The data sometimes work in mysterious ways and provide puzzling correlations that lead to interesting research questions. One such correlation is that exemption from military service leads to lower mortality later in life.
Piero Cipollone and Alfonso Rosolia find this while looking at a natural experiment following the 1981 earthquake in Southern Italy. Boys from the affected region were exempted from military service, and they were followed, along with non-exempted neighbors, to track their life and education. By concentrating on boys both sides close to the border of the exempt region, they find that those exempt ended up being more educated. I can easily believe that, as they were not spending some of their prime learning years hiding in bushes and peeling potatoes, and they were expecting a longer work life. But the exempt also have lower mortality. This is not due to a lower incidence of military accidents, it is rather linked to the higher school completion rates. In fact, the authors conclude that raising high school completion by 10 percentage points would lower mortality by one or two percentage points in the decade thereafter. That is impressive at that age.