NCHS Data Brief ■ No. 69 ■ August 2011

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

Nurse Practitioners, Certified Nurse Midwives, and 

Physician Assistants in Physician Offices

Melissa Park, M.P.H.; Donald Cherry, M.S.; and Sandra L. Decker, Ph.D. 

Key findings

Data from the National 

Ambulatory Medical Care 

Survey, 2009

• In 2009, 49.1% of officebased physicians were in 

practices that used nurse 

practitioners (NPs), certified 

nurse midwives (CNMs), or 

physician assistants (PAs). 

• Primary care physicians 

were more likely to have NPs, 

CNMs, or PAs than physicians 

of other specialities.

• Physicians in larger and 

multi-specialty group practices 

were more likely to work with 

NPs, CNMs, or PAs than those 

in smaller and single-specialty 

group practices. 

• Older physicians were 

less likely than middle-aged 

physicians to be in practices 

that had NPs, CNMs, or PAs. 

• Physicians in practices with 

a higher proportion of revenue 

from Medicaid and a lower 

proportion from Medicare were 

more likely to work with NPs, 

CNMs, or PAs.

The expansion of health insurance coverage through health care reform, 

along with the aging of the population, are expected to strain the capacity for 

providing health care (1–3). Projections of the future physician workforce 

(4,5) predict declines in the supply of physicians and decreasing physician 

work hours (6,7) for primary care (8–10). An expansion of care delivered by 

nurse practitioners (NPs), certified nurse midwives (CNMs), and physician 

assistants (PAs) is often cited as a solution to the predicted surge in demand 

for health care services and calls for an examination of current reliance on 

these providers (11,12). Using a nationally based physician survey, we have 

described the employment of NPs, CNMs, and PAs among office-based 

physicians by selected physician and practice characteristics. 

Keywords: National Ambulatory Medical Care Survey • office-based 

physicians • practice characteristics

Primary care physicians were more likely to work with NPs, 

CNMs, or PAs than physicians in other specialties. 

• Overall, 49.1% of physicians in 2009 were in practices that had NPs, 

CNMs, or PAs (Figure 1). 

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NCHS Data Brief ■ No. 69 ■ August 2011

■  2  ■

• In 2009, a higher percentage of primary care physicians (55.4%) had NPs, CNMs, or PAs 

associated with their practice than did surgical specialists (45.9%) and medical specialists 

(40.8%). 

NPs, CNMs, or PAs were most likely to be associated with physicians who 

worked in large group practices.

• Among all three specialty categories, physicians in larger practices were more likely to have 

NPs, CNMs, or PAs compared with those in smaller practices. 

• Among primary care specialists, for example, 37.6% of physicians in practices with at most 

one other physician worked with NPs, CNMs, or PAs compared with 65.0% of those in 

practices with 3–10 physicians and 79.9% of those with at least 11 total physicians. 

• Physicians in surgical and medical specialties followed this same pattern, with those in 

larger practices being more likely to have NPs, CNMs, or PAs (Figure 2).

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NCHS Data Brief ■ No. 69 ■ August 2011

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Physicians in multi-specialty group practices were most likely to work with 

NPs, CNMs, or PAs. 

• Figure 3 shows that physicians in multi-specialty group practices were most likely to have 

NPs, CNMs, or PAs (68.3%) compared with those in single-specialty group practices 

(53.8%) and solo practices (31.1%). 

• Comparing types of group practices, multi-specialty practices were more likely to have NPs, 

CNMs, or PAs (68.3%) compared with single-specialty practices (53.8%).

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NCHS Data Brief ■ No. 69 ■ August 2011

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Older office-based physicians were less likely to work with NPs, CNMs, or 

PAs. 

• Older physicians were less likely than middle-aged physicians to work with NPs, CNMs, or 

PAs (Figure 4). 

• In 2009, 43.5% of physicians aged 55 and over were in practices with at least one NP, CNM, 

or PA compared with 54.1% of physicians aged 45–54.

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NCHS Data Brief ■ No. 69 ■ August 2011

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Physicians in practices with more revenue from Medicaid and less revenue 

from Medicare were more likely than others to work with NPs, CNMs, or 

PAs.

• Physicians in practices with more revenue from Medicare were less likely (45.4%) than 

those in practices with less revenue from Medicare (52.3%) to work with NPs, CNMs, or 

PAs (Figure 5). 

• Conversely, physicians in practices with more revenue from Medicaid were more likely than 

those with less revenue from Medicaid to work with NPs, CNMs, or PAs (53% compared 

with 45.2%). 

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Summary

The expansion of health insurance coverage, as well as the aging baby-boomer population, are 

predicted to cause a surge in demand for health care services in the coming years. Examining the 

current employment of NPs, CNMs, and PAs in physician offices is important in order to prepare 

for the future. In 2009, 49% of physicians were in practices that worked with NPs, CNMs, or PAs. 

Physicians in primary care were more likely to work with NPs, CNMs, or PAs than physicians 

in other specialties. Physicians in large and multi-specialty group practices, compared with 

solo and single-specialty practices, were more likely to work with NPs, CNMs, or PAs. Older 

physicians were less likely than younger physicians to be in practices that had NPs, CNMs, or 

PAs. Physicians in practices with less revenue from Medicare and those with more revenue from 

Medicaid were more likely to work with NPs, CNMs, or PAs. 
NCHS Data Brief ■ No. 69 ■ August 2011

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The role of NPs, CNMs, or PAs in the provision of health care is likely to increase in future years 

(12). The Patient Protection and Affordable Care Act legislation, signed into law on March 23, 

2010, contains several provisions affecting the likely future supply of NPs, CNMs, and PAs (13). 

Specifically, these provisions include a 15% carve-out for PA educational programs in the funding 

for primary care medicine, making PA educational programs eligible for faculty loan repayment 

grants and grants for authorized nurse-midwifery education programs. Such incentives are likely 

to increase the supply of certain NPs, CNMs, and PAs. Increasing the supply of these practitioners 

may, in turn, affect the types of practices that use NPs, CNMs, or PAs. 

Definitions

Percent revenue by source: Percentages of individual payment sources (i.e., Medicare, Medicaid, 

private insurance, or patient payments) that contribute to a physician’s overall practice revenue 

from patient care. 

Physicians working with at least one nurse practitioner (NP), certified nurse midwife (CNM), or 

physician assistant (PA): The following question on the 2009 National Ambulatory Medical Care 

Survey (NAMCS) induction form was used to assess whether a physician had affiliated NPs, 

CNMs, or PAs at the location at which the physician saw the most patients: “How many mid-level 

providers (i.e., nurse practitioners, physician assistants, and nurse midwives) are associated with 

you at this in-scope location?” 

Specialty type: NAMCS samples physicians in 14 American Medical Association (AMA)

specialties and a miscellaneous specialty category. These specialties are grouped into three 

major categories: primary care, surgical, and medical, as shown in Figures 1 and 2. Major 

specialties included in the primary care grouping are internal medicine, family practice or general 

practice, pediatrics, and obstetrics and gynecology. Major specialties in the surgical category 

include general surgery, orthopedic surgery, urology, ophthalmology, and otolaryngology. Major 

specialties in the medical category are cardiovascular diseases, dermatology, psychiatry, and 

neurology. However, for analytic purposes, some subspecialties of pediatrics and obstetrics and 

gynecology are reclassified as medical or surgical. Less common specialties are also divided into 

these three groupings. For a complete description of all specialties and subspecialties included in 

the specialty type groupings, see the 2009 NAMCS Public-use Data File Documentation available 

from: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/NAMCS/doc09.pdf.

Data source and methods

Data from 2009 NAMCS were used for these analyses. NAMCS is a national probability sample 

survey of nonfederal, office-based physicians in the United States conducted by the Centers for 

Disease Control and Prevention’s (CDC) National Center for Health Statistics (NCHS), Division 

of Health Care Statistics. The target universe of NAMCS includes visits made in the United 

States to the offices of nonfederally employed physicians—excluding those in the specialties 

of anesthesiology, radiology, and pathology—who were classified by AMA and the American 

Osteopathic Association as providing “office-based, patient care.” 

NAMCS utilizes a multistage probability sample design involving samples of geographic primary 

sampling units (PSUs), physician practices within PSUs, and patient visits within physician 

practices. PSUs are counties, groups of counties, county equivalents, or for some PSUs in New 
NCHS Data Brief ■ No. 69 ■ August 2011

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England, towns and townships. A sample weight is computed for each sample visit that takes 

all stages of design into account. The survey data are inflated or weighted to produce unbiased 

national annual estimates of physician office visits and unbiased annual estimates of physician 

characteristics, including attributes of their practices. Only physician-level statistics were utilized 

in this brief. Analysis was based on the sample of 1,592 physicians, after dropping 35 physicians 

missing information on employment of NPs, CNMs, or PAs. 

The sampling approach for NAMCS excludes the collection of information about NPs, CNMs, 

and PAs with independent practices. In addition, information collected about visits to physicians 

in NAMCS does not routinely include information about visits to NPs, CNMs, or PAs except 

those in community health centers. Long-term trend analysis on the employment of NPs, CNMs, 

and PAs in physician offices is not possible with NAMCS because this information was not 

collected for all physicians until 2007. 

Differences in the employment of NPs, CNMs, or PAs by physician practice characteristics were 

evaluated with two-tailed t tests using p < 0.05 as the level of significance. No corrections were 

made for multiple comparisons. All comparisons reported in the text are statistically significant. 

Data analyses were performed using the statistical packages SAS version 9.2 (SAS Institute, 

Cary, N.C.), SUDAAN version 10.0 (RTI International, Research Triangle Park, N.C.), and 

STATA version 11.0 (College Station, Texas).

About the authors

Melissa Park, Donald Cherry, and Sandra L. Decker are with the Centers for Disease Control and 

Prevention’s National Center for Health Statistics, Division of Health Care Statistics. 

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Suggested citation

Park M, Cherry D, Decker SL. Nurse 

practitioners, certified nurse midwives, and 

physician assistants in physician offices. 

NCHS data brief, no 69. Hyattsville, MD: 

National Center for Health Statistics. 2011.

Copyright information

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the public domain and may be reproduced 

or copied without permission; citation as to 

source, however, is appreciated.

National Center for Health 

Statistics

Edward J. Sondik, Ph.D., Director

Jennifer H. Madans, Ph.D., Associate 

Director for Science

Division of Health Care Statistics

Jane E. Sisk, Ph.D., Director

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