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

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.