Incidence of essential tremor in three elderly populations of central Spain

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).

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.

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.

The incidence of ET may be higher than previously recognized because a large proportion of patients with ET may never seek medical attention.