Context: Although experimental studies show that insulin therapy can be safe and efficacious in improving glycemic control in type 2 diabetes under optimal conditions (ie, using patient volunteers with close monitoring under strict study protocols), little is known about its effectiveness, complication rates, and associated resource utilization in actual clinical practice.
Design: Cohort study.
Setting: Large staff-model health maintenance organization.
Participants: A total of 8668 patients with type 2 diabetes cared for by generalist physicians from 1990 through 1993.
Outcome measures: Resource use (hospitalizations, outpatient visits, laboratory testing, and home glucose monitoring) and glycemic control were evaluated using combined clinical, survey, and administrative information systems data. Detailed clinical case-mix data, including a newly validated case-mix method, the Total Illness Burden Index, were collected on a subsample of 1738 patients.
Results: Among patients starting insulin therapy, hemoglobin A1c (HbA1c) decreased by 0.9 percentage point (95% confidence interval, 0.7-1.0) at 1 year compared with those receiving stable medication regimens; however, 2 years after starting insulin therapy, 60% still had HbA1c levels of 8% or greater. There was no evidence that some primary care physicians achieved better results than other primary care physicians when starting insulin therapy in their patients. Patients with the poorest baseline glycemic control achieved substantially greater HbA1c reductions; those with a baseline HbA1c level of 13% had a 3-fold greater decline in HbA1c than those whose baseline HbA1c level was 9%. For a subset of all patients for whom detailed clinical case-mix data were obtained, those taking insulin had higher resource use than those taking sulfonylureas, independent of illness severity. After adjusting for age, sex, race, socioeconomic status, disease duration, and severity of diabetes and comorbidities, insulin users had slightly more laboratory tests performed, 2.4 more outpatient visits per year, and almost 300 more fingersticks for home glucose testing per year compared with sulfonylurea users (all P<.01). Although 15% of patients receiving insulin therapy reported weekly symptoms of hypoglycemia, insulin therapy was not associated with an increase in emergency department visits (after case-mix adjustment) and resulted in only 0.5 hypoglycemia-related hospitalizations per 100 patient-years.
Conclusions: For patients with type 2 diabetes who were cared for by generalist physicians, starting insulin therapy was generally safe and effective in achieving moderate glycemic control in patients who initially had poor glycemic control. However, insulin therapy was associated with increases in resource use and was rarely effective in achieving tight glycemic control, even for those with moderate control.