Correlation is not causation anyway. It has not been proved benzodiazepines actually increase the risk of dementia, or whether people with early, undiagnosed dementia are simply more likely to present with symptoms for which benzo’s are prescribed.
As they’re commonly prescribed for sleeplessness and/or agitation, which are both associated with dementia, my money’s on the latter.
I think people with early dementia may be approaching their doctors with problems years before anything is formally diagnosed - and walking away with prescriptions for benzodiazepines.
I think it has something in common with MS, in that people may already have had it several years, and sought treatment for symptoms, before it’s diagnosed.
A friend was diagnosed a couple of years ago (with dementia, I mean, not MS), and in retrospect, the signs had been there, but nothing very drastic. She’d always been a bit self-absorbed, so when she didn’t remember things I’d said (sometimes quite big things, like losing my job, or having an accident that put me in A&E), I rather unkindly suspected her of not listening.
I didn’t think: “Oh dear, she might have dementia”, because you just don’t! So I reckon it was a good few years she’d been having symptoms, before they got bad enough to prompt investigation.