Mapping cognitive trajectories in older adults with essential tremor

Abstract

AbstractBackgroundOlder adults with essential tremor (ET) are at increased risk for Alzheimer’s disease (AD) and related disorders. Examining cognitive trajectories within this population will enable better identification of individuals who evidence accelerated rates of change. Here we examine how variability in baseline cognitive performance affects trajectories of cognitive change within three subgroups of cognitively normal older adults: 1) those whose baseline neuropsychological scores were entirely within normal limits (WNL); 2) those with at least one low score considered to have unlikely clinical significance (UCS); and 3) those with at least one low score considered to have possible clinical significance (PCS).MethodOlder adults with ET completed comprehensive neuropsychological testing and clinical interviews, and 159 received a consensus diagnosis of cognitively normal. Participants were then subdivided into one of three categories defined above: WNL (N = 66, 75.38 ± 8.96 years of age), UCS (N = 54, 76.35 ± 10.25 years), and PCS (N = 37, 80.22 ± 9.00 years). Generalized estimating equations (GEE) were used to compare rates of change in global cognition, memory, executive function, attention, visuospatial, and language z‐scores over time across these groups. Participants were seen for two to four visits (24.98 ± 20.29 months). Models were adjusted for age, gender, and years of education.ResultAll three groups, WNL (β = ‐.005, p = .028), UCS (β = ‐.006, p = .011), and PCS (β = ‐.012, p = .002), evidenced decline in their memory performance over time, with the latter groups declining faster than the WNL group. Relative to the WNL and UCS groups, the PCS group also declined faster over time in overall cognition (β = ‐.010, p = .029) and in language (β = ‐.024, p = .035).ConclusionHeterogeneity in cognitive performance among cognitively normal older adults with ET predicts trajectories of cognitive decline longitudinally. Specifically, rates of decline were slowest in those with entirely normal test scores, and greatest in those whose scores were considered to have possible clinical significance. These preliminary results provide a starting point for further inquiry into the role of nuanced cognitive profiles in predicting rates of decline, impairment, and dementia in ET cases who may initially be labeled as “cognitively normal.”