Since the recent discoveries about Shingles Vaccine delaying dementia https://hsph.harvard.edu/news/link-between-shingles-vaccine-...

One of interesting checks in this study might be to check when (if) any of the participants had taken this vax and what the impact might be on an Alzimer's diagnosis.

Purely anecdotal, but I witnessed a person starting to experience a severe cognitive decline right after the two doses of the Shingles Vaccine. It can surely be a coincidence, but I was very surprised when I read about this study.