Cognitive Correlates of Functional Abilities in Individuals with Mild Cognitive Impairment: Comparison of Questionnaire, Direct Observation, and Performance-Based Measures

Abstract

The relationship between, and the cognitive correlates of, several proxy measures of functional status were studied in a population with mild cognitive impairment (MCI). Participants were 51 individuals diagnosed with MCI and 51 cognitively healthy older adults (OA). Participants completed performance-based functional status tests and standardized neuropsychological tests, and performed eight activities of daily living (e.g., watered plants, filled medication dispenser) while under direct observation in a campus apartment. An informant interview about everyday functioning was also conducted. Compared to the OA control group, the MCI group performed more poorly on all proxy measures of everyday functioning. The informant report of instrumental activities of daily living (IADL) did not correlate with the two performance-based measures; however, both the informant-report IADL and the performance-based everyday problem-solving test correlated with the direct observation measure. After controlling for age and education, cognitive predictors did not explain a significant amount of variance in the performance-based measures; however, performance on a delayed memory task was a unique predictor for the informant-report IADL, and processing speed predicted unique variance for the direct observation score. These findings indicate that differing methods for evaluating functional status are not assessing completely overlapping aspects of everyday functioning in the MCI population.

Keywords:

• Activities of daily living
• Cognitive predictors
• Functional status
• Aging
• Instrumental activities of daily living
• Everyday functioning.

Acknowledgments

Maureen Schmitter-Edgecombe, Ph.D., and Carolyn M. Parsey, M.S., Department of Psychology, Washington State University, Pullman, Washington. This study was partially supported by grants from the Life Science Discovery Fund of Washington State; the National Institutes of Biomedical Imaging and Bioengineering (Grant #R01 EB009675); and National Science Foundation (Grant DGE-0900781). No conflicts of interest exist. We thank Chad Sanders, Alyssa Weakley, and Jennifer Walker for their assistance in coordinating data collection. We also thank members of the Aging and Dementia laboratory for their help in collecting and scoring the data.

Notes

¹ Because of the limited sample size, regression analyses were also run without entering age and education in the first step. The pattern of data was nearly identical. Similarly, the findings revealed that the cognitive predictors did not account for significant variance in the OTDL-R, R² = .22, F(5, 42) = 2.32, p = .06, but did account for significant variance in the informant-report IADL, R² = .36, F(5, 37) = 4.11, p = .005, and the direct observation score, R² = .56, F(5, 42) = 10.56, p < .001. Again, the memory measure (MAS delayed list recall) emerged as the only unique predictor for the informant-report measure, B = –.38, t = –2.68, p = .01, and the processing speed measure (SDMT-oral) emerged as the only unique predictor for the direct observation score, B = –.65, t = –4.99, p < .001, and for the EPT, B = .36, t = 2.04, p = .049. The one exception was for the EPT where the cognitive predictors just reached significance, R² = .26, F(5, 37) = 2.61, p = .04.