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 A1c
(HbA1c) 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 HbA1c measured at least
once per year in 1992-1994 (n = 4744). Patients whose HbA1c 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 HbA1c measurements improved were
similar demographically to those whose levels did not improve but had higher
baseline HbA1c 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
HbA1c 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 HbA1c level
among adult diabetic patients is associated with significant cost savings
within 1 to 2 years of improvement.