Washington - An estimated 10.3 million American adults have gained health coverage since Obamacare enrolment began last October, with the biggest gains among young adults and Hispanics, according to a study published on Wednesday.
The findings by researchers from the Harvard School of Public Health, Brigham and Women's Hospital in Boston and the federal government are based on data pointing to a 5.2 percentage point drop in the US uninsured rate since last September for Americans aged 18 to 64.
The study, which appeared in the New England Journal of Medicine, also found evidence that more Americans had a personal doctor and fewer difficulties paying for medical care within the first six months of gaining insurance.
The law known as Obamacare, President Barack Obama's signature domestic policy achievement, provides federally subsidised private coverage through new online insurance marketplaces and an expansion of Medicaid in 26 states and Washington, DC
The US Department of Health and Human Services said in May that more than 8 million Americans signed up for private plans through new online insurance marketplaces during a six-month open enrolment period.
Official data show another 7 million people gaining coverage under Medicaid, but the data includes renewals in existing Medicaid programs as well as new enrolments.
Wednesday's study, published in the New England Journal of Medicine, compared national survey results with Census data as well as government figures on marketplace enrolment in private insurance and Medicaid.
The authors said their data was not complete enough to show a causal relationship between Obama's Affordable Care Act and the uninsured rate. Instead, they said the findings identified "suggestive associations."
The data did not include an estimated 3 million young adults estimated to have gained coverage by joining their parents' insurance policies under Obamacare.