As early as the 1970s, researchers found that immigrants lived several years longer than American-born whites even though they tended to have less education and lower income, factors usually associated with worse health. That gap has grown since 1980…Evidence is mounting that the second generation does worse. Exploratory estimates based on data from 2007 to 2009…show that Hispanic immigrants live 2.9 years longer than American-born Hispanics.
[One study] found that immigrants had at least a 20 percent lower overall cancer mortality rate than their American-born counterparts.
Mortality rates from heart disease were about 16 percent lower, for kidney disease 18 percent lower, and for liver cirrhosis 24 percent lower.
This is from The NYT.