It might also not only be age. Sailors on the Roosevelt are likely to be less obese than average, more fit, maybe lower rates of smokers (not sure) and certainl

It might also not only be age. Sailors on the Roosevelt are likely to be less obese than average, more fit, maybe lower rates of smokers (not sure) and certainly lower rates of other pre-existing conditions. That all puts them in lower risk groups. Just the higher share of men increases risk somewhat. But overall they certainly don't represent the average US population.