[meatmanek]

They weren't measuring the effect of getting the vaccine directly, just the effect of being eligible for the vaccine. That is, they looked at rates of dementia by birthdate cohorts, not by got-the-shingles-vaccine cohorts.

If your hypothesis were correct, the vaccinated cohorts would have lower-than-population-average dementia rates, while the unvaccinated cohorts would have higher-than-population-average dementia rates. This wouldn't cause any measurable effect on the total dementia rate for a given birthdate, as presumably something like 47.2% of the population born just before Sept 2, 1933 would _also_ be doing lots of health things right.

That is, your hypothesis doesn't explain the data they found, which is not categorized by vaccination status, and showed that people born just after Sept 2, 1933 are significantly less likely to be diagnosed with dementia than those born just before Sept 2, 1933.

[telebell]

Oh I see. Hmm, it’s interesting although the effect seems small enough that I wonder if the true cause is something like “if you get a serious illness as a senior then you’re more likely to decline overall and that’s what contributes to Alzheimer’s.” Since Alzheimer’s also seems correlated with lots of other bad conditions, like T2D, sedentariness, low physical fitness, poor social habits, smoking.