I'm not sure they determined that it did not improve lifespans. Here's some snippets from the Wikipedia article (
https://en.wikipedia.org/wiki/Oregon_Medicaid_health_experim...):
> On average, Medicaid coverage increased annual medical spending by approximately $1,172 relative to spending in the control group. The researchers looked at mortality rates, but they could not reach any conclusions because of the extremely low death rate of the general population of able-bodied Oregon adults aged 19 to 64.
> In the first year after the lottery, Medicaid coverage was associated with higher rates of health care use, a lower probability of having medical debts sent to a collection agency, and higher self-reported mental and physical health. In the 18 months following the lottery, researchers found that Medicaid increased emergency department visits.
> Approximately two years after the lottery, researchers found that Medicaid had no statistically significant impact on physical health measures, but "it did increase use of health care services, raise rates of diabetes detection and management, lower rates of depression, and reduce financial strain."