Prevalence of essential tremor in three elderly populations of central Spain.

Although essential tremor (ET) is considered the most prevalent adult movement disorder, the available information on its prevalence and distribution worldwide is not completely understood. We investigated the prevalence and distribution of ET in three elderly Spanish populations using a door-to-door, two-phase approach. A brief screening instrument was administered on May 1, 1994 to subjects over 64 years old taken from the census of one urban municipality of Greater Madrid (quarter of Margaritas, Getafe), one urban district of Madrid (Lista), and one rural site (Arévalo county, Avila) (N = 5278). Study subjects were limited to those who screened positively (N = 472). To increase reliability, each patient was examined by 3 experienced neurologists, and was classified as having ET only when all 3 neurologists agreed (183 of 472). The present study was part of a large-scale epidemiological survey of neurological diseases, and served as a baseline investigation in a 3-year incidence study. Accordingly, 41 ET patients were identified when evaluating subjects who had screened positively for dementia, stroke, or parkinsonism, despite the fact that they had screened negatively for tremor; furthermore, 32 additional ET prevalent cases were detected when evaluating subjects who had screened positively for tremor in the second cross-sectional study (May 1, 1997), although they had screened negatively for tremor in the first cross-sectional study. We identified 256 persons (152 women, 104 men) with ET; of these, 87 patients (34.0%) reported having an affected relative. Two hundred and four (79.7%) of the subjects with ET were detected through this screening and had not been diagnosed previously. The prevalence of ET was 4.8% (95% CI = 4.2-5.4) for the total population; 4.6% (95% CI = 3.7-5.4) in men and 5.0% (95% CI = 4.2-5.8) in women. Age-specific prevalence increased with advancing age for both men and women. Despite the variability in worldwide data, ET is a frequently encountered disorder in elderly people. Furthermore, as ET may be seen as a relatively benign condition, a large proportion of patients may never seek neurological attention.