Coffee Drinking Reduces All Causes of Death According to Recent Meta-Analysis Study
Introduction
Last year I made a post on "The Health Benefits of Coffee".
As I did not have academic access to view full papers at the time this was based on a combination of abstracts, a Medscape presentation (by Dr Bret S. Stetka) and my own notes.
Shortly after my post a new meta-analysis on Coffee and Mortality by Giuseppe et. al was released but I had no means of legally accessing it.
Luckily I have found a subscription service called DeepDyve that allows access to selected journals for a monthly fee and they have the study!
It is called :
I would like to summarise and discuss the findings which I think will be of interest to those of us who are coffee lovers.
I will try to keep it brief!
Before We Start: Meta-Analysis - What is it and Why Should We Care?
A meta-analysis is a type of study that combines the results of multiple studies.
The basic theory is that by combining lots of smaller data sets you can derive a larger data set for statistical analysis, thereby improving the validity of your results.
Sample size is one of the frequent issues in certain types of scientific research. Meta-analyses allow you to simulate a larger sample size than you would otherwise have available to you.
There are some problems with this approach but the TLDR is that in theory a meta-analysis gives you more "bang for your buck" using existing data than those single studies on their own.
The Findings - A TLDR Summary
Drinking 4 cups of coffee per day REDUCES:
- All cause mortality (i.e. death from all causes) with a RR (Relative Risk see explanation below) of 0.84
- CVD (Cardiovascular Disease) mortality with a RR of 0.83
- CHD (Coronary Heart Disease) mortality with a RR of 0.84
- Stroke mortality with a RR of 0.72
NB: Figures are taken from the raw data in the author's tables (2 and 3) for the RR of drinking 4 cups of coffee, rather than the up to 4 cups of coffee measure in the abstract as I could not find the full comparative data for the latter measurement.
Cancer Mortality Results, Smoking vs Non Smoking
However 4 cups of coffee slightly increases Cancer Mortality with a RR of 1.01 - this is believed to be an artifact of the association between smoking and coffee drinking:
Excluding Smokers Seems to Restore the Pattern
Considering non-smokers ONLY reduction in mortality seems to be consistent with the other results, in that 4 cups per day reduces mortality due to Cancer with a RR of 0.9.
Quick Explanation of RR/Relative Risk
This is a measure that is used to give a probability for something occurring.
For example when we say that 4 cups of coffee reduce all cause mortality/death with a RR of 0.84 it means that compared to someone who drinks no coffee you have only 84% of the risk of death.
So 4 cups of coffee per day reduce your risk of death by 16%.
Summary of Methods
Studies were found using electronic databases i.e. PubMed, EMBASE.
I personally use PubMed as it is publicly available for free. I believe EMBASE requires a subscription.
The Inclusion Criteria for studies were:
- Prospective design - i.e. the study followed people over time, rather than looking back at historical data.
- Evaluated association between coffee drinking and mortality - obviously since this is what it is trying to study!
- Assessing and reporting of Hazard Ratios and 95% Confidence Intervals for mortality > 3 exposure categories - a minimum baseline needed to be set to allow proper comparison.
- Studies provided data on the number of coffee cups consumed.
The Exclusion Criteria for studies were:
- Insufficient Reported Statistics - rather obvious reasons!
- Assessed Composite Outcome - the meaning is not clear in the paper (to me at least). I think they are referring to a lack of a clear outcome in e.g. rather than specifying death by CVD, a study may cite an even like MI(heart attack).
- Where more than one study or result came from the same cohort (group) of people studied, only the study with the entire cohort and/or longest follow up was used.
Sampling Data:
- 470 studies screened but only 31 Studies were used, with smaller samples for specific causes of mortality (see table).
- It is common to exclude studies based on various criteria, see discussion later.
- 1.6 million participants.
- 183,991 total deaths (all causes).
- 34,574 CVD deaths.
- 40,991 Cancer deaths.
Discussion
Overall the inclusion and exclusion criteria make sense. Due to the nature of how meta-analyses work it is uncommon for any two studies to be exactly identical.
The inclusion and exclusion criteria enable a certain degree of uniformity between the studies that you use.
Further although 31 studies were used in total it should be noted that different numbers of studies were used for analysis of each form of death.
This is because not every study used looked at every form of death we are considering here.
I have constructed a quick table to summarise this:
The Number of Studies Used For Each Mortality Type
| Mortality | No. of Studies Used | No. of Deaths | Total Sample Size |
|---|---|---|---|
| All cause | 24 | 183,991 | ? |
| CVD | 23 | 34,574 | ? |
| CHD | 12 | ? | ? |
| Stroke | 9 | ? | ? |
| Cancer | 15 | 40,991 | ? |
Unfortunately I did not find a summary of the (death) sample sizes that this breakdown represented beyond the figures already stated for all cause, CVD and cancer.
Further we do not know the TOTAL sample sizes (people who lived and died) for each form of death.
For example the total sample size of 1.6 million participants represents all 31 studies used, but none of the mortality samples use all 31 studies (e.g. all cause only uses data from 24 studies).
The authors have published a huge multi-table analysis which includes every study but does not include separate stroke/CHD data.
I suspect the lack of data for Stroke and CHD is due to lack of space but there may be other reasons.
Having specific sample sizes may have provided some additional useful information.
Further the large discrepancy between the sample for all cause mortality and the other causes that are listed is likely down to some of the studies only noting mortality rather than specific causes.
Geographic Breakdown of the Studies
| Location | No. of Studies |
|---|---|
| Europe | 14 |
| USA | 11 |
| Asia | 7 |
As we can see the distribution of studies varied geographically in a non uniform manner i.e. the majority were in Europe and the USA.
This could cause distortion of results due to variation in environmental and genetic factors.
It would be useful to be able to see if there was a difference in RR based on geographical location.
The authors do briefly mention this in their discussion.
Smoking
The issue of smoking and not smoking seems to have a massive effect on the benefits of coffee drinking as it applies to cancer mortality risk.
It would seem that adding coffee drinking may actually increase your risk of developing cancer if you also smoke.
This is contrary to the finding of decreases in mortality from the other causes that are noted in smoking.
Figure 3 illustrates these points very well in graphic form:
Before we get too excited with these results we should note that some of the previous caveats in terms of sampling apply here.
The data considered for smoking and non smoking is considerably smaller in terms of number of studies. I have summarised this in the table below:
Studies Used for Comparing Smoking and Non Smoking
| Mortality | Smoking (n=studies) | Non Smoking (n=studies) |
|---|---|---|
| All cause | 5 | 5 |
| CVD | 4 | 5 |
| CHD | 2 | 3 |
| Stroke | 2 | 3 |
| Cancer | 4 | 5 |
The smaller number of studies highlights an important problem with meta-analyses, that of failing to control for confounding factors.
The vast majority of the studies used did not differentiate between smokers and non smokers.
Even those that did may not have done so adequately and that may be responsible for the discrepancy between the number of studies examined for smokers vs non-smokers.
This inevitably reduces the statistical strength of the findings in this specific instance.
Meta-analyses are a fantastic tool but they are not perfect. A well designed study of equivalent size could in theory give you more statistically valid results.
Unfortunately money, time and other resource limitations mean that in most cases that is an impossible dream to achieve.
Why Would Coffee Increase Cancer in Smokers But Reduce it in Non-Smokers?
As to why smoking would seem to not only negate the benefits of coffee in relation to cancer but actually cause a reversal it is hard to say without more information.
One hypothesis I can think of is that drinking hot drinks may irritate the oesophagus (gullet).
In normal individuals this may not have as significant effect but in smokers they may already have an existing irritation of the oesophagus as a result of smoking.
This may result in a greater sensitivity to developing oesophageal cancers.
Further there may be some as yet unknown interaction between smoking and coffee that has a carcinogenic effect in combination.
It would be interesting to see if the higher risk in smokers translates to cancers in general or a specfic subset such as oesophageal cancers.
Conclusion
This is a fascinating study which supports the growing body of evidence that coffee is good for us.
As I have discussed there are some problems with the data and these are common issues with meta analyses.
I don't believe that these should detract from the main finding that coffee drinking reduces mortality from all causes.
When it comes to smoking and coffee drinking (in relation to cancer mortality) I think we need a lot more research before we can say what is going on with any degree of certainty.
If I was a smoker I wouldn't give up coffee drinking but would use it as an excuse to try to stop smoking.
Although the cancer risk seems to increase according to these results there are other benefits such as to CVD health that are maintained in smokers.
I suppose it depends on what method of death you fear more.
Anyway I don't need an excuse to continue enjoying my coffee drinking!
References
- Grosso, Giuseppe, Agnieszka Micek, Justyna Godos, Salvatore Sciacca, Andrzej Pajak, Miguel A. Martínez-González, Edward L. Giovannucci, and Fabio Galvano. 2016. “Coffee Consumption and Risk of All-Cause, Cardiovascular, and Cancer Mortality in Smokers and Non-Smokers: A Dose-Response Meta-Analysis.” European Journal of Epidemiology 31 (12): 1191–1205.
Thank you for reading
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Tables were constructed by msyself using the data in the paper. Figure 3 was taken from the paper an all uncredited images are taken from my personal Thinkstock Photography account. More information can be provided on request.
This is a great read. Very interesting stuff. I am a coffee lover so it makes me very happy to read this.
Are there any studies that are anti coffee or ones that emphasise the negative effects or are there any negative effects in general? (apart from the slightly increased risk of cancer in smokers)
just gave my 2 cents on that , some negative effects of coffee, increasing recovery time, the obvious regression in terms of daily usage and effect and the health "benefits" of drinking a highly stimulating and acidic substance.
Just done some reads you might find interesting
What you didn't know about coffee: Asher Yaron at TEDxUbud
If anything watch the video , the others are just data , the video has a different mindset within
If anyone wants to watch hours of TED's and give e the summarized version I would love to hear it I'm tired of reading o this topic :D here is the last thing I couldn't get through :)
http://sprudge.com/the-7-greatest-ted-coffee-moments-in-history-41002.html
Should I make a post ? on coffeee :) maybe a in-depth look from my perspective :) ?
I think there are old studies that used to suggest this but one of the criticisms was the usual thing of them not controlling sufficiently for confounding factors. Some of them also extrapolated animal research on caffeine (on it's own) rather than actual coffee which is obviously problematic. I don't know of any recent ones though.
@thecryptofiend I'd love to share a cup with you - black or with milk and sugar? but we drink in moderation okay? always in moderation :)
these guys, too
He was ...
this one went to the coffee shop and got high
hahahha
Lol super cute!
That's very interesting.
For sure. Confounding variables and extrapolating animal studies always need to be carefully considered. Further a pure component like caffeine may have totally different effects than a complex mixture of compounds like coffee.
Especially if that complex mixture includes lots of sugar and cream :)
Would be interesting to compare the results with black coffee vs coffee with cream and sugar.
4 cups of coffee a day...if I drank 4 cups of coffee a day I'd need to smoke 10 times as much shatter just to get to sleep at night...I've no doubt it reduces mortality rates, especially with those consumption rates...I'm guessing several of the study subjects were actually dead, they just couldn't close their eyes because the caffeine overdose...LOL
On a serious note tho...interesting read...I can see where coffee could be beneficial health-wise and although I can't drink more than a cup a day without literally losing sleep, it has to be far better for people than those chemically laced energy drinks!
I'm the same as you, even green tea keeps me awake.
I read on some alternative medicine website, vitamin doctor, or something, that people hypersensitive to caffeine should mostly avoid it because if they have it regularly, over a life-time, it can cause dementia, depression and alcohol cravings!
I have no clue how true any of that is but it's probably not worth the risk, I guess our bodies our telling us not too!
Edit: oo! decaff sounds good!
I drink a cup a day...it helps me get out of bed...and I used to drink it throughout the day, but I've aged a bit and can no longer keep the hours my younger version did...that's really the reason I don't drink it more...One cup before noon and I'm fine...2 cups, or any caffeine after noon, and I toss and turn all night...go figure.
Some people are more sensitive to the stimulant effects due differing abilities to metabolise caffeine.
The research that I have seen suggests the opposite. Caffeine probably reduces dementia and depression risk. I've never hear of any alcohol cravings association. I would not take that website too seriously because I suspect they were trying to sell you something else.
Caffeine is clearly not healthy. You can find alcohol might lower blood sugar or kill viruses but this doesn't mean it's good for the liver or that it will be healthy. Caffeine raises blood pressure which increases heart attack or stroke risk, and it decreases insulin sensitivity. It is true not everyone has the genes or diet to be at risk of heart attack, stroke, or diabetes, but it is something some people or most people do have to be concerned about.
References
Based on what? Your personal conviction? Whilst we agree on many things we will not on this. I don't necessarily think that caffeine is wonderful (particularly taken on it's own) - the evidence supports that it is perfectly safe as part of coffee drinking
I posted that the healthy component in coffee can be isolated but the unhealthy caffeine is the junk part of coffee. A pill can contain only the healthy part and then a proper study can be conducted but you cannot take this study as proving coffee is healthy.
Not being associated with negative outcomes is not the same as being the cause of good health. A proper study would look at each component or constituent in coffee one by one to determine if any of them increase the lifespan of rats or have some positive health benefit in an animal model and eventually a human trial. If a human trials shows something then I believe it if it's a proper randomized controlled study.
Reference
http://www.medicinenet.com/script/main/art.asp?articlekey=39532
It is not quite that simple though. Caffeine may have benefits too. Most agents have can have both benefits and disadvantages. You believe that caffeine is bad and so are picking and choosing evidence that supports that assertion. It may well turn out that coffee is healthier without the caffeine being in it. Right now we don't know though so I am not going to make that assertion.
On caffeine you are correct I believe the negatives far outweigh the positives for most people. Just as with alcohol or sugar. Yes you can consume these things but most people will have long term side effects from over consumption.
In the USA obesity is a problem. In the USA diabetes is common and metabolic syndrome is a problem. It is known that sugar and caffeine can make those problems worse. So if a person can avoid caffeine, and sugar, and alcohol, then it would probably be beneficial.
Does this mean 100% of everyone has to eliminate that? No. It means people who have the genetics to be concerned about diabetes, or alcoholism, or who are overweight, probably should avoid it.
And we do know that coffee without caffeine is healthier because as I said the component in coffee which is associated with the health benefit has been found. I cited a source to that as well so just isolate that compound and why do you even need caffeine or coffee?
That is still far from certain. Like I said without further research we can't say that.
Okay so we need a study which compares the effect of coffee vs the effect of the isolated chlorogenic acid? Cool. If the study were to show coffee is producing a better measurable effect my opinion would have to change but right now we have no such study so your jump to the conclusion that coffee is healthy is a leap of faith.
We already have the studies that show that coffee is beneficial so your "leap of faith" assertion makes no sense. Indeed it is you who are using faith to judge that anything with caffeine in it must be harmful.
Yes the extra information would be useful and we might find out that cholorogenic acid is even better but that bears no relation to this meta-analysis.
Further if we had research comparing decaffeinated coffee with regular coffee we might also find that was healthier but that does not change the findings here.
Just because one component of coffee is more or less healthy does not reverse the original conclusion.
Let's just leave it there because we are not going to agree on this.
Can you link to a study which is proper, randomized controlled with either an animal model or human trials? I don't think the studies you present are clear at all in showing coffee to be healthy.
I would be satisfied if you can show a rat study where there are controls and rats given coffee. Then we see which rats develop diseases and which rats live longer.
I think they are. That is the end of the matter for me until we get more research.
I am not here to satisfy you or not satisfy you. The evidence has been presented whether you accept it or not is up to you.
I also find it rather strange that you are arguing about the validity of studies which do involve humans but then state that you would be happy to use animal based models.
That makes no sense. Animal studies don't always directly translate to humans so your reasoning is once again inconsistent there.
Further I suspect that no matter what evidence were presented it would not change your opinion which seems from the discussion here to be entirely fixed.
If you think the current research is of poor quality and inadequate you are free to do or fund your own research of a higher quality and get it it published in a peer review journal.
That is the end of the matter from my stand point and I am frankly tired of talking around in circles with you because you have made it patently clear you don't know what you are talking about when it comes to medical research.
It gets us nowhere and frankly I have better things to do.
I guess hypersensitive people can't metabolise caffeine properly because it's definitely in their system for a ridiculously long time. So you could both be right. I think they mostly sell books about vitamins, not sure it was years ago that I went on the site.
Lol I know the kind of site!
For sure! I think the main benefit is not from the actual caffeine but various compounds know as polyphenols. I summarised some of that in my original post about coffee. So you may get most of the benefits by drinking decaff too.
Hmmm...I'll hafta look into that...I always thought decaf was just nasty water...LOL
It might taste like it lol!
Very interesting article/post. I'm a kind-of-heavy coffee drinker and a moderate smoker. Smoking I intent to quite in a month and was also thinking of quiting coffee (coffee can give me headages on days I do not drink coffee). But maybe, based on the results of this post, I should continue drinking coffee. Will do more research myself, your article is a great start for that.
Thank you:) Good luck with the smoking I hope you succeed.
Thanks! :)
I have an 8 cup a day habit. Yum!
I have a about 6!
That means you are also a professional!!
Lol. I have cut down - I used to drink 20 a day sometimes when I was working in surgery - it used to help me keep going! I don't thing that would be good long term though.
wow , I was having issues with drinking 8 hours a day around 2-3 cups of lots of milky sugary coffee
It depends how fast you build it up. If you do it gradually then you are less likely to have problems. There is no reason to drink more than 4 cups unless you really love coffee.
:D Lone starrrr GUrrrrr ! HOt HOT HOT :D , best scenes , best parody , great movie , it's like a trilogy in one :)
Awesome!
sips coffee
Lol:)
Remembers the existence of his existential crises that he now has to spend an eternity with due to his coffee induced immortality
Oh, man..
Now that's funny!
:)
It is important to note that this study is not saying coffee is healthy, or that it "reduces" or "increases" anything specific which would directly influence mortality. More than likely this was funded by individuals who want to promote drinking coffee but it should be noted that this sort of study is non-specific and not very useful for determining the health benefit of coffee.
Milk has also been studied in a similar way. The difference is with diary we know that it is insulinogenic and high insulin levels are associated with or may eb a cause for CVD and metabolic syndrome. All Cause Death studies do not indicate that something is healthy. To find any health benefit in coffee the specific component would have to be isolated into a pill form and that pill would have to be associated with longer lifespan at least in rats.
According to my own studies I suspect chlorogenic acid is the only healthy part of coffee. The caffeine isn't healthy because it decreases insulin sensitivity and raises blood pressure. The coffee you drink also stains your teeth. So the only thing in it which I found which has any positive benefit is chlorogenic acid which may be possible to take in a pill form without the negative health risks of coffee itself.
Reference
https://examine.com/supplements/chlorogenic-acid/
Yes we all know you are anti-coffee. This study is consistent with previous findings.
I'm not anti or pro-coffee. I am only saying this study you present does not prove coffee is healthy. It could be true that there is something healthy in coffee but we also know for a fact caffeine is unhealthy and also in coffee. This is similar to the studies saying "drink beer because beer drinkers live longer" or "drink wine because wine drinkers live longer" and there is something healthy (hops) and (grape skins, grape seed) in wine which shows it does have health benefits but it doesn't mean it's wine. It's the grape skin, the hops, the grape seed, which is beneficial, and then alcoholics may use it as an excuse to drink lots of wine.
The truth is, you only need reversatrol (which I use myself sometimes) or pterostilbene. You don't need to accept the risk of alcohol (alcoholism, liver disease, weight gain) just to get the benefits. Same with whatever is in coffee, you don't actually need to drink coffee to take a pill giving you more of the benefit than if you drank 100 cups of coffee a day.
I am pro health. I think if you can get the same benefit with less risk why not? In the case of a pill you can get 100 times the benefit with way less risk because you don't need the caffeine at all. There are also pro cannabis studies and while I agree there are healthy parts of cannabis I would not say smoking weed is healthy because smoking is never healthy.
How do you know that? I'm not saying that is wrong but that is not based on evidence. When I see the evidence I will make the decision.
There is no truth in science. Only the body of the research. I have been interested in resveratrol for some time due to it's life extension potential. Sadly the evidence is at best contradictory right now so we don't know for sure.
People can take cannabis without smoking though.
Everything I said is based on the evidence I've studied. Just like what you say is based on the evidence you have studied. On coffee there is no study where an animal model such as rats have been given coffee with or without caffeine compared to a control to see if it extends lifespan. Show me that study to convince me of a measurable health benefit.
People can take cannabis without smoking. People can take whatever is in coffee without caffeine. The beneficial part of cannabis has been isolated. Find and isolate the beneficial part of coffee and do trials with that to convince me that something in coffee is beneficial.
Exactly my point. We don't know. Further the only way to know for sure would be to actually do it as a human study not on animals. We do have the data for coffee, hence we cans say that coffee has benefits.
Really?
You speak in absolute certainties. That is not scientific and it is not how research works.
Better still why don't you do the same and prove that it is harmful? You seem to be absolutely certain of that with a religious zeal.
Great post as always thank you
You're welcome thanks for your support!
Great read. Coffee is my all time comfort.
Cool glad you liked it. I love coffee too!
good,
I like it
Thanks:)
As I sat reading with a cup of coffee, all I can say is that I will be continuing this morning regime...thanks for giving me more reason!
You're welcome. I will be doing the same!