I think it continues in a person because of the surrounding environment they are in. Our health is the most important priority and dictates whether we live or die essentially which then causes more anxiety in a person. The importance of health in a person can cause continuous anxiety because it is always going to be a large part of our lives. Their obsession perpetuates from constant reminders that their health dictates their pain and ultimate survival.
Hope this helped! This is merely an opinion :)