Shingles Vaccine Protects Against Dementia, But How Strong Is the Effect?

Here’s my attempt to decode it.

Causal evidence is hard to come by.

It usually takes a randomized clinical trial (RCT) to demonstrate cause and effect, especially involving medical interventions. RCTs work because randomization evenly distributes the countless number of variables between individuals into the experimental and control groups, ensuring that the results seen are strictly due to the intervention.

But sometimes, we don’t need RCTs to demonstrate causality.

Sometimes, we can capitalize on existing systems to do so.

This is what three studies from the UK, the US, and Australia have done during the past year. They provide sufficient evidence to show in a causative manner that the shingles vaccine protects against dementia.

But the effect size exactly was unclear in these studies. After a deep dive and thought, here’s my attempt to pinpoint the effect size to infer insights on their real-world impact in the battle against dementia.

Study 1: Eyting et al. (2023), The U.K.

(I wrote about this study in “An Unexpected Ally In Dementia Prevention: Shingles Vaccination.” But I’ll describe it again…