Dementia common in people with essential tremor

A prospective cohort study has shown that dementia is more common in individuals with essential tremor than in the general population, highlighting the need to identify those at risk early.

Essential tremor is a neurological condition that causes involuntary and rhythmic shaking of the head, legs, or voice. The trembling occurs most often in the hands, especially when doing simple tasks, such as drinking from a glass or tying shoelaces.

“While many people living with essential tremor experience mild tremor, in some individuals, the tremor can be quite severe,” said study author Dr Elan Louis from the University of Texas Southwestern Medical Center in Dallas, Texas, US at AAN 2024.

Louis and his team analysed data from 222 patients with essential tremor at baseline. At least 177 had follow-up evaluations at 18, 36, 54, and 72 months for a mean observation period of 5.1 years. The mean age of the patients was 79 years. [Louis E, et al, AAN 2024, abstract S35-003]

Over 5 years, the cumulative prevalence of dementia was 18.5 percent. The average annual conversion rate of mild cognitive impairment to dementia was 12.2 percent.

“The rates of dementia were thrice higher than the general population, although not as high as those reported for Parkinson’s disease,” Louis reported. “As for mild cognitive impairment, the cumulative prevalence was almost double that of the general population.”

While he explained that most people with essential tremor would not develop dementia, “the 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.”

Prevalence increases with advancing age

Essential tremor affects about 0.3–0.9 percent of the general population worldwide. [Sci Rep 2022;12:7669]

In Singapore, the prevalence rate of essential tremor was reported to be 2.37 per 1,000 in 2005. The rate was significantly higher in men (p=0.01) and increased dramatically with age (p<0.001). Looking at the race, Indians were 1.8 times more likely to have essential tremors than the Chinese. [Parkinsonism Relat Disord 2005;11:233-239]

In the US, essential tremor affects approximately 7 million people, representing more than 2 percent of its total population. The prevalence increases with age, affecting 0.8 percent of those between 18 and 30 years and slightly more than 8 percent of those aged 85 years and older. [Adv Ther 2022;39:5546–5567]

However, public recognition of the disease and its impact remains low. Importantly, increasing evidence suggests patient impact extends beyond tremor symptomatology.

“Despite recent attention given to cognitive impairment in essential tremor, only a few studies had examined conversion rates to diagnoses of mild cognitive impairment and dementia,” said Louis. “Hence, we conducted this study.”

After cognitive assessments, the patients were classified as having either normal cognition (n=168), mild cognitive impairment (n=35), or dementia (n=19) at baseline. During follow-up, 59 were diagnosed with mild cognitive impairment, and 41 had dementia.

The results were compared with data from historical controls and patients with Parkinson’s disease.

The cumulative prevalence of mild cognitive impairment was 26.6 percent, almost double that of the general population (14.5 percent).