Effect of improved glycemic control on health care costs and utilization.

Context: Because of the additional costs associated with improving diabetes management, there is interest in whether improved glycemic control leads to reductions in health care costs, and, if so, when such cost savings occur.

Objective: To determine whether sustained improvements in hemoglobin A(1c) (HbA(1c)) levels among diabetic patients are followed by reductions in health care utilization and costs.

Design And Setting: Historical cohort study conducted in 1992-1997 in a staff-model health maintenance organization (HMO) in western Washington State.

Participants: All diabetic patients aged 18 years or older who were continuously enrolled between January 1992 and March 1996 and had HbA(1c) measured at least once per year in 1992-1994 (n = 4744). Patients whose HbA(1c) decreased 1% or more between 1992 and 1993 and sustained the decline through 1994 were considered to be improved (n = 732). All others were classified as unimproved (n = 4012).

Main Outcome Measures: Total health care costs, percentage hospitalized, and number of primary care and specialty visits among the improved vs unimproved cohorts in 1992-1997.

Results: Diabetic patients whose HbA(1c) measurements improved were similar demographically to those whose levels did not improve but had higher baseline HbA(1c) measurements (10.0% vs 7.7%; P<.001). Mean total health care costs were $685 to $950 less each year in the improved cohort for 1994 (P =.09), 1995 (P =.003), 1996 (P =.002), and 1997 (P =.01). Cost savings in the improved cohort were statistically significant only among those with the highest baseline HbA(1c) levels (>/=10%) for these years but appeared to be unaffected by presence of complications at baseline. Beginning in the year following improvement (1994), utilization was consistently lower in the improved cohort, reaching statistical significance for primary care visits in 1994 (P =.001), 1995 (P<.001), 1996 (P =.005), and 1997 (P =.004) and for specialty visits in 1997 (P =.02). Differences in hospitalization rates were not statistically significant in any year.

Conclusion: Our data suggest that a sustained reduction in HbA(1c) level among adult diabetic patients is associated with significant cost savings within 1 to 2 years of improvement.