and of course, those who on a cruise ship are generally middle-class if not wealthy no-need-to-work people, so projecting that population onto the american population will tend to error, as wealthier people tend to have better medical care and thus less "pre-existing" conditions. On the other hand, for people suffering from chronical or critical disease, it wouldn't make sense for them to take on a cruise trip, where they won't have access to sufficient medical services. Yet, that's quite possible for many of us. Thus the population on the cruise is already healthier than the general population of the same age.