Too much coffee can cause brain to shrink, raise risk of dementia by 53 percent | Hacker News Reader

Too much coffee can cause brain to shrink, raise risk of dementia by 53 percent

studyfinds.org

I'm going to completely disregard this study. "What would the world look like if this study were true?"

53% is such a large effect size that if the study were anywhere near accurate, I'd expect to have seen many other similar studies, and other knock-on effects (nothing in the body is isolated, even dementia). But we all know that studies routinely find no or only positive health benefits associated with drinking coffee.

I bet this study is junk.

The statistic is relative: "a 53% increase" is relative to some baseline. It does not mean the absolute risk is raised to 53%.

Without context these relative form are meaningless, and they are presented this way annoyingly commonly by media. For example if the baseline absolute risk is 0.0100% then the study suggests the increase would raise that to 0.0153% in absolute terms... and no I do not know what the baseline is, the headline is truly meaningless to me.

Figure 2 of the study says the ">6 cups/day" cohort had 123 of 9,265 dementia cases (1.3%).

The "1-2 cups/day" reference group had 953 of 123,516 dementia cases (0.77%).

hah, so my exaggerated example was only 1 order of magnitude off.

I agree, this contradicts several studies that concluded the opposite. Here's a couple I found after a quick search:

There were no significant associations between coffee or caffeine intake and risk of cognitive impairment, overall dementia, AD, VaD, or moderate/high levels of the individual neuropathologic lesion types.

https://content.iospress.com/articles/journal-of-alzheimers-...

Coffee drinkers at midlife had lower risk of dementia and AD later in life compared with those drinking no or only little coffee adjusted for demographic, lifestyle and vascular factors, apolipoprotein E ε4 allele and depressive symptoms.

https://content.iospress.com/articles/journal-of-alzheimers-...

It seems this is not the first study. The introduction says

>A Mendelian randomisation study has provided evidence for a potential adverse effect of higher coffee consumption on the risk of Alzheimer’s disease, with each cup of coffee increasing the risk by 26% (13). However, observational evidence is inconsistent, and of the 11 most recent longitudinal cohort studies on habitual coffee intake and dementia risk, five supported a possible protective effect (14–18), whereas six studies found no association (19–24).

... and it looks like we have a long way to go before there's a conclusion.

On the other hand, caffeine is a vaso-constrictor which reduces blood supply to the brain. This is very old news and replicated many times from even 1935. What are the effects of this? To go full forward we have https://www.biorxiv.org/content/10.1101/2021.07.01.450708v1.... (July 2 2021) "Our findings unveil that conventional daily caffeine intake does not provide sufficient time to clear up psychoactive compounds and restore cerebral responses, even after 36 hours of abstinence. They also suggest investigating consequences of a paraxanthine accumulation during daily caffeine intake."

As an avid coffee drinker I'd like to feel able to agree with your conclusion but I'll limit the amount wagered.

https://pubmed.ncbi.nlm.nih.gov/19219847/

Coffee has a lot of other components such as polyphenols which generally have a beneficial effect. May be that this counteracts the possible negative consequences of caffeine under certain conditions.

Every time I see studies like this it reminds me of the Roche Biochemical Pathways

http://biochemical-pathways.com/#/map/1

For starters, there are over 1000 chemical compounds in coffee.

For a 53% effect, let's toss out "coffee" and go with a specific compound. Are we talking about pH effects? The possible carcinogens with roasting? Caffeine? Does Diet Coke have this effect? The fertilizer used during growing? Does coffee candy with natural flavor have this effect?

After that, how do the biochemical pathways and inherent homeostasis handle this change?

Forget it. The rabbit hole is endless with studies like this.

When people wonder how others can get stuck in their own echo chamber, remember this post. They didn't read the article, misinterpreted the stats, and just ignored the results since it didn't conform to their preconceptions.

I don't really disagree with you, but 53% is not that enormous of an effect. To put this in perspective, tobacco smoking raises the risk of lung cancer by about 3000%.

It should be noted that "too much" is 6 cups per day, which I suspect very few people drink consistently.

Really?

A common measurement standard for a cup of coffee is 6 oz.

If this is a 6 oz cup of normal-strength (i.e., weak) coffee, then that's only 36 oz, or three soda cans. What if you consume what's now considered normal, which seems quite strong? Two soda cans?

How large is a mug, which people associate conceptually with "a cup"?

I think it would be the amount of caffeine per cup. My guess is that a standard coffee cup would be 80-100mg. 600mg is a hell of a lot of caffeine - on rare days when I have 400 I feel very well used at the end of the day.

Damn. Now I'm worried. Consuming less than 6 coffees a day is more unusual for me.

I think you missed the "6+ coffees a day" part.

Title:

>Too much coffee can cause your brain to shrink

>cause

Conclusion from study:

>High coffee consumption was associated with smaller total brain volumes and increased odds of dementia.

>associated

I drink objectively too much coffee so "associated" is the best word I've heard all day.

what's "too much?" more than 4 liters a day? 8?

Really depends who you ask. For what it's worth I use the large meta study on cardiovascular health to establish guidelines, and it seems like 3-5 cups a day is not just fine but "optimal" under this study. [1]

[1] https://www.ahajournals.org/doi/full/10.1161/circulationaha....

"Consumption of >6 cups/day was associated with 53% higher odds of dementia compared to consumption of 1–2 cups/day"

Sleep hygiene is important, and it's critically important not to drink coffee late in... well, in the second half of the day really.

A lack of sleep is also a serious risk factor for dementia.

How much of this is just chronic sleep deprivation, I wonder?

There is also the possibility that the causation happens in reverse: those with early symptoms of dementia could be self-medicating with excess caffeine.

Or the coffee could be preventing other health problems so that more drinkers make it to dementia.

I doubt the study would fail to control for this; it's literally the most basic thing you can control for.

I drink coffee after dinner and sleep like a baby (an expression invented by those who have not had babies, but you know what I mean). But it was not always thus. The secret is drug tolerance!

That's about 1000mg of caffeine a day. A gram a day is diminishing returns for the average coffee drinker, and may signal addiction. Addiction is dangerous in itself, so we might explain the outrageous results of this study in that way. A lifetime on the edge is a recipe for disaster!

Depending on how and what you brew, a cup of coffee can contain 35, 100 or 150 mg of caffeine. People also invariably consider a mug of coffee the same as a cup of coffee.

A common reference in $my_country is that a cup (15 cl) of coffee usually contains circa 70 mg of caffeine.

It's really sketchy how their conclusions don't show the rate for 0 cups/day or 2-6 cups per day.

Figure 2 in the study says

  Adjusted for all covariates
  Odds
  1.09  None
  1.19  Decaf
  1.02  <1 cup/day
  1.00  1-2 cups/day
  1.02  3-4 cups/day
  1.13  5-6 cups/day
  1.53  >6 cups/day

Earlier they say

> We used light coffee drinkers (1–2 cups/day), instead of nondrinkers, as the reference group to avoid bias from individuals with poor health, who may avoid coffee due to their health status (49, 50).

Ahh, I could only see the truncated version on the site.

Though that's the reason they claim to have picked that group, as they were using biobank data they likely already knew the rates before the study started. Picking the lowest cohort from the get go is almost more sketchy.

Given the decaf numbers, it looks like caffeine is having a protective effect on the negative effects from the rest of the coffee!

Study in 6 months: “More than 6 cups of coffee not associated with dementia or brain size changes.”

It will be funded by the National Coffee Association.

Why on earth do we measure coffee in cups? People drink more espresso and other drinks like cold brew than ever these days, just talk about caffeine in mg

Cups is actually more specific, if we're relying on the baseline of regular drip-brew joe. There's other factors at play than just caffeine intake or else we'd have heard about this surrounding energy drinks and meal replacement supplements.

Granted, I haven't read the study, but the coffee/caffeine invariant just came to mind when I read your comment.

There are certainly other factors, but a cup is far from the specific solution you seek [0]. There's only one country that has current unit definition of a cup (the US), which is 8 (US) fluid ounces (fl.oz) (or 236.6ml), or differently as a "legal" cup at 240ml [1]. It used to be defined as 10 Imperial fl.oz in the UK (284ml), although rarely used. While much of the world defines a metric cup as 250ml. But then there's the exception that is coffee.. a cup of coffee in the US is the product of using 5 fl.oz producing approximately 4 fl.oz of coffee[0]

A "cup": 118-284ml

[0]: https://en.wikipedia.org/wiki/Cup_%28unit%29 [1]: https://www.fda.gov/regulatory-information/search-fda-guidan...

Ah, you've out-semantic'd me, I was referring to cups as being a more specific term of the different modes of coffee consumption. I'm in favor of the metric system. I did not know that the definition of a "cup" of coffee in the US was under such a broad variance.

Thanks for the info!

Yes. Using caffeine in mg would make for more sense to use.

RE: https://www.fda.gov/consumers/consumer-updates/spilling-bean...

There's too little information on the sampling

> We conducted prospective analyses of habitual coffee consumption on 398,646 UK Biobank participants (age 37–73 years), including 17,702 participants with MRI information. We examined the associations with brain volume using covariate adjusted linear regression, and with odds of dementia (4,333 incident cases) and stroke (6,181 incident cases) using logistic regression.

The study had access to a relatively large dataset, but how many people have dementia and drink >6/day?

Also, for understanding the effects of coffee drinking on dementia the data set has to be tracked for a decent amount of time... decades? I have very strong doubts about the integrity of the data.

How long do you have to drink >6/day before that kicks in? obviously doing it once isn't going to cut it.

Am I reading this correctly that they're claiming 1.5% of the participants had strokes due to coffee?

One thing I have noticed is that studies that end up with conclusions that sound like BS end up being BS studies.

The effect size of a 50% increase of dementia risk sounds way to high for coffee. Seems like there is a good chance of some correlated variable they are missing or a faulty assumption.

If I read the abstract correctly they found an inverse correlation between coffee consumption and brain volume, but since it was not a longitudinal study it doesn't prove that coffee is correlated to brain shrinkage?

I'm pretty sure there's a study I read that said coffee reduces the risk of dementia.

Here's my rule for most everything in life: everything in moderation. When I skip a day with coffee, I enjoy it a lot more the next day.

this is confusing. is it a metric cup of coffee or a 'cup of coffee' which is apparently 6 oz....

why use cups of coffee...do they mean the measurement or the receptacle.

how does one now measure their consumption? what is a Starbucks in cups?

I wanted to answer your question with a smug link to the study, but they use the same useless units:

https://www.tandfonline.com/doi/abs/10.1080/1028415X.2021.19...

I'm going to assume "cup" means "vessel that contains hot liquid" and rate 1 cup as around 250mL of brewed coffee, with a range of 150mL to 600mL. Not sure what that means for the results, but yeah, not a good unit.

And in fact:

> Habitual coffee intake was self-reported as cups per day, as part of the touchscreen questionnaire at baseline with the question ‘How many cups of coffee do you drink a day?’ (38).

So, yes, it's self-reported in a non-standardized unit.

I didn't read the article, but I have yet to encounter anyone measuring coffee by the imperial cup. Also never heard of a "metric cup of coffee".

Nothing about coffee is precise in most cases.

Head: Too many web pages to fill may be associated with garbage research getting published.

Subhead: Journalist says "Not my fault! My editor told me 'fear sells' "

https://www.tandfonline.com/doi/abs/10.1080/1028415X.2021.19...

Brain volume is overrated.

See

[1] https://iflscience.com/brain/man-tiny-brain-lived-normal-lif...

First Google result says a cup is 250 ml, is this right? I usually drink one and a half mug per day, which is about 750 ml. I I did stop drinking coffee after 18 o clock and I'm sleeping way better.

Coffee cups as measured on the brewing machine is only about half that size.

OTOH, the researcher says 1-2 cups is the normal amount in the article. To me that implies a larger cup size.

little bit less than 250mL, but pretty close, yea

Any study that concludes with ~50% is random noise.

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