Improved mortality rates in diabetic ICU patients appear to be independent of glucose control, study finds

Improved mortality rates in diabetic ICU patients over the past decade appear to be independent of glucose control, according to a new study.

Researchers performed a serial, cross-sectional observational study of adult, nonobstetric discharges from Yale-New Haven Hospital between Jan. 1, 2000, and Dec. 31, 2010. The study's objective was to examine whether decreased mortality affected all patients with diabetes and whether any factors could explain it. Main outcome measures were in-hospital mortality, inpatient glycemic control (i.e., percentage of days with glucose levels below 70 mg/dL [3.9 mmol/L], above 299 mg/dL [16.6 mmol/L], 70 to 179 mg/dL [3.9 to 9.9 mmol/L], and SD of glucose measurements), and outpatient glycemic control as determined by HbA1c level. The study results were published online Jan. 28 by the Journal of Hospital Medicine.

A total of 322,938 admissions were analyzed for the study, and of these, 76,758 (23.8%) involved diabetic patients. Among the 54,685 ICU admissions, the overall mortality rate was 9.9% (10.5% in diabetic patients and 9.8% in nondiabetic patients). Among the 14,364 ICU patients with diabetes, a 7.8% relative reduction in odds of mortality was observed for each successive study year, after adjustment for age, race, payer, length of stay, service assignment (surgical vs. medical), discharge diagnosis, and comorbid conditions (odds ratio, 0.923; 95% CI, 0.906 to 0.940). Patients without diabetes, meanwhile, had a 2.6% yearly reduction in odds of mortality (odds ratio, 0.974; 95% CI, 0.963 to 0.985; P<0.001 for the interaction). The significant decrease in mortality persisted in diabetic ICU patients after adjustment for both inpatient and outpatient glycemic control (odds ratio, 0.953; 95% CI, 0.914 to 0.994).

The authors speculated improvements in glucose management in the study may have been too small for a mortality benefit. Among other limitations the authors noted that clinical endpoints such as infections and complications were not included and postdischarge mortality was not examined. However, they concluded that the disproportionate decrease in mortality in diabetic ICU patients over time does not appear to be related to improved outpatient or inpatient glycemic control.

“Although improved glycemic control may have other benefits, it does not appear to impact in-hospital mortality,” the authors wrote. “Our real-world empirical results contribute to the discourse among clinicians and policymakers with regards to refocusing the approach to managing glucose in-hospital and readjudication of diabetes-related quality measures.”