Thread by @GidMK

This study has gone a bit viral because apparently puppies are going to save our lives

Sadly, that's pretty unlikely to be true 🐶🐶🐶

https://twitter.com/CNN/status/1181558654044119041

I should stay at the start - dogs are amazing, we don't deserve their love

BUT

Facts are still important

Study is here: ahajournals.org/doi/10.1161/CI…

The researchers did what's know as a systematic review and meta-analysis, looking at all of the studies on dog ownership and health that they could find

They then pooled the numbers from all of these studies into a meta-analysis, which showed that owning a dog was associated with a 24% decreased risk of death, overall

So why am I not going out to corral every dog I can find?

Well, there were a few significant issues with the study

First up, we have what's known as statistical heterogeneity

Basically, this means that the studies that the researchers found and analyzed together were very different, making the analysis less reliable

How different were these studies?

Well, a commonly-used measure to assess heterogeneity is the I^2 statistic. A value between 0-50% is considered "low"

This study found I^2 between 96-98% (except for one subgroup analysis)

This makes sense, because the studies that they found were VERY DIFFERENT

For example, one study looked at ~everyone in Sweden~, while another looked only at elderly women with hypertension

But that wasn't the biggest issue

The biggest issue was that this piece of research didn't look at confounding factors

At all

Now, I bang on about observational research and the problems with causality, but that's usually in well-controlled studies where residual confounding might potentially be an issue

Here, we have a piece of research that didn't control for any factors other than dog ownership ~at all~

It's not hard to see how this might make the results a bit problematic

Essentially, it means that this study just looked at a simple association

Dog owners die a bit less than non-owners

That's it!

Dog owners are often very different to non-owners in important ways

From the Swedish study I mentioned above, owners were more educated, married more often, more likely to have kids, etc

What this means is that there are literally hundreds of explanations for dog owners being more healthy than non-owners that have nothing to do with the dogs

Funnily enough, that's something that the authors noted in the study

Basically, healthy people might be more likely to buy dogs

Thus, dog owners die less

Association rather than causation

And the mechanisms of dogs saving our lives are a bit flimsy. Some minor reductions in blood pressure =/= lifesaving

So...puppies probably aren't saving our lives

They're still great tho, you should definitely get one

Adopt, don't shop!