WASHINGTON - It's the great moral imperative behind the Affordable Care Act ("Obamacare"): People should not be denied health care because they can't afford insurance.
Health status and insurance are assumed to be connected, and opponents have often been cast as moral midgets, willing to condemn the uninsured to unnecessary illness or death.
The trouble is that health status and insurance are only loosely connected. This suggests that Obamacare may result in more spending and health services but few gains in the public's health.
We now have a study based on Medicaid in Oregon implying just that.
Judging the effect of insurance of health effect on health has always been difficult, because the uninsured are different from the insured: They're poorer, younger and often sicker.
How much of their worse health reflects a lack of insurance? To answer, researchers need to compare similar people with and without insurance.
Oregon's expansion of Medicaid - the federal-state insurance for the poor - unwittingly solved this problem. In 2008, the state decided to increase enrollment by 10,000. But there were 90,000 people on the waiting list, so the state adopted a lottery to decide who would receive coverage.
The result was two similar groups of poor, one with insurance (Medicaid) and one without, that could be compared. The New England Journal of Medicine recently published the study.
The most overlooked finding is that the uninsured already receive considerable health care. On average, the uninsured had 5.5 office visits annually, used 1.8 prescription drugs and visited the emergency room once.
Almost half (46 percent) said they "had a usual place of care" and 61 percent said they "received all needed care" in the past year. About three-quarters (78 percent) who received care judged it "of high quality."
Health spending for them averaged $3,257.
True, when people were covered by Medicaid, many of these figures rose.
The number of office visits went to 8.2; the number of drugs, 2.5; the share of patients with a usual place of care, 70 percent; the proportion receiving all needed care, 72 percent.
Preventive care also increased.
The share of patients receiving screening for cholesterol moved from 27 percent for the uninsured to 42 percent; the share of women over 50 having mammograms jumped from 29 percent to 59 percent; the share of men over 50 getting PSA tests for prostate cancer doubled from 21 percent to 41 percent.
Spending rose to $4,429.
Unfortunately, the added care and cost didn't much improve people's physical health.
The study screened for high blood pressure, high cholesterol, diabetes and the risk of a future heart attack or stroke.