A growing and aging population, along with increased access to health insurance, will create the need for 52,000 more primary care doctors within the U.S. by the year 2025, according to a new study.

The researchers wanted to estimate how many such doctors the U.S. healthcare system would need after the passage of 2010’s Affordable Care Act, which will give an estimated 34 million more Americans access to health insurance.

But Dr. Winston Liaw, one of the study’s authors, said the biggest need will not come from more people having health insurance.

“A lot of the increase in utilization is going to be from population growth. That’s going to be the largest driver. Then, a smaller percentage is actually going to be from insurance expansion,” said Liaw, who was a fellow at Washington’s Robert Graham Center when the study was written.

Liaw and his colleagues, who published their findings in the Annals of Family Medicine, used several databases to estimate how many primary care doctors there are in the U.S., and how many people visit them.

They then used that information with additional data from the U.S. Census Bureau to predict how many doctors would be needed as the population grew, aged and gained access to health insurance.

In 2008, the researchers estimated that people made 462 million office visits to primary care doctors. They estimate that number to grow to 565 million office visits by 2025.

That additional use, they say, will require a 3 percent increase in the current primary doctor workforce, or an additional 52,000 doctors.

“That number is an expectation of how many we’ll need in addition to how many we have today,” said Liaw, now at Virginia Commonwealth University in Fairfax.

Of those, 33,000 doctors are needed to account for population growth, 10,000 for the aging population and more than 8,000 for increased insurance access.

“The fact that they made separate estimates for the increased demands for primary care services that might be due to population growth on the one hand, and aging of the population and thirdly the Affordable Care Act is a very useful addition to this area,” said Dr. John Rowe of the Columbia University Mailman School of Public Health in New York.