Incidence of essential tremor in three elderly populations of central Spain

OBJECTIVE: To estimate the incidence of essential tremor (ET) in three populations in central Spain using data from the Neurologic Disorders in Central Spain (NEDICES), a population-based survey of elderly subjects (65 years and older). METHODS: Individuals were evaluated at baseline (1994 to 1995) and at follow-up (a median of 3.3 years later in 1997 to 1998). The evaluation included a screening question for ET and a neurologic examination, when possible. RESULTS: Of 5,278 subjects evaluated at baseline, there were 256 prevalent ET cases. Eighty-three incident ET cases were identified among 3,942 individuals assessed at follow-up. The adjusted annual incidence rate (per 100,000 person-years) in the population aged 65 years and older was 616 (95% CI: 447 to 784). Sixty-four (77.1%) of 83 incident cases had not been diagnosed before our assessment. CONCLUSIONS: The incidence of ET may be higher than previously recognized because a large proportion of patients with ET may never seek medical attention.