Objective: To investigate whether tremor features are associated with cognition in cognitively normal subjects with essential tremor (ET).

Background: There is increasing recognition that ET is a heterogeneous disorder that includes motor and non-motor features such as cognitive heterogeneity. Individuals with ET are at increased risk of dementia and have been shown to have variable cognitive profiles [1-4]. The extent to which this cognitive variability associates to motor phenotypes remains unclear. The goal of this study was to determine whether tremor features are associated with cognition in cognitively normal adults with ET.

Method: Participants were enrolled in COGNET, a prospective, longitudinal study to characterize a cohort of ET subjects using motor and neuropsychological measures. Subjects were excluded from analysis if 1) they were missing cognitive data (n=41); 2) had a diagnosis of dementia or mild cognitive impairment (n=42); or 3) had Parkinson’s disease or another non-ET cause of tremor (n=10), for a final sample size of 149. Diagnosis of ET was confirmed from a videotaped neurological exam. Participants completed cognitive tests assessing the domains of memory, executive function, attention, visuospatial ability, and language. Sample z scores were computed for each domain and an average z score was calculated to reflect global cognition. Linear regression models were used to examine the association between tremor features and cognitive domains, adjusting for age, education, sex, and number of medications.

Results: Mean age and range of subjects was 76.7 (55-95) years. Mean disease duration and range was 38.2 (2-86) years. In adjusted linear regression models, tandem gait missteps were associated with worse global cognition (b = -0.21, p=0.006), memory (b= -0.25, p =0.01), and executive function (b = -0.17, p=0.01), and tremor severity was associated with worse visuospatial ability (b = -0.12, p = 0.03). Cranial tremor, intention tremor, and presence of dystonia were not associated with any cognitive domains (p>.05).

Conclusion: Preliminary analyses show that several motor features of ET are associated with cognition cross-sectionally above and beyond demographic effects. This suggests that tremor features could be used as a marker of cognitive heterogeneity. Future studies should evaluate whether tremor features are associated with cognitive change over time.

References: 1. Louis, E.D., et al., Faster rate of cognitive decline in essential tremor cases than controls: a prospective study. Eur J Neurol, 2010. 17(10): p. 1291-7. 2. Louis, E.D., et al., Poorer Cognitive Performance in Patients with Essential Tremor-Parkinson’s Disease vs. Patients with Parkinson’s Disease. Front Neurol, 2015. 6: p. 106. 3. Sinoff, G. and S. Badarny, Mild cognitive impairment, dementia, and affective disorders in essential tremor: a prospective study. Tremor Other Hyperkinet Mov (N Y), 2014. 4: p. 227. 4. Cersonsky, T.E.K., et al., Profiles of Normal Cognition in Essential Tremor. J Int Neuropsychol Soc, 2020. 26(2): p. 197-209.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/tremor-features-associated-with-cognition-in-cognitively-normal-subjects-with-essential-tremor/