Medicaid coverage had no detectable effect on the prevalence of diabetes, high cholesterol or hypertension among low-income adults in a study, but substantially reduced depression, nearly eliminated catastrophic out-of-pocket expenditures and increased the diagnosis of diabetes and the use of diabetes medication.
Data came from the Oregon Health Insurance Experiment, described as the first use of a randomized controlled study design to evaluate the impact of covering the uninsured with Medicaid. Researchers said the study, published in the May 2 issue of the New England Journal of Medicine, provides important evidence for policymakers as the U.S. undertakes Medicaid expansion in 2014.
“This study represents a rare opportunity to evaluate the costs and benefits of expanding public insurance using the gold standard of scientific evidence — the randomized controlled trial,” Katherine Baicker, PhD, a lead investigator in the study and professor of health economics at the Harvard School of Public Health, said in a news release. “Without a randomized evaluation, its difficult to disentangle the effects of Medicaid from confounding factors like income and health needs that also affect outcomes.”
In 2008, Oregon held a lottery to give additional low-income, uninsured residents access to its Medicaid program. About 90,000 individuals signed up, hoping to get chosen for one of 10,000 available openings. Approximately two years after the lottery, the researchers conducted more than 12,000 in-person interviews and health examinations of lottery participants in the Portland metropolitan area, and compared outcomes between those randomly selected in the lottery and those not selected.
Physical health: Medicaid had no significant effect on measures of hypertension or high cholesterol, or on the rates of diagnosis or use of medication for these conditions.
Medicaid increased the probability of being diagnosed with diabetes after the lottery by 3.8 percentage points (compared with the 1.1% of the control group who were diagnosed with diabetes) and increased the use of diabetes medication by 5.4 percentage points (compared with 6.4% of the control group), but had no effect on glycated hemoglobin.
Mental health: Medicaid reduced rates of depression by 9 percentage points (compared with the 30% of the control group screening positive for depression) and increased self-reported mental health.
Financial hardship: Medicaid virtually eliminated out-of-pocket catastrophic medical expenditures (defined as out-of-pocket medical expenditures in excess of 30% of household income) and reduced other measures of financial strain.
Utilization and access: Medicaid increased healthcare use, including use of physician services, prescription drugs and preventive care.
“The study highlights the important financial protections that Medicaid provides, as well as the substantial improvements in mental health, but does not provide evidence that Medicaid coverage translates to measurable improvements in physical health in the first two years,” said Amy Finkelstein, PhD, a co-lead investigator of the study and Ford professor of economics at the Massachusetts Institute of Technology.
A previous study looking at data collected about a year after the lottery found that Medicaid substantially increased healthcare use, increased self-reported health, and reduced financial strain.
Read the study abstract: www.nejm.org/doi/full/10.1056/NEJMsa1212321.
Get more information on the Oregon Health Insurance Experiment: www.nber.org/oregon.