Your question is quite specific and I might not be the best person to answer it. You are talking about groups of individuals who are sicker than others and I am finding it hard to continue on this topic. I remember seeing statistics about this, but I would be afraid of misquoting them.
I can tell you that people in Émilie's age group rarely get cancer and that they usually overcome it. Unfortunately, I cannot give you the actual statistics. I can only tell you about Émilie's case.
Getting back to the idea of insurance against an unknown risk, you are right. Yet we also have to agree that there are steady advances in medicine, which also reduce the person's absence from work, allow them to return and give them hope of recovering thanks to new medications, new approaches and new treatment. I am talking about cancer, the illness I am most familiar with.