Estimating Physician Effects on Glycemic Control in the Treatment of Diabetes: Methods, Effects Sizes, and Implications for Treatment Policy

Abstract

Objective: Researchers have only just begun to investigate physician-related effects on medical outcomes. Such research is necessary for developing empirically-informed practice guidelines and policy. The primary goal of this study was to investigate if glucose management in type 2 diabetes varies by randomly-assigned physicians over the course of a year in treatment. A second goal of the study was to investigate if physician-related effects vary across differential patient characteristics. The final goal was to provide estimates for patient-level effects.

Research Design and Methods: Hierarchical Linear Models (HLM) were used to investigate 1,381 patients, nested within 42 randomly assigned primary-care physicians. The primary outcome measure was change in Hemoglobin A1c (HbA1c) over the treatment year.

Results: Overall, physician-related factors were associated with statistically significant but modest variability in HbA1c change. However, physician effects varied by patient characteristics, mattering more for Black patients, patients over 65, and patients whose glucose management improved over the treatment year.

Conclusion: The results of this study suggest that differential physician effects have minimal impact on glycemic control. Results are particularly relevant in light of the recent movement toward patient empowerment in diabetes self-care and suggest a need for creativity and multidisciplinary collaboration in current treatment paradigms, with an expanded role for patient-oriented behavioral interventions.