Ultimately, health care seems to be the culprit in Americans' increasingly shorter lifespans. The authors investigated the impact of health insurance on mortality rates, and found that there is very little. They stated that insurance "coverage has large effects on use of health care but only small effects on mortality, which are concentrated in low-income groups."
They go on to note that only a very small difference in life expectancy can be found as a result of access to medical insurance. It should also be pointed out that these studies are looking for such a connection, so their inability to find one should be taken as highly significant.
Modern medicine is the problem. Modern medicine's massive use of poisonous drugs, excessive and unnecessary surgeries, harmful diagnostics, "preventative" treatments, and vaccinations are evoking a dreadful toll on lifespan and quality of life.