Introduction: Although the hallmark feature of essential tremor (ET) is tremor, there is growing appreciation that cognitive impairment also occurs, including increased prevalence of mild cognitive impairment (MCI) and increased prevalence and incidence of dementia. With emerging knowledge of ET-cognitive impairment, come fundamental questions regarding its course, bases, predictors and clinical outcomes. Studies in the general population and in Parkinson's disease (PD), a related movement disorder, offer a starting point from which to begin filling these clinically important knowledge gaps. Methods: A PubMed search (June 2018) identified articles for this review. Results: Much of our knowledge of cognitive impairment in ET is of the static condition (e.g., prevalence of cognitive impairment in ET), with nearly no information on its bases, predictors and dynamics (i.e., course, and clinical outcomes). In PD, where such data have been published, rates of cognitive decline and conversion to MCI/dementia are higher than in the general population. Predictors of cognitive change in PD and the general population have also been identified, yet they only partially overlap one another.

Background: The utility of subjective cognitive decline (SCD) as an indicator of preclinical AD is overshadowed by its inconsistent association with objective cognition. Objective: This study examines if manipulations of SCD measurement affect its association with early cognitive dysfunction characteristic of preclinical AD. Methods: Cognitively healthy older adults (n = 110) completed SCD questionnaires that elicited complaints in general, compared to 5 years ago (retrospective SCD) and compared to their peers (age-anchored SCD) in binary and Likert scales. Outcome cognitive tasks included an associative memory task (Face-Name Test), a visual short-term memory binding task (STMB test), and a clinical neuropsychological list learning test (Selective Reminder Test). Results: SCD complaints, when compared to age-matched peers (age-anchored SCD) was endorsed less frequently than complaints compared to 5 years ago (retrospective SCD) (p <  0.01). In demographically adjusted regressions, age-anchored ordinal-rated SCD was associated with short term memory binding (β= –0.22, p = 0.040, CI = –0.45, –0.01), associative memory (β= –0.26, p = 0.018, CI = –0.45, –0.06), and list learning (β= –0.31, p = 0.002, CI = –0.51, –0.12). Retrospective and general ordinal-rated SCD was associated with associative memory (β= –0.25, p = 0.012, CI = –0.44, –0.06; β= –0.29, p = 0.003, CI = –0.47, –0.10) and list learning only (β= –0.25, p = 0.014, CI = –0.45, –0.05; β= –0.28, p = 0.004, CI = –0.48, –0.09). Conclusion: Ordinal age-anchored SCD appears better suited than other SCD measurements to detect early cognitive dysfunction characteristic of preclinical AD.

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ObjectiveSubjective cognitive decline (SCD) has emerged as one of the first manifestations of Alzheimer’s disease (AD). However, discrepancies in its relationship with tests of memory and other cognitive abilities have hindered SCD’s diagnostic utility. Inter-individual heterogeneity in metamemory, or memory awareness, and the use of clinical measures of cognition lacking sensitivity to early cognitive dysfunction, may contribute to these discrepancies. We aimed to assess if the relationship between SCD and markers of early cognitive dysfunction is moderated by metamemory abilities.MethodsThe sample included 79 cognitively healthy older adults (77% female, 68% White, and 32% Black participants) with a mean age of 74.4 (SD = 6.1) and 15.9 (SD = 2.7) years of education. Metamemory was assessed using an episodic Feeling of Knowing test with four 5-item trials. Outcome measures included a resolution metric defined as a gamma correlation reflecting the accuracy of item-level predictions (“Will you know the correct answer?”). Early cognitive dysfunction was measured through the Loewenstein-Acevedo Scale for Semantic Interference and Learning (LASSI-L) and the Short-Term Memory Binding Test (STMB), measures sensitive to preclinical AD. SCD was assessed with a 20-item questionnaire that asked participants to compare themselves to others their age on a 7-point Likert scale. Regression analyses examined whether a potential relation between SCD and early cognitive dysfunction was moderated by metamemory.ResultsSubjective cognitive decline was associated with susceptibility to semantic proactive interference such that greater complaints were associated with increased susceptibility to semantic proactive interference (b = −0.30, p = 0.003) only. Metamemory moderated the association between SCD and susceptibility to and recovery of semantic proactive interference such that those with more accurate metamemory showed a stronger association between increased complaints and susceptibility to semantic proactive interference (b = −0.71, p = 0.005; b = −0.62, p = 0.034). Metamemory, however, did not moderate the association of SCD with retroactive semantic interference nor short term memory binding.DiscussionThe accuracy of an individual’s metamemory, specifically their ability to adjust moment to moment predictions in line with their performance, can influence the extent to which SCD maps onto objective cognition. Such self-referential assessment should be considered when interpreting SCD.

Background and objectives:This prospective study seeks to examine the utility of SCD as a marker of future progression to dementia in a community-based cohort of non-Latinx White, non-Latinx Black and Latinx individuals. Debate surrounds the utility of Subjective Cognitive Decline (SCD), the subjective perception of decline in one’s cognition before such impairment is evident in traditional neuropsychological assessments, as an early indicator of impending Alzheimer’s disease. Unfortunately, most studies examining SCD have been conducted in non-Latinx White samples and commonly exclude groups of individuals shown to be most vulnerable to dementia.Methods:Participants were enrolled into this cohort study from the Washington Heights–Inwood Columbia Aging Project (WHICAP) if they were cognitively unimpaired, had baseline measurement of SCD and self-identified as non-Latinx White, non-Latinx Black or Latinx. SCD was measured as a continuous sum of 10-items assessing cognitive complaints. Competing risk models tested main effects of baseline SCD on progression to dementia. Models were adjusted for age, sex/gender, years of education, medical comorbidity burden, enrollment cohort and baseline memory test performance with death jointly modelled as a function of race/ethnicity.Results:A total of 4,043 (1,063 non-Latinx White, 1,267 non-Latinx Black and 1,713 Latinx) participants were selected for this study with mean age of 75 years, 67% women and with a mean follow up of 5 years. Higher baseline SCD was associated with increased rates of incident dementia over time in the full sample (HR=1.085, CI=1.047, 1.125, p<.001) as well as within Latinx (HR=1.084, CI=1.039, 1.130, p<.001) and Black individuals (HR=1.099, CI=1.012, 1.194, p=.024).Discussion:Overall results of this study support SCD as a prodromal marker of dementia in a multiracial community sample, and in Latinx and non-Latinx Black individuals in particular. As models examining the risk of dementia were adjusted for baseline memory test performance, results support the idea that SCD, a subjective reflection of one’s own current cognitive functioning, contributes information above and beyond standard memory testing. Current findings highlight the importance of carefully evaluating any memory concerns raised by older adults during routine visits and underscore the potential utility of screening older adults for SCD.