Population-based case-control study of cognitive function in essential tremor.

OBJECTIVES: To determine whether patients with essential tremor (ET) have cognitive deficits when compared with controls and whether the types of cognitive deficits reported previously are also found in this large sampling of patients with ET.

METHODS: A total of 232 patients with ET and 696 matched controls age 65 years or older (median 75 years) living in central Spain (the Neurologic Diseases in Central Spain study) underwent a neuropsychological assessment, including tests of global cognitive performance, frontal executive function, verbal fluency, and memory. Subjects also were asked whether they had forgetfulness.

RESULTS: Fifty-six patients with ET were previously undiagnosed; only 14 (6%) were taking medication for tremor. Adjusted for age, gender, education, premorbid intelligence, medications, and depressive symptoms, cases performed less well on most neuropsychological tests and especially tests of global cognitive performance (37-item Mini-Mental State Examination = 27.0 +/- 6.7 in cases vs 28.9 +/- 5.9 in controls, p < 0.001) and frontal executive function (Trail Making Test number of errors = 8.7 +/- 11.0 in cases vs 3.8 +/- 7.6 in controls, p < 0.001). Forgetfulness was reported in 117 (50.4%) patients with ET vs 300 (43.1%) controls (p = 0.05).

CONCLUSIONS: In a population-based sample of largely untreated patients with essential tremor, cases performed more poorly on formal neuropsychological testing than did their counterparts without tremor. A complaint of forgetfulness was also marginally more common in patients with essential tremor.