STATE PRACTICE ENVIRONMENTS AND THE SUPPLY OF PHYSICIAN ASSISTANTS, NURSE PRACTITIONERS, AND CERTIFIED NURSE-MIDWIVES

Background. Most proposals to increase access to primary care in the U nited States emphasize increasing the proportion of generalist physici ans. Another approach is to increase the number of physician assistant s, nurse practitioners, and certified nurse-midwives. Methods. We anal yzed variations in the regulation of nurse practitioners, physician as sistants, and certified nurse-midwives in all 50 states and the Distri ct of Columbia. Using a 100-point scoring system, we assigned numerica l values to specific characteristics of the practice environment in ea ch state for each group of practitioners, awarding a maximum of 20 poi nts for legal status, 40 points for reimbursement for services, and 40 points for the authority to write prescriptions. We calculated coeffi cients for the correlation of summary measures of these values within states with estimates of the supply of practitioners per 100,000 popul ation. Results. There was wide variation among states in both practice -environment scores and practitioner-to-population ratios for all thre e groups of practitioners. We found positive correlations within state s between the supply of physician assistants, nurse practitioners, and certified nurse-midwives and the practice-environment score for the s tate (Spearman rank-correlation coefficients, 0.63 [P < 0.001], 0.41 [ P = 0.003], and 0.51 [P < 0.001], respectively). Positive associations were also found in the stales between the supply of generalist physic ians and the supply of physician assistants (r = 0.54, P < 0.001) and nurse practitioners (r = 0.35, P = 0.014). Nevertheless, in the 17 sta tes with the greatest shortages of primary care physicians, favorable practice-environment scores were still associated with higher practiti oner-to-population ratios for physician assistants (r = 0.68, P = 0.00 3), nurse practitioners (r = 0.54, P = 0.026), and certified nurse-mid wives (r = 0.42, P = 0.09). Conclusions. State regulation of physician assistants, nurse practitioners, and certified nurse-midwives varies widely. Favorable practice environments are strongly associated with a larger supply of these practitioners.