To my mind probably the single most solid piece of evidence is this: turning 65–i.e., going on Medicare–doesn't reduce your risk of dying. If lack of insurance leads to death, then that should show up as a discontinuity in the mortality rate around the age of 65. It doesn't. There are some caveats–if the effects are sufficiently long term, then it's hard to measure, because of course as elderly people age, their mortality rate starts rising dramatically. But still, there should be some kink in the curve, and in the best data we have, it just isn't there.
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.
I agree with her conclusion:
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.