<h2>tl;dr: Not sure yet, but it looks promising</h2>
<hr>
<p>So there are a <a href="https://scholar.google.co.uk/scholar?hl=en&amp;q=coffee+alzheimers&amp;btnG=&amp;as_sdt=1%2C5&amp;as_sdtp=" rel="nofollow noreferrer">whole bunch</a> of studies that have been done that have investigated a potential link between coffee consumption and Alzheimers.</p>
<p>The problem, as always, is that these types of '<a href="https://en.wikipedia.org/wiki/Cohort_study" rel="nofollow noreferrer">cohort studies</a>' are really difficult. Basically the way it works is:</p>
<ul>
<li>Get a load of volunteers</li>
<li>By doing questionnaires, work out everything about them</li>
<li>Track them over a long period of time</li>
<li>See if there's a statistically significant link between combinations of behaviours (such as drinking coffee) and a particular outcome (diagnosis of Alzheimers)</li>
</ul>
<p>All the standard stuff applies here: you are not testing for <em>causation</em>, only for <em>correlation</em>. For example, ~80% of Americans drink coffee, but in other cultures this number varies a lot. If the coffee drinkers in your study are predominantly American, and the non-coffee drinkers are predominantly not, you have a whole bunch of confounding factors. Designing your study to avoid this kind of situation is really hard, especially when you're relying on volunteers.</p>
<p>There's also the issue of what exactly are you measuring? Someone might drink 3 cups a day now, but only has done for the past few years. Another person might drink 2 cups a day, but has done their whole life. Another person might drink 2 cups of decaff a day. Questionnaires are usually not sophisticated enough to capture this level of detail (partly because in your big expensive study you want to capture as much information about different behaviours as possible - not just coffee consumption).</p>
<p>Remember also that medical studies are <em>chronically</em> badly reported in the mainstream press. Even in 'high-brow' publications, by the time the headline-writers get their hands on a study, the message can have changed <em>wildly</em>. It's always worth trying to dig up the actual paper whenever new research is mentioned in the news. If no paper is linked, just ignore the headline.</p>
<p>One tool against all of this uncertainty is <a href="https://en.wikipedia.org/wiki/Meta_analysis" rel="nofollow noreferrer">meta-analysis</a>. This is where you look at every single study, weighted by how confident you are in the data (e.g. by weighting more to studies with more participants, and better questionnaires etc.). You then do some careful statistics work to get a measure of confidence across all of the studies. Think of it as a sophisticated way of 'averaging them out'.</p>
<p><a href="http://www.maneyonline.com/doi/abs/10.1179/174313206X152546" rel="nofollow noreferrer">One of these was done</a> in 2002. Only 4 studies had been done by then, but the conclusion was:</p>
<blockquote>
<p>Although our pooled estimates show that coffee consumption is inversely associated with the risk of AD, the four studies had heterogeneous methodologies and results. Further prospective studies evaluating the association between coffee consumption and AD are strongly needed.</p>
</blockquote>
<p>(Heterogeneous is science for 'different')</p>
<p>i.e., &quot;Not sure yet, not enough data, but it looks promising, give us more money for research.&quot;</p>

CC BY-SA 3.0
2015-02-09T13:46:44.863Z
2015-02-09T13:46:44.863Z
2020-06-18T08:36:22.093Z
fredley
<p>Many medical websites suggest so. If yes, then how? Alzheimer's is primarily incurable but then it can be delayed, how can coffee play a role?</p>

<p>References:</p>

<ul>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed/20182054">Pubmed - Caffeine as a protective factor in dementia and Alzheimer's disease</a>  </li>
<li><a href="http://www.medicaldaily.com/drinking-coffee-can-lower-alzheimers-risk-20-all-it-takes-3-cups-day-312410">Medical Daily - Drinking Coffee Can Lower Alzheimer's Risk By 20%, All It Takes Is 3 Cups A Day</a>  </li>
<li><a href="http://www.alzheimers.org.uk/site/scripts/news_article.php?newsID=1223">Alzheimers.org - Drinking coffee reduces your risk of dementia, says study</a></li>
</ul>

CC BY-SA 3.0
2015-02-09T12:40:51.427Z
Can you link to somewhere that makes the claim?
fredley
CC BY-SA 3.0
2015-02-09T13:27:33.360Z
Google Search Link: http://goo.gl/78hWjL
qedk
CC BY-SA 3.0
2015-02-09T13:30:56.797Z
Sorry, I didn't mean in general, I meant the specific ones you had found. On Skeptics, where they get a lot of questions like this, all questions must be backed up with sources. Although we probably wouldn't need a strict policy here, it's still good to prompt for such information on questions like this to make sure it's a valid question (unlike 'my friend told me coffee gave her warts, is this true?').
fredley
CC BY-SA 3.0
2015-02-09T13:35:02.677Z
It's there in the question description. Primary articles for verification and a search link if you want to obsess over it. ;)
qedk
CC BY-SA 3.0
2015-02-09T13:36:06.043Z
@TomMedley, I'm a Wikipedia user and I'm used to verifying every claim I make when  I add content. I do the same on Coffee.SE.
qedk
<caffeine><health>
Does coffee really reduce the risk of Alzheimer's?
qedk
# Does coffee really reduce the risk of Alzheimer's?

(Asked by: username_0 on 2015-02-09)

Many medical websites suggest so. If yes, then how? Alzheimer's is primarily incurable but then it can be delayed, how can coffee play a role?

References:

* [Pubmed - Caffeine as a protective factor in dementia and Alzheimer's disease](http://www.ncbi.nlm.nih.gov/pubmed/20182054)
* [Medical Daily - Drinking Coffee Can Lower Alzheimer's Risk By 20%, All It Takes Is 3 Cups A Day](http://www.medicaldaily.com/drinking-coffee-can-lower-alzheimers-risk-20-all-it-takes-3-cups-day-312410)
* [Alzheimers.org - Drinking coffee reduces your risk of dementia, says study](http://www.alzheimers.org.uk/site/scripts/news_article.php?newsID=1223)

**Tags:** caffeine, health

> **Comments:**
> **username_1**: Can you link to somewhere that makes the claim?  
> **username_0**: Google Search Link: http://goo.gl/78hWjL  
> **username_1**: Sorry, I didn't mean in general, I meant the specific ones you had found. On Skeptics, where they get a lot of questions like this, all questions must be backed up with sources. Although we probably wouldn't need a strict policy here, it's still good to prompt for such information on questions like this to make sure it's a valid question (unlike 'my friend told me coffee gave her warts, is this true?').  
> **username_0**: It's there in the question description. Primary articles for verification and a search link if you want to obsess over it. ;)  
> **username_0**: @TomMedley, I'm a Wikipedia user and I'm used to verifying every claim I make when  I add content. I do the same on Coffee.SE.  

---

## 1 answers

### Answer by username_1 on 2015-02-09. Score: 4 | Accepted answer

## tl;dr: Not sure yet, but it looks promising

---

So there are a [whole bunch](https://scholar.google.co.uk/scholar?hl=en&q=coffee+alzheimers&btnG=&as_sdt=1%2C5&as_sdtp=) of studies that have been done that have investigated a potential link between coffee consumption and Alzheimers.

The problem, as always, is that these types of '[cohort studies](https://en.wikipedia.org/wiki/Cohort_study)' are really difficult. Basically the way it works is:

* Get a load of volunteers
* By doing questionnaires, work out everything about them
* Track them over a long period of time
* See if there's a statistically significant link between combinations of behaviours (such as drinking coffee) and a particular outcome (diagnosis of Alzheimers)

All the standard stuff applies here: you are not testing for *causation*, only for *correlation*. For example, ~80% of Americans drink coffee, but in other cultures this number varies a lot. If the coffee drinkers in your study are predominantly American, and the non-coffee drinkers are predominantly not, you have a whole bunch of confounding factors. Designing your study to avoid this kind of situation is really hard, especially when you're relying on volunteers.

There's also the issue of what exactly are you measuring? Someone might drink 3 cups a day now, but only has done for the past few years. Another person might drink 2 cups a day, but has done their whole life. Another person might drink 2 cups of decaff a day. Questionnaires are usually not sophisticated enough to capture this level of detail (partly because in your big expensive study you want to capture as much information about different behaviours as possible - not just coffee consumption).

Remember also that medical studies are *chronically* badly reported in the mainstream press. Even in 'high-brow' publications, by the time the headline-writers get their hands on a study, the message can have changed *wildly*. It's always worth trying to dig up the actual paper whenever new research is mentioned in the news. If no paper is linked, just ignore the headline.

One tool against all of this uncertainty is [meta-analysis](https://en.wikipedia.org/wiki/Meta_analysis). This is where you look at every single study, weighted by how confident you are in the data (e.g. by weighting more to studies with more participants, and better questionnaires etc.). You then do some careful statistics work to get a measure of confidence across all of the studies. Think of it as a sophisticated way of 'averaging them out'.

[One of these was done](http://www.maneyonline.com/doi/abs/10.1179/174313206X152546) in 2002. Only 4 studies had been done by then, but the conclusion was:

> Although our pooled estimates show that coffee consumption is inversely associated with the risk of AD, the four studies had heterogeneous methodologies and results. Further prospective studies evaluating the association between coffee consumption and AD are strongly needed.

(Heterogeneous is science for 'different')

i.e., "Not sure yet, not enough data, but it looks promising, give us more money for research."


---

