In an effort to respond to what one hospital executive termed a “primary care crisis,” two Harvard-affiliated teaching hospitals will shift their pay structure so that doctors are paid in part based on the number of patients they treat and the complexity of those patients’ conditions.

About ten percent of doctors’ salaries at Brigham and Women’s Hospital and Massachusetts General Hospital will be allocated based on the size of their practices, rather than the two percent based on practice size at MGH last year.

The new pay policy springs from an increasing demand for primary care, according to Joseph P. Frolkis, vice chair of primary care at Brigham and Women’s Hospital.

Frolkis said in an email that as baby boomers age, the population has become older and sicker, requiring more time and attention from doctors.

In addition, he said that the roughly 32 million new patients who have acquired health insurance under the Patient Protection and Affordable Care Act of 2010 have put further strain on hospitals.

Now, Frolkis said, there is a growing gap as demand for doctors’ services outpaces the number of primary care practitioners.

The new compensation model is meant to plug that gap by spurring doctors to take on new patients.

Eric M. Weil, associate medical director for primary care at MGH, said that the new payment scheme should also better reflect physicians’ work.

“Much of primary care is conducted outside of face-to-face interaction with the patient and is spent on coordination for health coverage,” Weil said. “This was not reflected in the previous compensation model.”

Frolkis said that the former system led some doctors to stop taking new patients entirely.

“In a traditional primary care setting, physicians can feel out-of-control,” he wrote. “In this context, they can be de-motivated to take on new patients—who may take more time and can be labor intensive, especially given the number of elderly individuals seeking care.”

The compensation change, Folkis added, “allows physicians to feel that they can take on new patients, and give them the attention they deserve.”

Weil, who helped create the new model at MGH, noted that now, “having more complicated patients should mean the doctor gets more compensation.”

But Weil acknowledged that calculating the complexity of primary care in order to determine doctors’ salaries may prove challenging.

“It’s too early to tell what effect this will have, but we’re optimistic,” Weil said.

—Staff writer Armaghan N. Behlum can be reached at behlum@college.harvard.edu.