But how likely is it that Medicaid is killing people? Possible, I suppose, but not really all that likely. Medicaid and Medicare patients, too, are not like the broader population. The authors in fact recognized this fact in their paper, pointing out that these patients have higher rates of disability--but then failed to address the obvious question this raised about their data on the uninsured.
That doesn't mean I'm prepared to say that no one dies from lack of insurance. The data is messy, and the studies often contradict each other. Intuitively, I feel as if there should be some effect. But if the results are this messy, I would guess that the effect is not very big. At minimum, I think we should be pretty cautious about stating that we know how many people die from lack of insurance. We don't, and worse, we may never."
There are also factors we can't analyze. It's widely believed that health improves with social status, a quality that's hard to measure. Risk-seekers are probably more likely to end up uninsured, and also to end up dying in a car crash—but their predilection for thrills will not end up in our statistics. People who are suspicious of doctors probably don't pursue either generous health insurance or early treatment. Those who score low on measures of conscientiousness often have trouble keeping jobs with good health insurance—or following complicated treatment protocols. And so on.
The studies relied upon by the Institute of Medicine and the Urban Institute tried to control for some of these factors. But Sorlie et al.—the larger study—lacked data on things like smoking habits and could control for only a few factors, while Franks, Clancy, and Gold, which had better controls but a smaller sample, could not, as an observational study, categorically exclude the possibility that lack of insurance has no effect on mortality at all.
The possibility that no one risks death by going without health insurance may be startling, but some research supports it. Richard Kronick of the University of California at San Diego's Department of Family and Preventive Medicine, an adviser to the Clinton administration, recently published the results of what may be the largest and most comprehensive analysis yet done of the effect of insurance on mortality. He used a sample of more than 600,000, and controlled not only for the standard factors, but for how long the subjects went without insurance, whether their disease was particularly amenable to early intervention, and even whether they lived in a mobile home. In test after test, he found no significantly elevated risk of death among the uninsured. "