Estimating annual rate of decline: prospective, longitudinal data on arm tremor severity in two groups of essential tremor cases
- 1GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- 2Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- 3Taub Institute for Research on Alzheimer's Disease and the Ageing Brain, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- 4Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA
- Correspondence to Dr E Louis, Unit 198, Neurological Institute, 710 West 168th Street, New York 10032, USA;
Contributors The statistical analyses were conducted by EDL.
- Received 10 September 2010
- Accepted 22 October 2010
- Published Online First 24 March 2011
Background Despite its high prevalence, there are surprisingly few prospective, longitudinal data on the clinical course of essential tremor (ET). Patients themselves often want to know from their treating physician whether and by how much their tremor is expected to worsen over time.
Methods As part of two research protocols, prospective, longitudinal data were collected on tremor severity in two samples of ET cases (44+39 cases, combined n=83). At a baseline and one follow-up evaluation, a detailed clinical assessment was performed and action tremor in the arms was rated by a senior movement disorders neurologist using a standardised clinical rating scale (Total Tremor Score (TTS), range 0–36).
Results In the first case sample, TTS increased annually by 0.32±0.89 points (ie, an annual increase of 5.3±17.1% (median 1.8%) from the mean baseline score). TTS increased by ≥0.5 points in 23/24 (95.8%) cases followed for ≥5 years. In the second sample, TTS score increased annually by 0.64±1.49 points (annual increase of 3.1±8.1% (median 2.0%) from the mean baseline score). TTS increased by ≥0.5 points in 11/15 (73.3%) cases followed for ≥5 years. No baseline factors were identified that predicted annual change in TTS.
Conclusions Most ET cases exhibited a progressive worsening in tremor scores with time such that the average annual increase in tremor severity from baseline was estimated to be between 3.1% and 5.3% and the median annual increase from baseline was between 1.8% and 2.0%. These published estimates will hopefully be a useful prognostic guide for clinicians and their patients.
Funding This research was supported by the National Institutes of Health Grant R01 NS39422.
Competing interests None.
Ethics approval This study was conducted with the approval of the Columbia University Medical Center.
Provenance and peer review Not commissioned; externally peer reviewed.