That is a great question you ask.
I guess when I pray for other people with a health problem/risk, I ask God to give them strength. I also pray that God watch over them... not necessarily to "heal" them, but to, like I said, give them the strength to help themselves get better. I believe that when a person is healed from their health problems, I believe it is because it is not their "time". Sometimes even if we pray for those sick people, they still pass away or do not get better. I believe God has a time for all of us. God knows when we will die and knows how. I believe God is the one that creates that time. I guess my answer leans more towards the "serious" health risks...