Why is there variation in the care provided by academic medical centers?
All of these hospitals are academic medical centers affiliated with medical schools and should be exemplars of evidence-based medicine. Therefore, one would expect best practices to dictate when patients should be admitted to the hospital, how long patients should stay there, and how often they should see their physicians. If the practice of medicine varies so widely from one academic medical center to the next, they cannot all be right. For end-of-life care, the patterns of practice are based more on the accidents of local health care resource supply than on evidence; in other words, they are supply-sensitive. The degree of variation also suggests something else: that patients are receiving care and resident physicians are receiving training that reflects the local practice style of their teaching hospital.
As the 2008 Dartmouth Atlas of Health Care noted, "It is widely recognized that academic medical centers, particularly those associated with medical schools, have special responsibilities. They educate medical students and other health professionals, they provide postgraduate specialist training, and they play a leading role in continuing medical education. These activities constitute the clinical environments and role models that are essential for creating a professional identity, or sense of duty and standards of behavior for physicians. Academic medicine is also responsible for establishing the scientific basis of the medical care provided to aging Americans, most of whom will die from costly chronic illnesses that must be managed but cannot be cured." [4]
As Figures 3 and 4 show, in areas with more hospital beds and more doctors per capita, patients spend many more days in hospitals and receive many more physician visits. Figure 3 shows the relationship between hospital beds and admissions for the 306 Dartmouth Atlas hospital referral regions (HRRs), represented by blue dots (see Appendix A for details on how the regions were created). For many medical conditions, as the number of hospital beds increases, the admission rate (represented here as the discharge rate) increases. This graph shows that the available supply of hospital beds unconsciously influences a physician's decision to admit a patient. Conversely, the red dots at the bottom of the graph show that the rate of hospitalization for hip fracture is not correlated with the supply of hospital beds. This is because admission for hip fracture is effective care; the diagnosis is certain and medical evidence shows that hospitalization is essential for good outcomes. Therefore, regardless of the supply of beds, patients with hip fractures are hospitalized.
Figure 3. The relationship between the supply of hospital beds (1996) and hospital discharges per 1,000 Medicare enrollees (1995-96) among hospital referral regions
The supply of physicians also influences a patient's level of care. For example, Figure 4 shows that the number of visits patients make to cardiologists is positively correlated with the number of cardiologists in an HRR. This is because, at the regional level, cardiologists compete with each other for a fixed population of patients; therefore, the more cardiologists per capita, the smaller their patient panels, and the more frequently they see each patient. In the absence of clinical evidence surrounding the ideal frequency of physician visits for medical conditions (e.g., congestive heart failure or coronary artery disease), physicians' availability influences how often they see their patients for follow-up.
Figure 4. The relationship between the supply of cardiologists and visits to cardiologists per 1,000 Medicare enrollees among hospital referral regions (1996)
The high variation among the hospitals in Table 1 shows that clinical science to guide many types of medical care is lacking. Even the hospitals with lower utilization levels are unlikely to have a best-practice strategy regarding the allocation of resources that they could share with higher-intensity hospitals. Furthermore, physicians working within these hospitals are often unaware of nationwide differences in practice. [5] The hospitals in Table 1 ranking highest for most of the variables are located in New York City and Los Angeles, cities with high concentrations of hospitals and physicians per capita. The capacity of resources, along with established practice styles, dominates clinical decision-making and contributes to the higher utilization in these hospitals.