"Viable" is a poignant word to use.
viableIt's a familiar word in the American law relating to abortion.
1828, from Fr. viable "capable of life" (1539), from vie "life" (from L. vita "life;" see vital) + -able. Originally of newborn infants; generalized sense is first recorded 1848.
Is the eldercare problem in Japan really about all the men who died in WWII, or is more about the failure to produce new human beings who might take care of the old?