You're 24 years old and you're having trouble remembering names and movie plots.
It's slightly troubling, but you pass it off to having millions of impressions and images bombard your brain every day.
After all, you're too young to have Alzheimer's - right?
Maybe not.
If you're white, you probably have the gene that increases your risk of developing Alzheimer's disease (AD).
Pretty scary stuff.
That's not all the bad news. This gene starts doing its damage decades before AD reveals its ugliest sides, even though symptoms don't show up...