Are these phone calls from Mayo Clinic? My experience is that when Mayo Clinic is interested in inviting me to participate in a study they use my email address. I have never received a phone call like that from Mayo Clinic. I'd be suspicious of a scam if I received a phone call from any place asking for my participation in a research study. I couldn't say how a hacker gets medical information but I wouldn't tell them anything over the phone and would just hang up.