My understanding is that there are literally hundreds of qualified, passionate applicants for each spot. I've met a few. If we are spending billions of dollars to strap that particular person to a rocket, I think humanity should be able to benefit as much as possible. I don't think its unreasonable to have as a requirement for that service that certain health records might not remain private. Just like it would not be unreasonable to require certain high level public servants to divulge their tax records, as long as it was understood as a requirement beforehand.