Nurse Practitioners and Physician Assistants in the United States: Current Patterns of Distribution and Recent Trends. Preliminary Tables and Figures

Transcription

1 Nurse Practitioners and Physician Assistants in the United States: Current Patterns of Distribution and Recent Trends Preliminary Tables and Figures Kevin M. Stange, PhD Assistant Professor Gerald R. Ford School of Public Policy University of Michigan Deborah A. Sampson, PhD, FNP BC, APRN Assistant Professor Connell School of Nursing Boston College September

2 I. Introduction, Data Sources, and Methods This paper presents tables and charts of preliminary descriptive findings from a long term research project analyzing changes in the primary care workforce. The project places a particular emphasis on the growth of nurse practitioners (NPs) and physician assistants (PAs) over the past two decades. All analysis is conducted using county level data on workforce supply and many county characteristics obtained from a number of different sources. Since existing data sources do not have consistent data on the number of non physician clinicians (especially nurse practitioners) at the sub state level, we have constructed measures of the number of NPs and PAs over time by county using licensing records obtained from individual state Boards of Nursing, Medicine, Health, Commerce and other relevant state licensing agencies. In most states, health care provider license information is public record and can be purchased, requested via a Freedom of Information Act, or otherwise obtained by request or download. The typical license record includes the provider s name, mailing address (typically home), license number, license type, issue date, expiration date, and status. We have used these individual records to construct counts of the number of active NP and PA licenses in each county of residence in each year. Where possible, this individual license data was supplemented with county level summaries of licensed providers published by state license boards, typically in their annual reports. Since most NPs and PAs are not required to report a specialty, we currently assume all are potentially engaged in primary care. In addition, licenses with out of state addresses are excluded from county and state totals. Table 1 summarizes the coverage of our data. We successfully constructed or obtained data on current licensed providers by county for all but four states (including DC), representing 93% of the U.S. population and 95% of all U.S. counties. For more than half of these, we were able to obtain some historical data for both NPs and PAs. Data on the number of primary care physicians by county for was obtained from the Area Resource File, published by the Health Services Resource Administration. Since this physician data is currently only available through 2007, estimates for 2008 and 2009 were constructed using a linear extrapolation of the county specific estimated trend from 2004 through Throughout primary care physicians refers to non Federal MDs working in patient care in the specialties of general medicine, general family practice, general internal medicine, general pediatrics, and general ob/gyn. Population by county was obtained from the U.S. Census. All other county characteristics were extracted from the Area Resource File. 2

3 Table 1. Overview of County level NP and PA License Data Coverage, by State No. of Population Nurse practitioners Physician assistants No. of Population Nurse practitioners Physician assistants counties (1,000s) Source Earliest Source Earliest counties (1,000s) Source Earliest Source Earliest AK I 2009 I 2009 MT I 2009 I 1990 AL 67 4,709 I 2009 I 1998 NC 100 9,381 A 1990 A 1990 AR 75 2,889 A,I 1999 I 2009 ND I 1990 I 2009 AZ 15 6,596 I 1990 I 1990 NE 93 1,797 I 1990 I 1990 CA 58 36,962 I 1990 I 1990 NH 10 1,325 I 2007 I 1998 CO 64 5,025 I 1995 I 1990 NM 33 2,010 A,I 1995 A,I 1990 CT 8 3,518 I 1991 I 1993 NV 17 2,643 I 1990 A 1992 DE I 1992 I 1992 NY 62 19,541 A 1995 A 1995 FL 67 18,538 I 1990 I 1990 OK 77 3,687 A,I 2005 I 1990 GA 159 9,829 I 1997 I 1990 OR 36 3,826 A,I 2000 I 2009 HI 5 1,295 I 1998 I 1990 PA 67 12,605 I 1990 I 1990 IA 99 3,008 A 1999 I 1990 RI 5 1,053 I 1992 I 1990 ID 44 1,546 A 2007 I 2009 SC 46 4,561 I 1990 I 1990 IL ,910 I 2001 I 1990 SD A,I 2005 I 2009 IN 92 6,423 I 2009 I 2009 TN 95 6,296 I 2004 I 1990 KS 105 2,819 I 1990 I 1990 TX ,782 A 1990 A 1991 KY 120 4,314 I 1990 I 2009 UT 29 2,785 I 1990 I 1990 LA 64 4,492 A 2002 I 1990 VA 135 7,883 I 1990 I 1990 MA 14 6,594 I 1990 I 1990 VT I 1990 I 1990 MD 24 5,699 I 2009 I 1990 WA 39 6,664 I 1990 I 1990 ME 16 1,318 I 1990 I 1990 WI 72 5,655 I 1996 I 1990 MI 83 9,970 I 2000 I 1990 WV 55 1,820 A 2008 A 1996 MN 87 5,266 I 1999 I 1990 Total ,598 MO 115 5,988 I 2009 I 2009 % US 96% 93% MS 82 2,952 A,I 2009 A,I 2009 Notes: Data source indicated by "I" signifies individual license records aggregated up to county of residence while "A" signifies that number of licensed professionals obtained from published tabulations (typically annual reports). Data has not yet been obtained from DC, NJ, OH, or WY. 3

4 II. Current Distribution of Nurse Practitioners and Physician Assistants in the United States This section presents descriptive evidence on the geographic distribution and concentration of NPs and PAs for Throughout we use two measures of NP and PA supply: the share of primary care providers that are NPs or PAs and the NP or PA to physician ratio. These measures offer alternate ways of normalizing for differences in number of providers across areas, in order to focus on differences in provider mix. Table 2A presents the NP and PA share by state at three points in time. In 2009, NPs accounted for 27% of primary care providers nationally, though there is considerable variation across states. The physician assistant share is approximately half this, at 15%. Table 2B presents a similar analysis of NPs and PAs per primary care MD. Nationally, there are 0.48 NPs and 0.28 PAs per primary care MD. Figures 1 through 4 plot the provider to physician ratio and the provider type share by county for Though the cross state variation is apparent, much of the variation actually occurs within state. Statelevel analysis will necessarily miss the large differences in workforce mix between counties in the same state. Table 3 highlights some differences between counties with high and low reliance on NPs and PAs. NPs tend to be a greater share of the primary care workforce in less dense, less urban, lower income areas with fewer minorities. They also tend to have a greater share in areas with fewer providers per population and that are designated as health provider shortage areas. HMO penetration is actually negatively correlated with NP share. The pattern for PAs is directionally similar, though less pronounced, as PAs tend to locate near physicians more than NPs. Results are virtually identical regardless of whether counties are categorized according to provider to physician ratios and provider type shares. In Figure 5, counties are categorized according to the type of provider that constitutes a majority of primary care providers, if any. Though most counties are still served primarily by physicians, there are many areas for which NPs or PAs are more than half of the workforce or for which no single provider type dominates. 4

5 Table 2A. Nurse Practitioner and Physician Assistant Share of Primary Care Workforce, by State NP Share of Primary Care PA Share of Primary Care NP Share of Primary Care PA Share of Primary Care AK MT AL NC AR ND AZ NE CA NH CO NM CT NV DE NY FL OK GA OR HI PA IA RI ID SC IL SD IN TN KS TX KY UT LA VA MA VT MD WA ME WI MI WV MN Total MO MS Notes: NP share is defined as the ratio between number of licensed nurse practitioners and the total of primary care MDs, physician assistants, and nurse practitioners in a given area. PA share is defined similarly. Total is calculated as the population weighted average for states with data in a particular year, so the sample composition changes over time. The aggregate trend is nearly identical when a balanced panel of 22 states is used instead 5

6 Table 2B. Nurse Practitioner and Physician Assistants per Primary Care MD, by State NPs per Primary Care MD PAs per Primary Care MD NPs per Primary Care MD PAs per Primary Care MD AK MT AL NC AR ND AZ NE CA NH CO NM CT NV DE NY FL OK GA OR HI PA IA RI ID SC IL SD IN TN KS TX KY UT LA VA MA VT MD WA ME WI MI WV MN Total MO MS Notes: Primary care includes familly and general practice MDs, Ob/Gyn MDs, general pediatricians, and general internal medicine MDs. Total is calculated as the population weighted average for states with data in a particular year, so the sample composition changes over time. The aggregate trend is nearly identical when a balanced panel of 22 states is used instead 6

7 Figure 1: Map of Number of Nurse Practitioners per Primary Care MD by county, 2009 Number of NPs per Primary Care MD, 2009 US Average: or more No primary care MDs in county Data unavailable Figure 2: Map of Number of Physician Assistants per Primary Care MD by county, 2009 Number of PAs per Primary Care MD, 2009 US Average: or more No primary care MDs in county Data unavailable 7

8 Figure 3: Map of Nurse Practioner Share of Primary Care Workforce by County, 2009 NPs as a Share of all Primary Care Providers, 2009 US Average: 27% % 30-49% 20-29% 10-19% 0-9% No primary care providers in county Data unavailable Figure 4: Map of Physician Assistant Share of Primary Care Workforce by County, 2009 PAs as a Share of all Primary Care Providers, 2009 US Average: 15% % 30-49% 20-29% 10-19% 0-9% No primary care providers in county Data unavailable 8

9 Table 3A. Differences in County Characteristics between High and Low NP/PA Share Areas NP Share of Primary Care, 2009 PAs Share of Primary Care, 2009 Low High Difference t-stat Low High Difference t-stat Population density (1995) 2, , ,189 1, % Urban (1989) Per capita income (1990) ($1000) % College or greater (1990) % Hispanic (1990) % Black (1990) Health Provider Shortage Area (2000) MDs per 100,000 pop, (1995) HMO penetration (1998) Notes: Each panel divides the sample into two equally-sized groups: high (above median) NP or PA share in 2009 and low (below median) NP or PA share in Primary care includes all NPs, PAs, family and general practice MDs, Ob/Gyn MDs, general pediatricians, and general internal medicine MDs. Test statistic is for the null hypothesis that the two groups have the same population mean, with an absolute value greater than 1.96 rejecting the null. Each county is weighted by population, though results are directionally and statistically similar with unweighted samples. The sample includes 2945 counties due to missing physician data or lack of any providers for a small number of counties. 9

10 Table 3B. Differences in County Characteristics between High and Low NP/PA -to-physician Areas NPs per Primary Care MD, 2009 PAs per Primary Care MD, 2009 Low High Difference t-stat Low High Difference t-stat Population density (1995) 2, , ,175 1, % Urban (1989) Per capita income (1990) ($1000) % College or greater (1990) % Hispanic (1990) % Black (1990) Health Provider Shortage Area (2000) MDs per 100,000 pop, (1995) HMO penetration (1998) Notes: Each panel divides the sample into two equally-sized groups: high (above median) NP or PA per primary care MD in 2009 and low (below median) NP or PA primary care MD in Primary care includes familly and general practice MDs, Ob/Gyn MDs, general pediatricians, and general internal medicine MDs. Test statistic is for the null hypothesis that the two groups have the same population mean, with an absolute value greater than 1.96 rejecting the null. Each county is weighted by population, though results are directionally and statistically similar with unweighted samples. The sample includes 2739 counties due to missing physician data or no physicians for a small number of counties. 10

11 Figure 5: Map of counties with majority of primary care workforce a single type, 2009 Counties with majority of primary care providers a single type, 2009 Majority NPs Majority PAs No majority Majority MDs No primary care providers in county Data not available 11

12 III. Recent Trends in the Concentration of Nurse Practitioners and Physician Assistants Table 2A shows the NP and PA share by state for 1995, 2000, and Across all states, the NP share grew from 17% to 27% from 1995 to 2009 and the PA share grew from 9% to 15% over the same period. The same pattern is observed in Table 2B, which contains the number of NP and PAs per primary care MD in these same years. Across all states, the number of NPs per primary care MD grew from 0.23 to 0.48 and the number of PAs per primary care MD grew from 0.12 to All states for which data is available witnessed a growth of PA and NP penetration. Table 4 shows how the fraction of counties and population that are served by a majority of providers of a single type has changed over time. Again, each county is categorized according to the type of provider (if any) that constitutes a majority of primary care providers in each year. The data in Panel A is not weighted, so the trend reflects the fraction of counties in each category irrespective of the population. The fraction of counties that are not served primarily by a single type of provider has grown considerably over the past decade. In Panel B the observations are weighted according to population, so the trend reflects the fraction of the population living in each type of county. Approximately one fifth of the U.S. population lives in a county without a majority provider type, a three fold increase over the past decade. Figure 6 shows these trends graphically, plotting counties by provider category for 2000 and 2009.The growth of non majority counties is very apparent, both across and within states. 12

13 Table 4: Share of Counties and Population Served by a Majority of Providers of a Single Type, Longitudinal Panel of Counties All Panel A: Fraction of Counties Majority NPs Majority PAs No Majority Majority MDs No providers Total Panel B: Fraction of the Population Majority NPs Majority PAs No Majority Majority MDs No providers Total Panel A depicts the fraction of US counties that is served by a majority of providers of a single type. All counties are given equal weight in this calculation. Panel B depicts the fraction of the US population that lives in counties served by a majority of providers of a single type. The longitudinal panel includes the 1741 counties in 27 states for which data was available for the full panel. The final column includes all counties excluding those in DC, NJ, OH, and WY. 13

14 Figure 6: Map of Counties with Majority of Primary Care Workforce a Single Type, 2000 to 2009 Counties with majority of primary care providers a single type, 2000 (Only counties with data for 2000 and 2009) Majority NPs Majority PAs No majority Majority MDs No primary care providers in county Counties with majority of primary care providers a single type, 2009 (Only counties with data for 2000 and 2009) Majority NPs Majority PAs No majority Majority MDs No primary care providers in county Data not available 14