Thread by @GidMK

Oh god, it's happening again

That's not what this study found, it's not true, moderate drinking isn't good for you 1/

https://twitter.com/BIAUS/status/1032062702124818433

The study that's being reported here is a meta-analysis of 6 different observational trials looking at drinking habits in England and France 2/

This means that the researchers combined the data from 6 studies into one big analysis, and looked at the associations between drinking and heart disease 3/

You can find the study here: bmcmedicine.biomedcentral.com/articles/10.11…

What has previous research shown on this topic? Well, if you look at observational trials done in the last few years, you find a wildly mixed bag 4/

I've written about this before. Essentially, depending on the number of confounding variables you control for, you either find moderate drinking to be protective or causative for heart disease 5/ medium.com/@gidmk/the-myt…

Back to the study at hand. The researchers looked at moderate drinking and chronic heart disease, as well as heart disease deaths, in an observational trial. They controlled for only a few confounders in their analysis. Do you think they found moderate drinking to be: 6/

Bit of an easy question there: moderate drinking was associated with a lower risk of heart disease and cardiovascular mortality. Not surprising 7/

But what about HEAVY drinkers? People who had more than 21 standard drinks per week? Protective or causative of heart disease? 8/

Now, see, this should be easy too. Prior research has consistently shown that, above a fairly low threshold (1-2 drinks per day), drinking is terrible for your heart

But guess what? This study found the opposite!

Heavy drinking was associated with the same reduced risk as moderate drinking

In fact, the only groups that this study found to be at greater risk of heart disease were never-drinkers and former drinkers

Weird, that

It's easy to see why people who used to drink might be worse off - they are likely former alcoholics in recovery

But what about consistent non-drinkers?

There are a few possibilities:

1. Former alcoholics who misreported their drinking status
2. Unhealthy people (i.e. chronic liver disease) who don't drink for that reason
3. Unable to afford alcohol, and likely less well off
4. Rare non-health-related-abstainer

But, I digress (and also messed up my threading somewhere)

I was talking about heavy drinkers. What could possibly make them healthier?

If you have a look at this table of demographics, it'll give you a massive hint:

Yes, it appears that social factors are almost certainly to blame. If you compare the former/never drinkers with everyone else, they are older, fatter, and poorer

What this means is that there are likely many confounding variables that this observational research did not pick up on, what's known as residual confounding

Since this study was a bunched-together analysis of several observational studies, there are always going to be factors that could not be included in the analysis

And, to their credit, the authors acknowledge this cheerfully:

In fact, the authors recommend caution generally, because of the weird association with heavy drinking that they found

The other thing to note is that, while the hazard ratios look impressive (50% more heart disease in the non-drinkers!), the absolute risk differences were very small - between 1 and 2 percent

So

Moderate drinking isn't good for you

This study found a weak and strange association between drinking and a reduced risk of heart disease

It is ALMOST CERTAINLY explained by social differences between the groups they looked at

What's even worse, the main finding of the study wasn't even about moderate drinking per se. The authors were really looking at whether INCONSISTENT - i.e. heavy/moderate/heavy/light - drinking was problematic

And they found that it was

Now, this finding suffers from the same issues as the other ones, but still, that's a really interesting result that deserves further investigation

Not at all "Moderate drinking is good for you"

Bottom line: moderate drinking is almost certainly harmful to your health

Don't drink to be healthy, because it isn't

That's not a great story, but it's the truth

Also, as has been pointed out, heavy drinking is DEFINITELY BAD FOR YOU

21+ drinks a week (3+ bottles of wine) is bad, don't do it, get help if you need it to stop