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Tremor that develops in old age linked to dementia
Last Updated: 2006-06-02 16:32:16 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Essential tremor (ET) that starts after 65 years of age is associated with an increased risk of dementia, particularly Alzheimer's disease, according to a large study conducted in Spain. However, when ET onset is earlier, there appears to be no increased risk.
Essential tremor refers to a movement disorder that can't be attributed to any other condition, as opposed to the tremor that accompanies Parkinson's disease. ET is one of the most common movement disorders and although it may be disturbing, it is usually not debilitating.
The researchers evaluated 3,655 subjects between 1994 and 1995, and again in 1997 to 1998. The assessment included a questionnaire and a battery of neuropsychological tests. Two tests were administered to diagnose dementia, and subjects with ET or dementia underwent a neurologic examination. The findings are reported in the journal Neurology.
Dr. Julian Benito-Leon, from Mostoles General Hospital in Madrid, and his associates report that 235 (6.4 percent) of the participants were demented, and 273 (7.5 percent) had ET.
Taken as a whole, 11.4 percent of ET cases had dementia, compared to 6.0 percent of those without ET.
After factoring in demographic information, education, alcohol consumption, smoking, and other patient variables, only the 182 subjects whose ET started after age 65 were significantly at risk for dementia. There was no significant association between younger onset of ET and dementia.
Most of the cases with dementia -- 74.9 percent -- had Alzheimer's disease. Again, older onset of ET was associated with a higher rate of Alzheimer's disease, but none of the younger onset ET cases had Alzheimer's disease.
Benito-Leon's group also notes that none of the ET cases had features of parkinsonism. The many questions that arose from this study have led the investigators to initiate another study to further examine the relationship between ET and dementia.
SOURCE: Neurology, May 23, 2006.
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