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Dementia was more common in people with essential tremor than in the general population, a prospective cohort study found.

Over 5 years, the cumulative prevalence of dementia was 18.5% and the average annual conversion rate of mild cognitive impairment to dementia was 12.2%, reported Elan Louis, MD, of the University of Texas Southwestern Medical Center in Dallas, and co-authors in an abstract released in advance of the American Academy of Neurology annual meeting.

These rates were three times higher than those in the general population and approximately one-half the magnitude of those reported in Parkinson's disease, the researchers stated.

"While the majority of people with essential tremor will not develop dementia, our findings provide the basis for physicians to educate people with essential tremor and their families about the heightened risk, and any potential life changes likely to accompany this diagnosis," Louis said in a news release.

Essential tremor is a common movement disorder. Its defining feature is a kinetic tremor of the arms, but other parts of the body, like the head or lower limbs, also may be involved.

The tremor can affect daily activities like eating. "While many people living with essential tremor experience mild tremor, in some individuals, the tremor can be quite severe," Louis said.

Recent that about 6.4 million adults in the U.S. have essential tremor. Its prevalence is strongly correlated with age, ranging from 0.8% in people 18-30 years old to 8.2% among those 85 and older.

Prior research has shown that in patients with essential tremor, but evidence that people with are at a greater risk of developing dementia has been inconclusive.

Dementia in essential tremor is associated with loss of functional ability and a doubling of mortality rate, Louis and co-authors pointed out. "Despite recent attention to cognitive impairment in essential tremor, few studies examine rates of conversion to diagnoses of mild cognitive impairment and dementia," they noted.

The researchers evaluated 222 patients with essential tremor at baseline; mean age was about 79 years. A total of 177 essential tremor patients participated in follow-up evaluations at 18, 36, 54, and 72 months. The mean observation period was 5.1 years.

Participants had detailed cognitive assessments and were assigned a diagnosis of either normal cognition, mild cognitive impairment, or dementia at baseline and during follow-up. These results were compared with data from historical controls and Parkinson's patients.

At baseline, 168 people had normal cognitive skills, 35 had mild cognitive impairment, and 19 had dementia. During follow-up, 59 people were diagnosed with mild cognitive impairment and 41 were diagnosed with dementia.

The cumulative prevalence of mild cognitive impairment was 26.6% -- almost double that of the general population (estimated at 14.5%), but less than that in Parkinson's disease (estimated at 40%).

"We present the most complete exposition of the longitudinal trajectory of cognitive impairment in an essential tremor cohort," Louis and colleagues wrote. "Our data indicate that the prevalence of and conversion rates to dementia in essential tremor fall between those associated with the natural course of aging and the more pronounced rates observed in individuals with Parkinson's disease."

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