Your age group, sex, location, profession/industry, income estimation - you can assume they have this data.
That + a few data points that could be tracked by apps or websites:
- Searched online for symptoms
- Searched for doctors
- Called the clinic to schedule an appointment
- GPS to the clinic
- Connected to the clinic’s WiFi
- Doctor is a specialist in X
Cross some of that, personal info, and ads of treatments for conditions of X.
They don’t need to listen to your mic.
That said, if it’s a fairly common condition, it might be the case you were presented the ad before and never noticed it.
it’s like CSV, but larger and keeps you awake at night