SIMPLIFYING DETECTION OF MILD COGNITIVE IMPAIRMENT SUBTYPES

Evaluating the Real-World Representativeness of Participants with Mild Cognitive Impairment in Canadian Research Protocols: a Comparison of the Characteristics of a Memory Clinic Patients and Research Samples

Background

Studies of mild cognitive impairment (MCI) employ rigorous eligibility criteria, resulting in sampling that may not be representative of the broader clinical population.

Objective

To compare the characteristics of MCI patients in a Calgary memory clinic to those of MCI participants in published Canadian studies.

Methods

Clinic participants included 555 MCI patients from the PROspective Registry of Persons with Memory SyMPToms (PROMPT) registry in Calgary. Research participants included 4,981 individuals with MCI pooled from a systematic literature review of 112 original, English-language peer-reviewed Canadian studies. Both samples were compared on baseline sociodemographic variables, medical and psychiatric comorbidities, and cognitive performance for MCI due to Alzheimer’s disease and Parkinson’s disease.

Results

Overall, clinic patients tended to be younger, more often male, and more educated than research participants. Psychiatric disorders, traumatic brain injury, and sensory impairment were commonplace in PROMPT (up to 83% affected) but > 80% studies in the systematic review excluded these conditions. PROMPT patients also performed worse on global cognition measures than did research participants.

Conclusion

Stringent eligibility criteria in Canadian research studies excluded a considerable subset of MCI patients with comorbid medical or psychiatric conditions. This exclusion may contribute to differences in cognitive performance and outcomes compared to real-world clinical samples.

Apolipoprotein E4 Allele and Gait Performance in Mild Cognitive Impairment: Results From the Gait and Brain Study

Background

The apolipoprotein E polymorphism ε4 allele (ApoE4) and gait impairment are both known risk factors for developing cognitive decline and dementia. However, it is unclear the interrelationship between these factors, particularly among older adults with mild cognitive impairment (MCI) who are considered as prodromal for Alzheimer's disease. This study aimed to determine whether ApoE4 carrier individuals with MCI may experience greater impairment in gait performance.

Methods

Fifty-six older adults with MCI from the "Gait and Brain Study" who were identified as either ApoE4 carriers (n = 20) or non-ApoE4 carriers (n = 36) with 1 year of follow-up were included. Gait variability, the main outcome variable, was assessed as stride time variability with an electronic walkway. Additional gait variables and cognitive performance (mini-mental state examination [MMSE] and Montreal Cognitive Assessment [MoCA]) were also recorded. Covariates included age, sex, education level, body mass index, and number of comorbidities.

Results

Baseline characteristics were similar for both groups. Repeated measures analysis of covariance showed that gait stride time and stride length variabilities significantly increased in ApoE4 carriers but was maintained in the non-ApoE4 carriers. Similarly, ApoE4 carriers showed greater decrease in MMSE score at follow-up.

Conclusions

In this sample of older adults with MCI, the presence of at least one copy of ApoE4 was associated with the development of both increased gait variability and cognitive decline during 1 year of follow-up. ApoE4 genotype might be considered as a potential mediator of decline in mobility function in MCI; future studies with larger samples are needed to confirm our preliminary findings.

Limitations for interpreting failure on individual subtests of the Montreal Cognitive Assessment

BACKGROUND

The Montreal Cognitive Assessment (MoCA) is sensitive to mild forms of cognitive impairment in geriatric populations and asks questions under the subheadings visuospatial/executive, naming, attention, language, abstraction, delayed recall, and orientation. This study examined the extent to which these subsets of MoCA items evaluate their intended cognitive domains.

METHODS

Clinical data from 185 geriatric memory clinic outpatients who underwent cognitive screening and subsequent neuropsychological assessment were analyzed. Factor analysis of their neuropsychological test scores identified 5 cognitive domains memory, language, visuospatial ability, attention/processing speed, and cognitive control. Scores on MoCA subtests were examined for their correlations with individual factor scores and for their sensitivity and specificity in predicting impairment within each domain.

RESULTS

The MoCA subtest scores correlated significantly but modestly with neuropsychological test factor scores in their corresponding domains, for example, the correlation between 5-word recall and the memory factor was 0.46. However, subtest scores were poor predictors of impaired performance on the tests contributing to each cognitive domain. The best predictive accuracy was seen for the visuospatial/executive subtest that showed fair accuracy at predicting impairment on tests in the visuospatial domain. Other subtests showed unacceptably poor levels of accuracy when predicting impaired scores in their respective domains (60%-67%).

CONCLUSIONS

In a sample of geriatric outpatients referred for cognitive assessment, performance on individual items and subtests of the MoCA yields insufficient information to draw conclusions about impairment in specific cognitive domains as determined by neuropsychological testing.

Development of a method for quantifying cognitive ability in the elderly through adaptive test administration

BACKGROUND

The field of geriatric medicine has identified a need for an evaluative tool that can rapidly quantify global cognitive ability and accurately monitor change over time in patients with a wide range of impairments. We hypothesized that the development of an adaptive test approach to cognitive measurement would help to meet that need. This study aimed to provide evidence for the interpretability of scores obtained from a novel, adaptive approach to cognitive assessment, called the Geriatric Rapid Adaptive Cognitive Estimate (GRACE) method.

METHODS

An adaptive method for cognitive assessment was developed using data from 185 patients referred for geriatric cognitive assessment, and pilot tested in an additional 137 patients. Correlations between test scores and between rank orders of patients were computed to examine the reliability and validity of cognitive ability scores obtained by (1) administering test questions out of their usual order, (2) administering only a subset of questions, and (3) administering questions adaptively using simplified selection rules based on the most difficult question passed.

RESULTS

Cognitive ability scores obtained with the GRACE method correlated highly with the Montreal Cognitive Assessment (MoCA) scores (r = 0.93) and ranked patients similarly in order of ability (r > 0.87). A simplified adaptive testing algorithm for pencil-and-paper assessment demonstrated moderately high correlations with scores obtained from administering the full set of MMSE and MoCA items as well as the MoCA items alone.

CONCLUSIONS

Scores from the GRACE method can be obtained easily in 5-10 minutes, reducing test burden. The resulting numeric score quantifies cognitive ability, allowing clinicians to compare patients and monitor change in global cognition over time. The adaptive nature of this method allows for evaluation of persons across a broader range of cognitive ability levels than currently available tests.