The idea that statins have a causal relationship to memory loss is a popular bit of folklore. The idea that statins prevent memory loss has been reported in medical journals. AFAIK, all controlled studies suggest no relationship whatsoever. Here's an even handed discussion:

https://www.healthline.com/health/high-cholesterol/link-between-statins-and-memory-loss

Basically what it says is that there's no evidence of cause and effect, but check with your doctor if you're worried:

"The researchers found no evidence that using statins caused memory loss or dementia. In fact, there was some evidence that long-term statin use may protect against dementia.
Scientists believe this is because certain types of dementia are caused by small blockages in blood vessels that carry blood to the brain. Statins may help to reduce these blockages.
There remains some uncertainty about whether statins affect memory.
A 2015 study found that a small group of patients taking statins experienced amnesia. However, that finding may have been insignificant. The percentage of people taking statins who reported memory issues wasn’t much different from those taking other cholesterol-lowering medications.
Despite the large amount of research showing that statins do not cause memory loss, some people may still experience this condition. Talk to your doctor if you are taking statins and experiencing unpleasant side effects. You should not stop taking the medication on your own."

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