Background: A classification scheme and general set of criteria for diagnosing mild cognitive impairment (MCI) were recently proposed by a multidisciplinary group of experts who met at an international symposium on MCI. One of the proposed criteria included preserved basic activities of daily living and minimal impairment in complex instrumental activities of daily living (IADLs). Objective: To investigate whether older adults with MCI classified according to the subtypes identified by the Working Group (i.e. amnestic, single non-memory domain, and multiple domain with or without a memory component) differed from cognitively intact older adults on a variety of measures indexing IADLs and to examine how well measures of IADL predict concurrent MCI status. Methods: Two hundred and fifty community-dwelling older adults, ranging in age from 66 to 92, completed self-report measures of IADLs (Lawton and Brody IADL Scale, Scales of Independent Behaviour-Revised – SIB-R) and a measure of everyday problem solving indexing IADLs (Everyday Problems Test – EPT). Ratings of participants’ IADL functioning were also obtained from informants (e.g. spouse, adult child and friend). Results: Older adults with multiple-domain MCI demonstrated poorer IADL functioning than older adults with no cognitive impairment on the EPT and the SIB-R (both self- and informant-report versions). The multiple-domain MCI participants also demonstrated poorer IADLs than MCI participants with impairments in a single cognitive domain on the self-reported SIB-R and EPT. The single-domain MCI groups demonstrated poorer IADLs than older adults without cognitive impairment on the informant-reported SIB-R and EPT. No significant group differences were found on the Lawton and Brody IADL Scale. Using the EPT and SIB-R as predictors in a multinomial regression analysis, MCI group status was reliably predicted, but the classification rate was poor. Conclusion: Individuals with MCI demonstrated poorer IADL functioning compared to cognitively intact older adults. However, the changes in IADL functioning observed in MCI may be too subtle to be detected by certain measures, such as the Lawton and Brody IADL Scale.

Individuals with certain neurological conditions may demonstrate greater inconsistency (i.e., intraindividual variability) on cognitive tasks compared to healthy controls. Several researchers have suggested that intraindividual variability may be a behavioral marker of compromised neurobiological mechanisms associated with aging, disease, or injury. The present study sought to investigate whether intraindividual variability is associated with general nervous system compromise, or rather, with certain types of neurological disturbances by comparing healthy adults, adults with Alzheimer's disease (AD), and Parkinson's disease (PD). Participants were assessed on four separate occasions using measures of reaction time and memory. Results indicated that inconsistency was correlated with indices of severity of impairment suggesting a dose-response relationship between cognitive disturbance and intraindividual variability: the more severe the cognitive disturbance, the greater the inconsistency. However, participants with AD were more inconsistent than those with PD, with both groups being more variable than the healthy group, even when controlling for group differences in overall severity of cognitive impairment or cognitive decline. Consequently, intraindividual variability may index both the severity of cognitive impairment and the nature of the neurological disturbance.

The relationship between cognitive functioning and a performance-based measure of everyday problem-solving, the Everyday Problems Test (EPT), thought to index instrumental activities of daily living (IADL), was examined in 291 community-dwelling non-demented older adults. Performance on the EPT was found to vary according to age, cognitive status, and education. Hierarchical regression analyses revealed that, after adjusting for demographic and health variables, measures of cognitive functioning accounted for 23.6% of the variance in EPT performance. In particular, measures of global cognitive status, cognitive decline, speed of processing, executive functioning, episodic memory, and verbal ability were significant predictors of EPT performance. These findings suggest that cognitive functioning along with demographic variables are important determinants of everyday problem-solving.

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