Edward Banfield draws a distinction between the poor and the lower-class. The poor lack wealth. The lower-class lack patience — they seek instant gratification. This explains mortality rates in the 19th century:
Probably the lower-class poor died from want more often than did the other poor; certainly they died more often from syphilis, excessive drinking, accidents, and homicide. It is probably indicative of differences in class culture that, at the turn of the century, the life expectancy at age ten of the Irish immigrant was only thirty-eight years, whereas for the Russian Jew (who did not brawl or drink and whose religious observances probably had some hygienic value), it was a little more than fifty.
(From The Unheavenly City Revisited).