In the United States, Medicare starts at age 65. So to the extent health care improves health outcomes, we should see a noticeable uptick in results as people reach 65, at least relative to the trajectory of aging they otherwise would experience. Of course many other national health care systems treat 64 and 65-year olds as the same, so we can compare the American case to those alternatives. That would give us a better sense of the relative performance of single-payer coverage, no?
Has such a study been done, and if so what did it yield?