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Comment by spike021 | Hacker News Reader

This is.... a bit depressing considering I have had essential tremor probably since I was about 12 or so years old.

Look, astronomically few people are at baseline or zero risk for all ailments. Essentially everyone is genetically or environmentally predisposed to an increased relative risk of some many terrible things that could befall them in the future.

Some people get to know about some of those biases ahead of time, some people don't get to know about them at all.

This is now on your list. When you're in your seventies, and assuming continued research in this area doesn't refine in a way that excludes your case, you may be more likely to have dementia than some random person you know without ET. Relatively few people get diagnosed with dementia though, and that includes relatively few people with ET (although, apparently, more), so who really knows.

Meanwhile, the rando that you picked to compare yourself to has their own known or unknown 3x risk for pancreatic cancer or aortic aneurism or kidney failure or something, and -- like you -- will probably not develop that particular condition anyway.

This should not be read as "oh shit, I'm going to develop dementia because of this damned ET!" so much as "oh, well, I now know I should be extra attentive to early dementia symptoms in as I get older since ET might occasionally be associated with it"

The dementia rate is 25% at 80 and raises to 37% at 90.

You know those numbers reflect survivor bias, right? By 80 and 90, most peers have already been lost to other organ failures, cancers, etc -- if longevity is important to them, most people would be lucky to be in those populations instead of the in much larger populations no longer being counted at all.

> By 80 and 90, most peers have already been lost to other organ failures, cancers, etc

In many wealthy countries, life expectancy at birth is greater than 80, which means that the average 80 year old, >50% of their same-age peers will still be alive. By age 90, what you say would be true.

In that case, you have early onset essential tremor, not age-related essential tremor. I believe only age-related essential tremor has increased risk of dementia. For example:

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).

https://movementdisorders.onlinelibrary.wiley.com/doi/10.100...

However, I think essential tremor needs more research in general.

We're really going to have to wait until the paper comes out to evaluate this. They compared to the general population, and there is a good chance that the participants in the study were severe enough to have approached a neurologist for care. That's not going to be representative if it's true. It will also matter whether the diagnostic process was rigorous. Basically...don't worry yet if you can help it.

>Essential tremor is associated with dementia: Prospective population-based study in New York (2009)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2731620/

ABSTRACT

Background: Mild cognitive deficits, mainly in frontal-executive function and memory, have been reported in patients with essential tremor (ET). Furthermore, an association between ET and dementia has been reported in a single population-based study in Spain. This has not been confirmed elsewhere.

Objective: To determine whether baseline ET is associated with prevalent and incident dementia in an ethnically diverse, community-based sample of elders.

Methods: Community-dwelling elders in northern Manhattan were enrolled in a prospective cohort study. Baseline ET diagnoses were assigned from handwriting samples. Dementia was diagnosed at baseline and follow-up using DSM-III-R criteria.

Results: In cross-sectional analyses, 31/124 (25.0%) ET cases had prevalent dementia vs 198/2,161 (9.2%) controls (odds ratio [OR]unadjusted = 3.31, 95% confidence interval [CI] = 2.15–5.09, p < 0.001; ORadjusted = 1.84, 95% CI = 1.13–2.98, p = 0.01). In prospective analyses, 17/93 (18.3%) ET cases vs 171/1,963 (8.7%) controls developed incident dementia (hazard ratio [HR]unadjusted = 2.78, 95% CI = 1.69–4.57, p < 0.001; HRadjusted = 1.64, 95% CI = 0.99–2.72, p = 0.055).

Conclusions: In a second population-based study of elders, essential tremor (ET) was associated with both increased odds of prevalent dementia and increased risk of incident dementia. Presence of dementia, therefore, appeared to be greater than that expected for age (i.e., a disease-associated feature). Rather than attributing cognitive complaints in patients with ET to old age, assessment and possible treatment of dementia should be routinely incorporated into the treatment plan.

Thanks. The best way to evaluate this is the prospective analysis, adjusted for control variables. The confidence interval on that hazard ratio includes 1.00, so the null hypothesis that there is no difference stands.

For the cross-sectional analysis, essential tremor was associated with dementia, but it gives no information as to whether ET increases risk for later dementia vs. dementia raises risk of ET.

Finally, the criteria used for dementia diagnosis are the psychiatric criteria from 4 DSM editions ago, though the criteria have been revised and updated numerous times by neurologists and other neuroscientists (i.e. those who work with essential tremor).

At least the sample was community-based instead of clinic-based.

FWIW my grandfather also had tremors and his final years had dementia. So at least for me this could be some genetic validation.

We just don't know when my grandfathers tremors began. We always figured it was more of a WWII/Holocaust survivorship PTSD symptom.

Understood. It's tough not to personalize findings like this. ET is heritable and dementia is heritable to some extent, but that doesn't mean one causes the other. I'm not saying you have nothing to worry about, but this paper shouldn't make you more worried than anyone with a grandparent with dementia. My best to you.

For sure, thanks for the reassurance.

Same :( Also family history of dementia and Parkinson’s but I tested clear for Parkinson’s markers

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