Diabetic patients with traumatic brain injury: insulin deficiency is associated with increased mortality.

BACKGROUND: Hyperglycemia after traumatic brain injury (TBI) is an independent predictor of mortality. Insulin deficiency, as opposed to elevated blood glucose, might be the reason for increased mortality. TBI patients with diabetes mellitus (DM) were analyzed to determine how insulin deficiency affects mortality after TBI.
METHODS: NTDB version 7 was queried for patients with isolated moderate to severe TBI (head abbreviated injury score [AIS]≥3 with AIS≤3 for other body regions). Demographics and outcomes were compared between TBI patients with insulin-dependent DM (IDDM), noninsulin-dependent DM (NIDDM), and those without DM. Logistic regression analysis was used to investigate the relationship between mortality and DM.
RESULTS: Overall, 51,585 patients with isolated moderate to severe TBI were analyzed. Mortality was 14.4% and 8.2% in patients with and without DM, respectively (p<0.0001). Although head AIS scores were similar, patients with DM had a statistically higher Glasgow coma scale (GCS) at presentation compared with patients without DM (GCS score 12.4 vs. GCS score 10.9; p<0.0001). After multivariable logistic regression analysis, DM was an independent predictor for mortality (odds ratio 1.5, confidence interval 1.29-1.74, p<0.0001). When comparing TBI patients with IDDM to NIDDM, mortality was 17.1% for IDDM and 13.0% for NIDDM (p=0.025).
CONCLUSION: DM is a significant predictor for mortality after moderate to severe TBI. Insulin deficiency is a likely contributor to increased mortality after TBI as IDDM patients have higher mortality than NIDDM patients who have higher mortality than no-DM patients.