Risk of incident dementia in essential tremor: A population‐based study

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Abstract
Essential tremor (ET) is a late-life neurological disease. Mild cognitive deficits as well as an association with prevalent dementia have been reported in recent case–control studies. We determined whether ET was associated with an increased risk of incident dementia. In a population-based study of older people in central Spain (NEDICES), nondemented ET cases and controls were followed prospectively. Incident dementia at follow-up was diagnosed using DSM-IV criteria and the risk of incident dementia was estimated in ET cases versus controls using Cox proportional hazards models. 3,891 participants had a mean duration of follow-up of 3.2 years. Sixteen (7.8%) of 206 ET cases developed incident dementia versus 145 (3.9%) of 3,685 controls (unadjusted relative risk [RR] = 2.08, 95% CI = 1.24–3.50, P = 0.006 and adjusted RR = 1.66, 95% CI = 0.99–2.80, P = 0.054). In an adjusted model, ET cases with tremor onset after age 65 years were twice as likely to develop incident dementia than were controls (RR = 1.98, 95% CI = 1.14–3.45, P = 0.01), whereas ET cases with tremor onset < age 65 years and controls were equally to develop incident dementia (RR = 0.74, 95% CI = 0.19–3.20, P = 0.79). Although ET is often considered a benign condition, in this prospective, population-based study, elderly-onset ET was associated with an increased risk of incident dementia. The basis for this dementia, which is not known, requires additional study. © 2007 Movement Disorder Society