Market influences on internal medicine residents' decisions to subspecialize

Background: Managed care reduces the demand for internal medicine subspecialists, but little empirical information is available on how increasing managed care may be affecting residents' training choices. Objective: To determine whether increased managed care penetration into an area where residents train was associated with a decreased likelihood that residents who completed general internal medicine training pursued subspecialty training. Design: Secondary logistic regression analysis of data from the 1993 cohort of general internal medicine residents. Setting: U.S. residency training sites. Participants: 2263 U.S. medical school graduates who completed general internal medicine residency training in 1993. Measurements: The outcome variable (enrollment in subspecialty training) was derived from the Graduate Medical Education Tracking Census of the Association of American Medical Colleges (AAMC). Health maintenance organization (HMO) penetration (possible range, 0.0 to 1.0; higher values indicate greater penetration) was taken from the Interstudy Competitive Edge Database. Individual and medical school covariates were taken from the AAMC's Student and Applicant Information Management System database and the National Institutes of Health Information for Management Planning, Analysis, and Coordination system. The U.S. Census division was included as a control covariate. Results: 980 participants (43%) enrolled in subspecialty training. Logistic regression analyses indicated a nonlinear association between managed care penetration into a training area and the odds of subspecialization. Increasing managed care penetration was associated with decreasing odds of subspecialization when penetration exceeded 0.15. The choice of subspecialty training increased as HMO penetration increased from 0 to 0.15. Conclusions: Local market forces locally influenced the career decisions of internal medicine residents, but the influence was small compared with the effects of age and sex. These results suggest that market forces help to achieve more desirable genera list-to-specialist physician ratios in internal medicine.