Correlates of functional disability in essential tremor.
The decision to treat patients with essential tremor (ET) is based primarily on the functional impact of the tremor. Correlates of functional disability, apart from the severity of the tremor itself, have not been studied. The objective of this work was to study correlates of functional disability in ET, and to present data on the extent of functional disability in community-dwelling ET cases. ET cases and age-matched control subjects were ascertained from a tertiary referral center at Columbia-Presbyterian Medical Center and a community in northern Manhattan, N.Y. Subjects underwent a 2.5-hour evaluation, including a tremor disability questionnaire, a videotaped tremor examination rated by a neurologist, a performance-based test of function, quantitative computerized tremor analysis, the Hamilton Anxiety Rating Scale, and the depression module of the Structured Clinical Interview for DSM-IV. Seventy-six (85.4%) of 89 cases reported disability on > or =1 item on the disability questionnaire. In multivariate linear regression analyses, current major depression, Hamilton Anxiety Rating Scale score, age, and tremor severity were independently correlated with performance-based test scores. Twenty-seven (73.0%) of 37 community cases reported disability on > or =1 (mean = 8.4) item on the questionnaire, and 25 (67.6%) demonstrated moderate or greater difficulty on > or =1 (mean = 4.2) task in a performance-based test. Depression, anxiety, and age, independent of the severity of tremor, were associated with greater functional disability in ET, so that these factors must be considered when assessing the impact of new treatments in ET. Among a group of community-dwelling cases, approximately three-quarters reported disability, suggesting that the number of individuals who might receive some benefit from advances in the treatment of ET is probably a great deal larger than previously thought.