Tremor in ostensibly normal elderly people.

Tremor in ostensibly normal people, aged 70-91, was assessed clinically and electrophysiologically with the goal of estimating the prevalence of abnormal tremor. Fifty men and 50 women, mean age 76.0 +/- 4.7 yrs, were recruited through advertisements for healthy volunteers (n = 50 "biased" control subjects) and from the spouses of patients referred to us for dementia or Parkinson's disease (n = 50 "unbiased" control subjects). All participants were interviewed and examined by the author. Tremor was assessed quantitatively with rating scales, triaxial accelerometry, electromyography, a digitizing tablet, and spectral analysis. Twenty-three people (23%) were judged clinically to have mildly abnormal tremor resembling mild essential tremor. Twelve people with abnormal tremor belonged to the biased group and 11 were in the unbiased group. The clinical diagnosis of abnormal hand tremor correlated well with the presence of motor unit entrainment in the forearm EMG and with writing or drawing tremor that was measurable with a digitizing tablet. Only 10 of 23 people with abnormal tremor were aware of their tremor, and none had been diagnosed previously by a physician. Nine of 77 people (11.7%) with normal tremor had a parent or sibling with possible essential tremor, and five of the 23 people (21.7%) with abnormal tremor had this family history. Mild undiagnosed tremor, resembling essential tremor, is common in this age group.