Can performance on daily activities discriminate between older adults with normal cognitive function and those with mild cognitive impairment?

Abstract

To the Editor: Rodakowski et al.1 have presented important work regarding the use of cognitive instrumental activities of daily living (C-IADLs) to distinguish between older adults with normal cognitive function and those with mild cognitive impairment (MCI), and we commend them for highlighting the serious effect of MCI on the elderly. However, the authors contend that “these findings are the first to demonstrate the utility of C-IADLs for distinguishing between normal cognitive function and MCI.” This statement is misleading because this article joins a sizable body of literature that uses observed or reported C-IADLs to distinguish normal cognitive function from MCI. Both methodologies appear valid, and reported IADLs have the distinct advantage of easy application in community (nonacademic) settings. For example, the Alzheimer's Disease Cooperative Study/Activity of Daily Living Scale for individuals with MCI uses caregiver reports and can detect early changes in function between healthy controls and individuals with amnestic MCI (aMCI).2 Qualitatively, the C-IADL deficits found in that study are similar to those in the Rodakowski et al. paper and include important activities such as shopping and checkbook balancing, and two other studies directly compared observed and reported C-IADLs and showed a correlation between the two.3, 4 On closer reading, Rodakowski et al. recognize some of these other studies that corroborate their findings,5-8 but this is only mentioned in passing and may be overlooked because the abstract and concluding paragraph of the paper report the results as novel findings. In the greater context of the existing literature, the Rodakowski et al. article's use of the observation-based Performance of Self-Care Skills to measure C-IADLs and its consistency with the results of the previous article,2 serves as further validation that observed or reported methods are satisfactory for detecting MCI. Given that these studies have shown that both observed and reported methods of the C-IADL measurement can distinguish between normal cognitive function and MCI, it seems valid that in resource-poor settings the use of reported methods rather than the observation-based methods may be appropriate. Observation-based C-IADLs could be useful to minimize bias associated with reported methods such as poor recall, diminished awareness, affective states, and denial of deficits by cognitively impaired individuals and their proxies.9 However, in the case of MCI, it seems unlikely to give better information than reported methods. Another reason to use observation-based methods, which the Rodakowski et al. article did not address, is to measure the time it takes the individuals to perform the C-IADL, because individuals with MCI may be able to perform all C-IADLs but may not be able to do them in a timely manner.8 Furthermore, Rodakowski et al. mention the possibility of trained evaluators assessing shopping and checkbook balancing deficits in 10 to 15 minutes, but it is unlikely that these tasks can be observed in such a short time unless a proxy for these tasks is used such as performance-based tests such as the Everyday Problems Test.3 However, performance-based methods are not perfect either because they usually remove the role of the environment from the equation and can show wide fluctuation of results that can change depending on the individual's level of motivation, behavior, and cognition at the time the C-IADLs are measured.10 Nonetheless, the findings in the Rodakowski et al. article are an important verification of our understanding of preclinical disability and the observation-based Performance of Self-Care Skills method for measuring C-IADLs and further elucidate which IADLs are useful for detecting changes between cognitively intact individuals and those with MCI. The findings are a step in the right direction toward operationalizing the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, diagnostic criteria for mild neurocognitive disorder, but it does not seem necessary to favor observed methods over reported methods for C-IADLs to evaluate individuals suspected of having MCI. An important next step in solidifying diagnostic criteria for MCI will entail finding common ground between the various methods of measuring C-IADLs, whether they are observed or reported, and agreeing on a set instrument that can ultimately become a criterion standard for assessing MCI. This research is supported by National Institutes of Health GEMSSTAR1 R03 AG040624–01, P50 AG005138, and R01 AG029656–01A1; the American Geriatrics Society Jahnigan Scholar Program; and the Foundation for Anesthesia Education and Research. Conflict of Interest: Authors report no conflict of interest. Author Contributions: Authors contributed equally to the letter to the editor. Sponsor's Role: None.