Directory, Epidemiology Biogen Cambridge, United States
Background: Essential tremor (ET) is an incurable neurological movement disorder with bimodal incidence that affects quality of life but not survival. It is often misdiagnosed, relying on exclusion of diseases with similar symptoms. Thus, estimating prevalence using administrative data is challenging.
Objectives: To estimate prevalence of ET using population-based community screening studies in defined geographical areas that ascertain disease using in-person interview and confirmation by qualified neurological examination.
Methods: We conducted a comprehensive literature review in PubMed and EMBASE of English language studies with age-stratified estimates published from January 2000 to March 2022. From 652 identified studies, 16 were included in our analysis. Age categories varied from study to study. We set the most frequently reported as target categories (18-30, 31-40, 41-49, 50-59, 60-64, 65-74, 75-84, 85+ years) and calculated prevalence estimates within these. The estimates from each study were extracted and assigned to the midpoint of the reported age category. Poisson regression with log-transformation was used to model age-category specific prevalence estimates (dependent variable) and the midpoint age of the reported age category (independent variable). The fitted model was used to calculate the prevalence at the midpoint age of the target age categories, which was assigned as the prevalence for the target age category. The final summary estimate for each target age category was calculated as the median of all prevalence estimates available for that age category.
Results: Significant heterogeneity was noted from study to study (I^2 >95%). Data suggested that prevalence is lower in Asian countries, thus two sets of prevalence estimates were calculated. Prevalence estimates in countries outside of Asia by target age categories were 0.004, 0.009, 0.017, 0.028, 0.035, 0.042, 0.078, and 0.106, respectively, while those in Asian countries were 0.000, 0.002, 0.003, 0.004, 0.007, 0.019, 0.026, and 0.042. Of the three studies with prevalence estimates across the adult age span, all showed a monotonic increasing relationship between prevalence and age.
Conclusions: Prevalence may be lower in Asian countries compared to other parts of the world, but more research is necessary to confirm this. While significant heterogeneity is noted from study to study, the data are derived from a variety of populations and offer a set of possible global estimates that continue to place ET among the most common movement disorders.
