetical clinical trials in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). Three comparable groups (age, education) participated in the study: AD (n=20; MMSE: 24.1 +/- 3.3) and MCI (n=22; MMSE: 26.7 +/- 2.4) patients and healthy controls (n=37; MMSE: 29.1 +/- 1.0). Medical decision-making capacity was operationalized as answers to questions regarding participation in three hypothetical clinical trials. Answers were scored regarding comprehension, evaluation and intelligibility of decisions, and a total LIMD score was used as the measure of medical decision-making ability. Groups differed significantly in LIMD with AD patients performing worst and MCI poorer than the control group. A strong association was found between all LIMD scores and diagnosis which supported the assertion that LIMD as it is designed is a one-dimensional instrument of medical decision-making capacity (MDMC). The results indicate that a fundamental communicative ability has an impact on the competence for autonomous decisions in cognitive impairment.