Understanding 分かる in this sentence


> 警察庁によると、このテストで「認知症」という脳の病気の可能性があると言われた人は約１年で５万７０９９人いました。
> **そして、この中の１８９２人が、医者が調べて認知症だとわかりました。**  
>  According to the police, in this test, in around 1 year, there were 57099
> people who were told that they might have a brain disease called dementia.
> 1892 of these people _knew they had dementia because a doctor had tested
> them_.

I'm having trouble understanding the sentence in bold. The translation is my
best guess. My understanding of 分かる is a bit shaky. Does this sentence suggest
that the 1892 people already knew they had dementia **before** they took the
police test, or does it imply that those people went to the doctor **after**
the police test and were then confirmed as having dementia? (putting aside the
fact that a person diagnosed with dementia might still not _know_ they have
dementia).




This わかる is close to 判明する(become clear) rather than "know". So
この中の１８９２人が、医者が調べて認知症だとわかりました means "It became clear that 1892 of these people
had dementia because a doctor had tested them."

We can't know why they took police test and when they knew they had dementia
just from this sentence.




This わかる is close to 判明する(become clear) rather than "know". So
この中の１８９２人が、医者が調べて認知症だとわかりました means "It became clear that 1892 of these people
had dementia because a doctor had tested them."

We can't know why they took police test and when they knew they had dementia
just from this sentence.

